Velocette articles - Velocette Owners Club

Compendium of e Group Articles
Collated by; Les Carman
24th January 2003
Velocette Technical Articles, Version 2.0
24th January 2004
Velocette Technical Articles
This document contains a selected list of Velocette technical information submitted by the
members of the Velocette technical e Group. It is further supplemented by technical articles
from the Velocette Owners Club website.
To go strait to the section place your cursor over the section heading below, hold the control
key down and left click your mouse.
Gearbox & Clutch
Fuel, Oil & Oiling System (for oil pump see Engine)
Frame (inc. wheels & tyres)
Cables & controls
Chains/Belts & Chaincase
Racing & High Performance
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Engine (for high performance tips see under Racing…)
#6 Recently we have had two different makes giving problems with seizure of inlet valves.
The Velo, a late Venom, fairly new to us, is almost certainly because the
the machined boss on
which the M38/4 valve spring bottom holder sits was badly cast, and is
Late heads are called "diecast" but in fact, the ends are formed possibly by
a die, but the central part is a core as in sandcasting. The boss is
offcentre laterally, and does not support the M38/4 properly on one side. We
welded and remachined, and hopefully this will cure the problem. The spring
tended to tilt the valve laterally when pressure was applied.
Hairpin valve springs are probably prone to the problem of different
pressures between the two individual springs. One answer might, at the top
of the valve stem, to make two demi-spherical parts to allow the springs to
tilt a little without transmitting lateral thrust to the valve. Or fit coil
springs, but make sure the seating for the spring, and the top collar, as
well as the spring, have perfectly parallel faces..
I have recently acquired a 1960 Viper - has anyone any comments on
how the valve lifter should be set on this bike?
#80 according to Ivan Rhodes' book your engine no. 16798 is from 1951
Rupert Banwell said in Ft 264 from June 94, "Useful information for rigid
MOV & MAC", that in 1951 from MAC 15982 the alloy engine was introduced
with either iron or alloy cylinder.
I have engine no. 18233 from 1952 with alloy cylinder head but iron barrel.(Walter Probst)
#81 My 1960 Velocette Venom is fitted with both the 0.010" and the 0.031"
compression plates on the cylinder base.
Prior to my recent engine overhaul the tappet adjustment has always
been at the end of the useful travel with the adjusters screwed right
through the rockers so that there is only just enough tappet left for
the nut to be tightened on.
have just renewed the valves, guides and springs and had the seats
recut. Very little recutting was required and the seats are in good
condition, ie not recessed into the head.
When I torque the barrel and head using the info on Dai's database I
now find there is noo adjustment left on the rockers at all.
Did Velocette just have one size of pushrod for engines fitted with
or without compression plates or was this considered unnecessary.
I could not find any data on the length of the pushrods to allow me
to check that mine are standard. Is this data available or does
anyone have a solution. The rocker arms are not significantly worn.
I can always get longer pushrods made up but I would prefer to
understand first of all why the problem exists.
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#82 I had a similar problem on the exhaust side of my Venom. On investigation I discovered that the
replacement Nimonic 80 valve was shorter than the original. This reduction in length was from the
collet grove the top of the valve. Apparently these were manufactured in this way to improve the valve
striking angle.
The effect of recutting the valve seats, and settlement of the compression plates will be positive
regarding your adjustment problem. Remanufacturing push rods is not difficult. Use 0.325 inch 16
s.w.g. tube (I have the spec somewhere if you need it)for the pushrods, you may need to ream the
bore 0.250 to get the spigots to fit in the bore. I used high strength retainer as well as a precaution.
By the way there is a simple lever tool you can make to help you lift out and in pushrods without
removing the rocker box. Get a steel bar about 18 inches long and on one end drill to fix a bolt about
3 to 4 inches long that will fit into the hollow rocker spindle. Then drill the bar and fix a shorter bolt that
will go under the rocker. You can then lever the rocker up and lift the pushrod up to get the lower end
out of the cam follower cup, so that you can slide it out of the push rod tube
#84 according to Ivan Rhodes' book your engine no. 16798 is from 1951
> production.
> Rupert Banwell said in Ft 264 from June 94, "Useful information for
> MOV & MAC", that in 1951 from MAC 15982 the alloy engine was
> with either iron or alloy cylinder.
> I have engine no. 18233 from 1952 with alloy cylinder head but iron
#96 I actuallly managed to track some pushrods down that were 3mm longer than mine that were just
the right size. I am now able to adjust the tappets easily, with plenty of adjustment to spare.
Incidentally I tried two different Velocette parts suppliers and their push rods varied by 2mm
#101 my white Venom Veeline - is running great. It has an Aussie piston
now, after problems with Omega ones, and the Total Seal rings (first time I
ever saw a 2 piece second ring!) give it the best compression I can remember.
The only time it has stranded me in 13 years and 30000 miles (since its long
sleep and reassembly) was when the infamous fiber gear stripped. It now has a
steel geared ATD like yours
#116 I'd love to know more details about the Aussie Venom piston and ring set you
Can you forward me details re-manufacturer etc.
#119 Aussie pistons because of problems with Omega ones ?
Sounds intersting. I dislike too a great extent those primitive Omega cast iron piston rings. Easily
identified by its charcoal black color. Just changing the oil ring to a modern 3 pc design cut oil
consumption to zero on my VMT. Modern chrome compression rings create then the required healthy
compression. But in recent times it proofed impossible to convince the local automotive parts dealer
to sell ring sets for just one piston. So where can I buy modern rings for Velo pistons, and if a
complete piston is needed, where can I buy them already fitted with rings of 2000 technology, not
1930ies ?
#120 A couple of you have asked, so here is everything I know about Velo pistons and
rings. I include the history so that you don't repeat my mistakes.
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Aka one rider's experience
Based on advice and experience from other local owners, when I reassembled the
Venom back in '88 I decided to scrap the original one-piece oil ring and use a
3-piece one. This seems to be a requirement when using modern oils. I found a
Toyota pickup motor (22R?) with the "same" ring dimensions and bought a set.
When I tried to fit them (not an easy task, the oil ring's expander is very
stiff) I soon discovered that the third ring land (groove) was too narrow by a
few thousandths. That's how I met Mike Parti, an incredible restorer and
collector (his favorites are pre-war - as in WW1) who turned the land wider for
me. This set worked fine until the top ring broke at the "top" punch mark and
destroyed the original piston. This happened 50 feet from the end of a 1000
mile VOCNA ride, I coasted in so it doesn't count as a breakdown!
After that I went through 2 Omegas in the original cylinder, each set to 6 thou
or more, and both seized repeatedly. I used the supplied top and second rings
and the Toyota 3-piece oil ring. With the cylinder now beyond last overbore, I
had another sleeved (the original was not cosmetically perfect, remember this
was a Veeline) and installed a used standard piston (Wellworthy), same rings
again. This lasted a couple more years until I got tired of the poor
performance caused by leakage behind the pushrod tube. Apparently the sleeved
cylinder would not stay round when hot. Honing, new rings, changing oil
grades, nothing helped.
On conversation with Ed Gilkison I found that the VOCA (down under) had
arranged for some pistons to be produced. Unfortunately, gentle readers, the
one I was supplied (.060" oversize, for a mighty 517 cc) turned out to be the
very last, and I have heard that no more will be produced. Dunno about MAC
ones. There is an alternative, however, so read on.
The advantage of the Aussie item is that it is made from a very low-expansion
alloy. It came with instructions to set up at 5 thou at the top of the skirt!
This gave a clearance of only 3 thou at the bottom, the normal measurement
location. It nipped up slightly when I gave it a bit too much stick during
break-in, but a quick pass on the Sunnen and at about 4 thou at the bottom of
the skirt it is fine. I didn't even change the rings, just filed the high
spots on the piston. 90 mph sitting up is no problem, and blow-by is minimal.
Ah, the rings. They are made by Total Seal, and the part number (remember,
these are 87.5 mm) is #C 3445 047 059 157 (TS1). My set was made under license
in Oz, but I suspect that a good racing equipment shop (check out
Streetfighters!) can supply them. They came with a hard chrome top, 2-piece
2nd, and 3-piece 3rd . Compression is amazing, cold or hot. You DU types (Mr.
Tesser) should contact your Tech Secretary if you need more info.
I turns out that many SoCal Veloista have ordered pistons from a local firm
called Venolia. They make pistons to order, and have copied the Venom design
(I think they have drawings for a MAC one, too). This is also done in
low-expansion alloy, and can be furnished with whatever style rings you desire.
Cost is not prohibitive. Their website is at Again, I have
not had personal experience here, but they come well recommended. And they
have not caused their riders any Summer Ride mishaps, to my memory. This is
the current crucible of Velo reliability, and quite amusing to watch when it's
not your bike!.
#129 Have just finished restoring a 1956 Mk II LE, and heard today that
the correct timing was with the timing marking holes coincident
(TDC), and the points just opening with the auto timing device
weights fully extneded.
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Surely this is incorrect?
When I set mine, I set it with the weights closed (retracted) and it
starts and runs OK.
Thanks for any advice
#152 I am thinking about fitting as one inch and a half carb to my
Thruxton which has been stroked to 580cc. I will be boring out inlet
to suit and have been given a MK2 concentric to try. Has anyone
fitted a larger carb to a Thruxton? If so what was the benefit if
#155 I have alternated between 1-3/8 and 1-1/2 GPs on my Thruxton (709cc). I have not opened up
the intake port in the head as flow bench testing revealed that with minor work around the guide area
and the best valve tulip shape netted 50+ hp flow potential with the 1-3/8 port. I would guess that
opening the port would only slow velocity and weaken the midrange (although some other 2 valve
street singles did come with the larger port, most in my experience will not outrun a good Thruxton,
particularly off the corners). Instead I have the 1-1/2 inlet manifold tapered down to 1-3/8 at the head
which is common practice on newer long inlet tract designs.
I tested a bunch of carbs (GPs, Mikunis, Delortos, Concentrics, etc.) and couldn't find anything with a
needle in the middle that would match the GP for all out flow. Others may help mid-range though with
better part throttle metering than the broom stick that the GP uses for a needle. I believe there are
two different Mark 2 Amals, standard and smoothbore. I think you will find a standard 38mm (1-1/2)
Amal will not flow any more air than the stock 1-3/8 GP. The smoothbore might a bit.
The stock Velo exhaust port is terrible, you should concentrate more effort there....
The seat of the pants difference between the two GPs on mine is negligible. I'm going to be trying a
40mm Mikuni flat slide in the near future but the sight of that thing sticking out the side where a GP
used to be doesn't excite me any! Maybe the power will.
#156 Re: Stewart's question on larger carb's on Thruxtons. Paul Zell has a 1.5"
GP carb on his 720cc monster Thruxton, and it works just fine thank you.
Mind you, his engine is a lot bigger than your measley 580cc (MSS crank?)
item - and as a consequence he's done a lot of work beefing up the drive side
of the custom cast crankcase. But not even a Manx used a GP that big, and
made plenty of power. But then again, Italian racing singles use monstrous
carbs for top end breathing - they must have been useless at low rev's.
Don't expect a big increase in the top end unless you have a very good tuner
doing your porting!
And see the related article on the Big Johnson motorcycle.
Re: clutch chainwheel bearing (not throwout bearing) life with a belt drive.
There will always be some oil in the primary from the engine breathing
through the main bearing. I think we should ask someone who's put some miles
on this system, though, to find out if it's enough. Those bearings sometimes
are in short supply! And as a sidebar, on the throwout bearing, rollers are
the only way to go. Two sets of the ball type wore out in 3 years on my VMT
before I got wise, and have never had to change them since (this is 12 years
ago). Paul
#177 (LE Model) The timing settings for all engines I know of are quoted as "full
advance" i.e. with the ATD springs fully extended. This will give a
setting which when using the design intent fuel will produce an
approximation to maximum available torque at all engine speeds, while
keeping clear of damaging detonation limits. If you set your ignition
timing on full retard i.e. with springs in closed condition, the
effect will be for the engine to run with excessive spark advance
which may improve torque, but only if the optimal spark timing has
not already been reached. The trouble is that the increased advance
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may also cause the motor to run past the detonation limit at some
Modern pump gasoline (even unleaded) is generally much improved on
the equivalent available in 1956, so it is possible that the LE might
stand a little more advance, but the only way to tell for sure is by
running spark sweeps on a dyno.
Remember too that ignition systems of this era were very primitive by
modern standards and are only capable of a small amount of automatic
advance which will retard spark at low engine speeds and reach full
advance at around 2500 - 3000rpm. With modern engine management
systems it is possible to calibrate the system to run the ideal
amount of spark advance for all running conditions e.g. speed, load,
throttle opening, engine temperature, air temperature, even making
adjustments automatically for whichever gear you happen to be using!
With our old things spark timing can only ever be a compromise, and
was specified to provide the best performance while keeping within a
safe running condition. In light of this, unless you have the
facility to find out otherwise, stick with the factory recommendation
and set up with the ATD wedged in the full advanced position.
Happy riding,
Pete C.
#187 your interpretation of the instruction
appears to be correct in that you are told to set full advance at
TDC. I can only assume that the engine is extremely det limited if
this is the correct method. If on the other hand the method should be
to set to full retard at TDC, i.e. with bob weights closed, then the
only control on the critical full advance setting is the amount of
advance provided by the ATD, again a fairly primitive device which
was likely to have had a tolerance of a few degrees of range even
when new, never mind after half a century's use!
#198 Tony described the correct way to fit an oil seal to stop oil exiting the main bearing – now I will
describe a “bodge”, that a fellow club member used to fix the same problem.
Clean the inside of the sprocket with alcohol or some other solvent, place a circular bead of silicone
around the part of the sprocket that abuts the main bearing boss. Smear light oil on the main bearing
boss, slide the sprocket on and rotate at least one revolution. Lightly screw on the shock absorber,
spring and nut. Leave it for 24 hours, before reassembly
#201 I have a 1955 MAC which I am building at present and as some bits
were missing: rims, mudguards, seat etc, I am doing it as a street
scrambler with 21" front wheel and 18" rear, stainless guards and
Thruxton seat.
Looking at the inlet valve guide yesterday and being slightly bemused
by the fact they are straight sided. Obviously another Velo
idiosycracy. I started to think about valve guide seals. I also
happen to own a Armstrong MT500 with the Rotax 500 engine. Believe it
or not the Rotax valve guide seal fits the MAC inlet guide.
Anyone got any reason that this might not be a good idea.
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#202 I have never had a problem with burning excess oil via the guides on a pushrod velo. Restricting
oil to the guides (particularly the exhaust) may cause the valve to seize. But if you want try it – let us
know what happens!
#203 I second Dai's concerns - I had an intake valve seize some years ago, it wa=
s a Manley SS intake in a silicon-bronze guide. The clearance was per the R=
ed Book, and no seal was fitted. It just picked up some guide material on t=
he stem, which was removed with emery cloth and the Venom took us home the n=
ext day.
Methinks there is precious little oil in a pushrod Velo rocker box to begin=
with...and it has a hot, brutal life...
#205 Contact The Cylinder Head Shop.
They have a technique of swaging a centre into the guide. The guide has
lateral corrugation which hold the oil and allow finer valvestem/guide
clearances to be used
#212 I would really like to set up an airbox/filter for my '56 MAC which has the usual short open
bellmouth on the 376 Monoblock. Putting any kind of even light foam over the bellmouth breaks up
airflow and causes the bike to run lumpy. I live in the desert area around Carson City, Nevada, so an
airbox would probably add considerably to the engine's longevity. Any suggestions out there?
#213 I have a foam sock on my 52 alloy MAC,
bought at a dirt bike place. Works, but
you may need to rejet. There is not a
lot of room between the carb mouth and
the oil tank. The original Velocette
aircleaners had a rubber tube leading to
the aircleaner between the back of the
oil tank and the battery. I don't see
that this would give any better air flow
to your mono block than a sock, but it
would probably look a lot better. I have
seen variations on this, a rubber tube with
a sock on the end..
I also have a K&N flat round filter on
my Endurance which is perfect.. just fits
with some force between the oil tank and
the carb. I had to reject for it as well, but
it is like other K&Ns.. not much restriction.
I understand that these are no longer
available, I got it with some parts I bought.
I have seen modified Triumph style filters
fitted to Velos.... if you are handy with
body work.. I think you need to start with
one with hole for the carb in the middle.
Mike Jongblood has one on his 500, you may have seen it.
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#217 I have a standard 1960 Venom which has had the piston rings and valve
guides and valves replaced. This was only about 100 miles ago. I am
having problems with the spark plug oiling which may be due to the
guides and the slightly rich mixture. However it did that before I
rebuilt the engine.
I have used Champion N3C and NGKB8ES plugs although the NGK ones seem
better. However, even that let me down coming away from a classic
bike show, about 30 seconds after I had started the bike. Very
embarassing as I was being critical of all the competitors who were
loading their bikes onto trailers.
A fellow competitor lent me a plug which had a centre electrode that
protruded more than the plugs I normally use. It got me home and
still had a big fat spark when I checked it out.
Does anyone have any suggestions as to whether I should use a hotter
standard plug, go for an equivalent plug with the protruding
electrode or try to deal with the cause (if there is one) or the
#219 Thanks for the air filter info. I will be at the opener. I have come across one of the BSA/Triumph
pleated paper air filter elements, about 4 1/2 inches by 2 1/4 inches. I have some great firm plastic
sheeting to adhere to both sides of the element, cutting an opening for a short rubber spigot to apply
to the 376 Monoblock after removal of the dinky bellmouth, which, aside from protecting the threads
on the carb is probably technically useless on the MAC at it's normal driven speeds. I think it will
breath quite well, but we shall see. Need a project right now, anyway. I have already dropped the
main jet to a 180 from the stock 200, which at this altitude of about 4700 feet cleaned up the mixture
nicely. Now, If I choose to open the throttle to the 3/4 to full open position, the engine doesn't bog
down. Must remember to rejet when I get closer to sea level. Running a B7ES.
#218 In my 67 Venom I have had excellent performance from NGK B7ES and BP7ES, the
latter has the projected electrode. Unlike some other brands, you can decipher
NGKs as follows:
B means 17mm threads
P means projected tip
7 is heat range, higher is colder
E means long reach (iron head MAC takes H)
S means standard materials (not platinum, etc.)
At high altitude (over 8,000 feet) I have also used B6ES successfully.
#219 I run a small foam air filter on my Venom, yes it required minor rejetting. I
run a main one size down from the 270 specified for my Concentric. It has the
spring. The light green Uni's filter better but flow worse; I'm using a dark
grey one.
If you have never seen a stock air filter like the one Paul has offered you
would not believe that it actually flows enough air. There is a short rubber
adapter (<1"long) connected to an "ear" on the main filter housing that looks
inadequate even for an LE. The filter itself is coarse steel wool, intended to
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be oiled. However, proving yet again that Velo had it right, it did not change
jetting. It would probably work fine on your swingarm MAC
#223 At last year's Stanford Hall Rally my Venom did not want to start.
After I had exhausted myself a volunteer from the inevitable crowd
that were watching finally managed to get it going. On kicking it
over, it had now developed a habit of spitting back enough neat
petrol for it to be seen running down the oil tank. It got me home OK
and ran well at higher revs.
After repeating this performance a couple of times I tackled all the
obvious things, plug, BTH manual magneto points, pickup etc. with no
joy. I then changed the carburettor, from monoblock to concentric.
This was easier to start but ran lumpily at low revs and this time
spat a small quantity of neat petrol back through the carburettor on
each firing stroke; again it seemed to be OK at higher revs.
Getting more desparate I have removed the cylinder head to find no
problem with the inlet valve or seat. I have taken off the timing
cover and found the cams, followers and gears all to be in apparently
excellent condition.
What next?
#225 I had the same problem on my 58 Venom, after fitting a new Monobloc.
Spitting back at low revs indicates richness, which is controlled for
the first quarter of throttle movement by the Pilot Air Screw. Try
screwing it out a little at a time (to weaken the mixture) until the
spitting stops. You may have to adjust the throttle stop afterwards
to obtain a satisfactory tickover.
#228 One of the major reasons for a Venom spitting back is due to the large amount of valve overlap
that a M17/8 cam gives. If you check out most Venoms after a run, you will find petrol and oil debris
on the oil tank that has been jettisoned from the carb. A MSS with a softer M17/7 doesn’t suffer from
Check your valve timing, remembering to use the increase valve clearances. You will find that the
timings will not be spot on mine were 65–39–50–55 rather than the 65-35-45-55 as specified. If yours
are out you can spread the error by moving the cam a tooth either way to see if it helps
#231 Can anyone give me the dimensions for a megaphone for a tuned 500
and/or recommendations for a Supertrapp type 'silencer'?
#233 Do I win a prize for spotting that the desmo setup on the front cover
of Fishtail 323 shows that the exhaust cam follower appears to have a
roller on the rear follower instead of the usual "slipper" I have an
article from Motorcycle Mechanics 1962 which shows ALL to be slipper
type. Does anybody have any knowledge about this apparent variation.
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Does anybody have the fitting instructions or a copy as supplied by
BMG. Is there anybody out there still alive from the BMG days who
could give some advice/clarification? Lets hope so on all counts!!
There was a firm in California called "BHB Cyclery" Do they still
exist? They used to advertise BMG desmo stuff and were advertising as
recently as August 2001, but alas not desmo gear, but a Thruxton so
equipped. Do any of our American friends know the answer
#234 I have seen two sets of BMG kits here in the us outside of a bike, and know
of one VMT with a kit installed. The two I've seen had the skids not rollers,
and I'm not sure rollers would work due to space considerations. Remember,
they follow the cam on both top and bottom, in a 'c' shape. One of the
uninstalled desmo kits was very interesting, as it had broken a pull-rod and
wreaked havoc; the diameter of the rods was quite small, only slightly bigger
than a GTP oil pump rod (there's your Velo memory test).
From what I've heard, there was essentially no difference in performance
between the BMG kit and standard. BUT the Thruxton locally with the kit
installed held a speed record at Bonneville, and I think I recall seeing a
period road test showing a BMG-kit Thruxton lofting its front wheel(!).
Ed Gilkison has a kit which he's studying for possible reproduction; bug
him about it if you want one!
#235 Can anybody help out with correct main jet and needle sizes for a
Amal concentric R300 932 fitted to a 57 MSS. The bike used to run
like a dream until I recently replaced the silencer since the baffles
had fallen out of the old one, I can only find details for a Monobloc.
#236 The attached information is courtesy of Phil Irving. The pipe lengths tie up with the carburettor
settings for different exhaust systems given towards the end of the “Red Book”
#243 I am the proud owner of a 1967 velo Thruxton complete with GP carb ,
but on touring in this area of Holland thats no fun, Can somebody help
me with spec of another carb like Amal Mark 2 or Dell'orto which size
and the spec thanks.
245 I suggest you order your MkII concentric from R. F. Seymour’s, the last price I had from them was
approximately 150 euros. The benefit of ordering it from them is that they will be able to provide you
with lots of set up advice based on experience. They also sell goodies to go with it such as manifolds
to clear a standard Clubman tank. Their number is +44 1844 212277
#247 My 376 series Monobloc for my '56 MAC seems to be somewhat worn, either ob the slide, body,
or jet body. If I decide to go for a new Monobloc, would Seymour's be my best bet also, living here in
the colonies, or where else would you suggest? I could get a new slide and jet body from Domi-racer,
but feel like having everything matched from the outset might be a better idea..
#250 You will be surprised how a new carb will transform the starting and overall running of your Velo.
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The Monobloc was a standard fitment on a MAC, so information on set up is available. The MKII on a
Thruxton is not so strait forward. Therefore where you get your Monobloc from is not so critical
regarding after sales support
#254 I have used an Amal Concentric mk1 # 1036 on my Thruxton for many years,
with a reliable slow tickover and generally very good performance. The only
downsides are; it needs a mighty tickle to start from cold (lots of gas on
the ground), and the idle air inlet must be opened out a little for the
transition from idle circuit to slide cutaway(Frank Forster wrote an article
on this, I'll try to post it here). The upside to this carb is that it looks
'period' on the VMT, as it's basically a 60's body, whereas the Mk2 Amal or
Dell'Orto looks like a Japanese fitment.
The 1000 series Concentric carb's were originally made for Spanish two
strokes. For some reason the bodies are made of real aluminum, not Mazak
like smaller Concentrics, and as a result they last quite a while. I have
put tens of thousands of miles on my VMT (maybe 40-50k, don't know exactly as
I ran through 4 sets of magnetic instruments before I got wise and put a
chronometric speedo/tach set on 6 years ago), and am still using the same
body and slide, without an air cleaner.
I'm sure if you do a little footwork you could find one of these carb's
n.o.s. Make sure it is correctly 'handed' on for a Thruxton, ie
tickler/adjusters on the right side.
#264 What methods have members of this group used to overcome slack
oil pumps in crankcases? I have just come across this with an engine
I am building out of autojumble parts and I am thinking of having the
main oil pump body hard bearing chromed, anyone any comments.
#268 I got a "new" monobloc from Surrey Cycles and have been pleased with
it. I had excellent service from them and they also do mail order.
Check it out on
#272 Help/advice required from any LE cognizants
I have twice had teeth broken from the camshaft gear of my 1956 Mk 2 LE.
I could find no reason for the first breakage, except that the gear appeared
to have had a broken tooth repaired on some previous occasion and
perhaps the repaired tooth let go and the bits took out a few of its
I then replaced the gear with another which appeared in very good condition,
but which had come from an LE which had burnt.
Within 50 miles, two more teeth broke on this gear, one of which was in the
same relative location as one of the first. There is no evidence of any
seizure of the camshaft or tappets or valves, the pinion looked in worn but
reasonable condition, valve springs not spring-bound, valve heads did not
hit the heads.
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In the second case, the two broken teeth were on opposite sides, i.e., 180°
apart, leading to my thinking that the first broken tooth had jammed in the
pinion and done one rev to hit the opposite tooth, just a surmise.
The teeth are broken at the point of the camshaft rotation where the exhaust
valve is in the fully open position.
I am looking for a replacement set
#273 If you want to update with a practical solution for everyday use with a modern
carb I would suggest contacting Phil Allen at:
Allens [email protected], Unit B9, Moorbridge Road, Bingham, Notts
Tel 01949 836733
Fax 01949 836734
Open Monday to Friday 9 to 5, Saturday by prior apointment
Phil has Mikuni alternatives with suitable base setup and a good supply of
spares should they be needed.
.#281 Hi, What methods have members of this group used to overcome slack
oil pumps in crankcases? I have just come across this with an engine
I am building out of autojumble parts and I am thinking of having the
main oil pump body hard bearing chromed, anyone any comments. Stewart.
The only method I have come across but never used, is to sleeve the crankcase – a skilled
engineering job
#313 Has anyone got to hand the Valve timing figurs for a MK8 D.O.H.C.
works engine?
#349 I acquired an Amal mk2 38mm from Seymour and the bike starts better
than with the Gp mounted, but runs lumpy too rich stationnary.When I
rev the engine it goes but when you close the throttle the engine
runs too long on, then after a while it dies. On idling speed when I
oen the pilot jet more then two turns the engine runs faster so it is
too rich on pilot jet. The question is has someone settings for the
#364 You can use grinding compound on a plate glass plate to remove the wear on the oil pump
base, but I would expect a surface grinder to do a more efficient job.
The only other problem I could think of, was if the pump was slack in its bore then when the
crankcase warmed up the differential rates of expansion may allow air to be sucked into the pump.
However I feel this would be unlikely.
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#369 Anybody know how to get the flywheel off a two stroke? The engine
freed off in my U last night, but that now means I can't lean on the
stuck piston to undo the flywheel nut. My reading of the engine
section drawing (on is that the nut acts as an
integal puller - or am I way off the mark?
Also discovered that the Mag appears to have automatic advance hence no cable for it. Despite standing for 50 years it still gives
a (feeble) spark.
#370 I am not familiar with the model U but I did own a GTP. I believe the nut is separate from the
pulley/flywheel/sprocket assembly. If the engine is in the frame and the transmission is still intact, try
putting it in gear and applying the back brake while trying to remove the nut. It may work but no
#375 I'm rebuilding a 1957 MAC and have a couple of problems that I would
appreciate some advice on.
It has suffered a fair amount of neglect, and the oil pump (which I
have removed)feels a little 'rough' turning it by hand. Is it a very
specialised job to rebuild these or would a secondhand one be more
If the latter is the case, anyone out there got one for sale?
The other problem is that, at some time in the engine's life, the
main bearings have been turning in their housings, causing some
slight damage to the faces. The current bearings are in good
condition, and the outer races feel tight in their housings. I have
heard that one can use Loctite in cases like this, or have the
housings machined and fitted with inserts.
#377 The pumps themselves aren't that difficult to
overhaul.The trick is getting the components lined up so
that the pump turns freely and then goes back into the
case without wrecking the bore.If you're unsure,take it
to someone who is.I think I would take the pump apart
before I bought a new one and assess the damage.You may
find that it's only minor damage.As far as the cases
go,again take your cases to someone with experience in
that area.I'm sure the problem isn't that bad,but you
don't want to put the engine back together until you've
verified it.I am not a big fan of locktite on main
bearings.There's too many things that can affect
adhesion.The better way would be to bore and sleeve the
mains back to standard.
#378 Please read the manual. There is a special "clamp" tool to line up the oil
pump casings. The removal and replacement of the pump assembly required the
heating (carefully) of the crank case to allow the differential expansion of
the two dissimilar metals to release the pump. Always bolt the two halves of
the crank cases together to prevent distortion. Brute force and ignorance
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will result in damage to the oil pump drive spindle and the crank case
housing bore.
#380 Thanks for the reply. I discovered that the pulley was just bolted
onto the flywheel - a home mod I think! The nut does however act as
a puller for the flywheel, and I was able to both undo the nut and
break the taper faily easily by jamming the crankshaft against the
conrod with a block of wood. Unfortunately I think I moved the
flywheel round, so now have no idea where the Mag was timed at, but I
am sure there must be a fairly easy way to re-time it when it comes
to rebuilding the engine
#422 Where is the number usually stamped on a head? I just want to make
sure what I am looking at is Venom and not MSS. Any other quick
visible or measurable differences.
Also an article in a Fishtail some years ago mentions a Crankcase
breather alteration. It described how to do it, but had no technical
info with it. It says, Drill a half inch hole behind the camwheel
from the timing chest into the crankcases. Drill a 1/4 BSP hole below
the magneto and insert the adaptor M275. I would quite like to do
this, but would like perhaps a few more acurate measurments before I
attack my valuable cases with the pillar drill. Has anybody done it?
or can provide some measurements.
The article was written by James Plant.
#426 The MSS and Venom head is identical apart from the inlet size. MSS inlet is
1 1/16 inch, Earley Venom is 1 1/8 inch, most Venoms are 1 3/16 inch. The
early MSS also had 5/16 inch cylinder bolt holes..
#431 Since the main bearings failed in my `54 MAC after getting back from
Barvaria last year I haven't been able to get the bike to run properly.
I've had a number of problems including nipping up a piston since, possibly
I have discovered, in the course of investigation, that the bike has an
M17/7 cam and followers as fitted to MSS and early Viper. Has anyone else
got an MAC with this cam? If so is the cam set up according to the marks on
the wheels?
I've checked the cam timing with the valve clearances set to 30 thou inlet,
35 thou exhaust (as specified for the MAC). The results are as follows
(M17/7 spec in brackets) :Inlet opens 25deg BTDC (19deg) - opens early
Inlet closes 50deg ABDC (49deg) - closes late
Exh Opens 50deg BBDC (49deg) - opens early
Exh Closes 16deg ATDC (19deg) - closes early
I've tried taking cam lobe centre readings but as I haven't got a dial gauge
it proved to be difficult to be accurate enough to perform the check.
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Can anyone comment on whether I have the valve timing right or not? Should I
get a dial guage and do the cam lobe centres?
This is driving me mad. My MAC used to be an easy starting good performer.
Now it doesn't start well and coughs back through the carb.
#433 Just a further thought - the MSS with a M17/7 cam has ignition timing 36deg
BTDC fully advanced. Does the ignition timing follow the type of cam ie. if
I'm using an M17/7 cam (MSS type) in my MAC in place of the M17/5 (MAC
type), should I change the ignition timing from 38degrees to 36 degrees? I
have a sneaking suspition that I should.
This is most perplexing. Before the recent problems the bike ignition timing
was set by the roadside, after yet another ATD spat its fibre teeth, using a
piece of stick found at the roadside with a rough estimate of about 11mm for
the piston crown distance BTDC. The bike has been running fine ever
since:-)) I've never used a degree wheel until recently. Precision
measurements ain't what they are cracked up to be.
Going to get a dial gauge and check the cam lobe centres.
#434 You might check your ATD to make sure that the springs are still
okay, I had one break once, the ATD went into full advance. Velos
are very sensitive to ignition timing, less so to cam timing. But
the timing at full advance won't affect starting much.
If you want to check the cam timing on a /7 with VM/MSS followers you
should use 50 thou clearance as specifed for the cam. This should
yield numbers closer to the spec. Also, it is not well documented
but there is more lift on the 86mm cams, a /8 has 20% more at the
lobe than a /4. I don't have the others handy to measure, but I'll
bet the /5 and /7 also have different lifts. Uh, Dai?
Zuma's '56 MAC was very easy to start and performed fairly well, too;
it proved to have a missing piston pin circip and the bore was deeply
scored by the pin. A fresh bore, a bit more C.R. and it is a finicky
starter now. The crankshaft must be in exactly the right spot or it
backfires badly.
#435 Thanks for the note. I had already tried checking the cam timing with the
50thou gap and ended up with crazy readings. Last night I read the MSS
Maintenance Manual I have and it said check with 30thou gaps (the MSS used
the M17/7 cam). I tried this and the cam timing came out to within one
degree of spec as I have it set up. I also got hold of a dial test indicator
and checked the dwell and calculated the cam centre point. That came out to
within half a degree. I doubt that it could be adjusted closer than that. At
least thats one thing sorted out.
The bike won't start at the moment. It has good compression (for a re-ringed
motor) and a fat spark at the plug. I am beginning to suspect that the fuel
has gone off. Its possible that it could have been there the best part of a
year. When the bike started on Tuesday it was coughing/spitting back through
the carb a lot, particularly on small throttle openings (ie while trying to
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start) indicating, I think, that the mixture is weak. I blew out the idle
drillings yesterday but now it won't fire up at all. If the fuel has
separated and/or the volatiles have evaporated then surely that would make
the fuel calorific value lower hence the mixture would be weak (higher air
to fuel energy ratio)? Does that make sense? Maybe the small amount of fuel
in the float bowl was still good and once that had been used up the
remainder was bad?
Anyway, tonights job is to get some fresh fuel, drain the tank and carb and
try again. I hope thats what is causing the problem but I've never
experienced petrol going off (although I've heard others talk about it).
The ATD springs are OK. The ATD was overhauled a few years ago with a new
fibre wheel and springs. I have set the mag timing to 38deg BTDC fully
advanced. The MSS manual says 36degrees BTDC. I wouldn't have thought that
this would make too much difference to whether the bike would start or not.
#436 I have had similar problems with my Venom recently ( see earlier posting on
'spitting' ). After repeated checking of valve and ignition timing, cleaning
out of carb jets etc. without benefit, I changed the carburettor to an old
spare. Hey presto the damn thing ran as well as ever. I suspect that the
float height was wrong.
#437 I have had similar problems with my Venom recently ( see earlier posting
> on
> 'spitting' ). After repeated checking of valve and ignition timing,
> cleaning
> out of carb jets etc. without benefit, I changed the carburettor to an old
> spare. Hey presto the damn thing ran as well as ever. I suspect that the
> float height was wrong.
> Persevere and you will be rewarded!
The bike was fine on the existing carb before I took the bike out of service
to change the main bearings (this time last year). I'd just returned from
Germany on it with no signs of bad running.
I'm going to change the petrol for some fresh tonight and see if thats whats
causing the problem. The bike has always been a good starter and an easy
ride. I miss it and want to get it sorted. I will persevere!! I'll check
that the float bowl is filling OK as well..
#442 Well, I found the reason the MAC wouldn't start - the ATD had come loose.
Idiot!! I had checked that there was a spark at the plug and it seemed fine.
Anyway, now the bike is running again there seems to be a lot of noise from
the timing chest of the engine. My Haynes says that if the intermediate
timing gear is only in shallow mesh then the symptom is a mechanical
clacking noise. If I turn the engine over by hand this is what I hear. Has
anyone else experienced this? I plan to check the mesh tomorrow evening and
if necessary adjust the intermediate timing pinnion..
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#444 My 1967 edition of the Red Book lists 30 thousandths checking clearance in the
Data section (p.7), but the Sports/Clubman Preparation section (p. 102) states
that "Greater accuracy of reading is obtained..." using 53/52 thousandths, with
identical cam timings. Anyone care to comment?
There is a shortcut, though - courtesy of a "Molegrips and Hammers" article in
an old FT:
For fairly obvious reasons, both valves should be equally open at TDC (of
course, one is actually closing). That is, at TDC the rocker arms are lifted
equally, which is easily verified. The actual limit on accuracy is finding TDC
in any case. This has worked acceptably with the /8 in my Venom, not needing
adjustment in 25,000 miles.
#446 Quite obviously something wrong here. Greater accuracy may well be obtained by
using a wider clearance when checking because you will be on a steeper part of
the cam, but the timing will of course be different - with wider clearances the
opening time will be later and the closing time earlier. It is for this reason
that I prefer to check the peak lift point when checking cam timing. If you
assume the cam to be symmetrical, which they normally are, then this is easily
worked out.
As regards finding TDC accurately this can be done easily to less than half a
degree if you use a positive stop for the piston when setting up the degree
disk. An old plug can be easily modified to do this by carefully cutting round
the steel body just above the hexagon and removing the insulator assembly.
remove the outer electrode and tap 10mm x 1.25 through the body. Fit a 10mm
bolt around 60mm long into the body and file or grind its end to a nice rounded
profile to prevent damage to the piston and you have the tool. Remove your
spark plug and rotate the engine so the piston is in the lower half of the
stroke and fit your new tool in the plug hole, tightening gently. fit your
degree disk and pointer and rotate the crank slowly until the piston is hard
against the stop and take a reading on the disk. Turn the crank back until you
are hard against the stop in the other direction and take another reading.
Using the two readings set the pointer to read equally either side of TDC when
the piston is against the stop and you have a very accurate setting which
accounts automatically for any.
#448 It seems obvious that increased clearances change timings, but as we
all know, the Red Book is never wrong!
M17/5 and /7 cams are fairly symmetrical, but the /4 and /8 are far
from it, with a much gentler opening ramp.
The beauty of the "Rastus" trick is that it requires no degree wheel.
I have a tool that measures piston position, it is a sliding scale
in a holder that is threaded for the spark plug hole. It makes
finding TDC to within a couple of degrees quite simple. One tooth on
the cam gear is four degrees; no better accuracy is available unless
you are willing to disassemble the cam from its gear. This may make
your racer a tiny bit quicker but is not needed on a street machine.
#449 My Red Book (for the swingarm models) shows a 10 degree difference between /8
cam timing at .030 and .052 lift.
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One tooth changes the valve timing 8 degrees at the crank, where timing is
measured, and it is certainly noticable. Carefull with piston clearance,
particularly the intake valve when advancing.
The lever action followers create much more action on the opening side, so
although the ramps on the cam are different, actual valve rates are probably
much closer to symetrical than it appears, I've never graphed it though.
If timing for split overlap gives correct timing when measured at .030-.052,
then the valve action can't be symetrical. On a /8 cam, assuming the timing
was symetrical, lobe centers based on the book would not be the same, more
like 95 and 105 degrees..
#458 I've just got a +60 piston for my MAC from Founders Day today. I measured
the skirt and compared it to 68mm +60thou which gives approx 5 thou skirt
clearance (or about 2 thou per inch). Does this sound OK? Too big? Its an
all alloy engined 1954 MAC.
I was wondering if it is possible to use an iron cylinder in an alloy motor.
#459 I have a MAC from 1952, rigid, AL-engine, but with an iron barrel. The engine
sounds very good. I didn't know if this was original or something put together
later. Then I found in Fishtail 264, page 30-32, "Useful information for rigid
MOV & MAC", where it was said under "Engine, no. 6: Alloy engine with either
iron or alloy cylinder introduced 1951 (from MAC 15982). This engine had split
skirt piston."
So that's the point, either ironor alloy cylinder. It works. When Velo
introduced the AL-engine they obviously worked up all the stocks of iron
#460 Give Tony a call at Hartlen engineering, he should help you. Tony has been
reboring motorbikes for many years including doing a lot of work for Geoff
Dodkin. I took my MSS barrel and piston to him, and before I even spoke he
correctly identified what it was. He also does cylinder sleaving at what I
think are reasonable prices.
His number is +44 (0) 1483 202540
#489 has anyone had any problems with
venom/viper thru studs, that hold the head and barrel down. i just
bought a venom off a guy and when he fired it up it started to blow
slightly at the head. this confused me a bit as velos dont do that.
the holding down method is execelent and i have never known it
happen.i got to thinking about it and i asked the guy if he had used
stainless instead of the originals, he replied yes he had. i have
seen this before with guys with triumphs and bsa's the stainless
application doesnt seem to be up to the job. i would guess that the
original material would be a good grade tool steel and the stainless
would be an unknown quantity. could anyone please give me any
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feedback about this. i took out one of the studs to examine it and i
noted that the nut was direct on the head. Should
#492 Stainless engine studs are known to work loose. There should be a washer
under the Nylock nuts, and normally (but not always) there should be an “O”
ring underneath.
#493 would you recomend using the original studs instead of
the stainless items, ?. i have zinc plated the originals and was
considering putting them in. what do you think.? does the stainless
studs reqiue a bit more tightning ? i belive that they were pulled
down to 24lbs originally.
#494 The original studs and one hopes the Velo replacements would have been
calculated to "do the job".
Stainless steel used id free machining, normally A2 and one would suspect the
UTS (Ultimate Tensile Strength) would be up to 50% less than the original
steel studs.
People automatically think stainless steel is stronger.
Change them.
#495 The original studs and one hopes the Velo replacements would have been
calculated to "do the job".
Stainless steel used id free machining, normally A2 and one would suspect the
UTS (Ultimate Tensile Strength) would be up to 50% less than the original
steel studs.
People automatically think stainless steel is stronger.
Change them.
#496 I wouldn't recommend exceeding the factory torque specs for stainless or
other studs, the consequences are a lot more vexing than re-torquing the head
or replacing the studs themselves.
I've found that a Velo, or any other bike, left sitting long enough in
conditions where there is a cycle of heat/cooling, like normal
daytime/nighttime cycles, will loosen its nuts up. This is most dramatic in
hot climates, obviously not as much of a problem in England!
It sounds like the bike in question with stainless studs is more in need
of the proper nuts and washers than new studs.
#497 There is very little difference in elasticity and thermal expansion between
various grades of steel (including most "stainless"), so torque specs should
not vary either. A higher tensile strength only allows more torque, not needed
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here. The failure mode would be a broken or stretched stud, which I've never
heard of in a Velo. Stripped, yes. Make sure you oil the threads.
The key is using the correct washers, they are thicker and hardened. The
O-rings help against leaks, as do Nylock-type nuts.
If you kept the C.R. down maybe your nuts would stay tighter,
#498 316 by which Ron probably means 316 S16 is a very superior stainless to the
commercial A2 which is more a kin to 304 S31.
316 S16 has good strength and creep factors. It is also the material used
extensively by us in ships.
So if you drive your Velo into the sea the bolting will be OK.
#499 Agreed, The thread in the Aluminium is the weakest part of the equation.
A clean lubricated thread will produce up to 25% more squeeze for the given
Lubricate the threads with oil. Grease is used to prevent rusting.e
#500 i have read all the comments and take
on board what was said. i think that putting oil on the threads is a
no no as it tends to send the torque settings haywire. as regaurds
the stud pulling out of the crankcase, this is possible and the cure
is 4 helicoils which are two and a half times stronger than a thread
tapped into alloy. the o rings are another must, and the later
breathing setup is another must if the engine is to become more oil
tight. also a one piece pushrod tunnel is a very good mod, one that i
would recomend. does anyone know the thickness and od of the washer
on the holding down stud, these were omitted when someone built the
motor. i thank everyone for the response. i was told by mr dodkin to
pull the head down to 24lbs, is this right ?.
#501 anyway i cleaned up the points and gapped them and checked out tappet
clearances and generally checked the bike over, primary adjustment,
etc etc. i cracked the bike bike up and went for a run. it was quite
tall geared with a close box and a 19 tooth gearbox sprocket. it went
like the wind and pulled 105 on a crono clock absolutly no problem. i
thought wow this is some motorcycle. i went out and about on it for
about a week and i was batting down a dual carrigeway doing about 80
when a fiesta xr2 passed me, i thought not having that and changed
down and followed, they hit just over the ton and slowed and i
thought lets get passed. i was just about to pass them when BANG a
noise like a shotgun then nothing, the motor just died. i costed to a
halt. i kicked the bike over and plenty of compression, i then
checked the spark, seemed ok, no noise when i kicked it over, i
thought werid. a couple of freinds pulled up and asked what was
wrong, i told them what had happened and they offered me a push. the
bike would fire but not start. invesigation showed that it had blown
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a condenser, i had the mag rebuilt and the bike ran fine. next job i
did was to take off the oil tank and wash it out. it was sparkling,
very clean. i put new oil in and went for a run, it ran great. a week
later i was out on the bike and it tried to sieze up, i came home on
tick over and stopped the bike and put it on its sidestand and oil
poured out of the chaincase. i thought whats going on. i looked into
the oil tank and there was no oil. i sratched my head. investigation
revelled that the tube in the oil filter was blocked with debri.
something at the time that i was unaware of. apparently if the bike
has had a atuomatic mag fitted at sometime in its life and stripped
the teeth, the remains go down into the motor and the oil pump will
pass it and it will lodge in the cross drilled hole. this is what i
had happened to mine and it cost me a set of main bearings because
after the event they whined like hell and they had to be changed. i
got the work done at criterion and they advised to leave out the tube
which i dulley did, and no probl
#503 The literature says 20lb./ft, remember aluminium expands more than steel. I
set mine to this and have no problems.
#509 i cant agree about oiling the threads, in a manual it
says torque settings and in brackets <dry> if it was to be lightly
oiled it would say lightly oiled, not dry. my mate went to an
engineering seminar and they got talking about torque settings, and
something that allways sticks in my mind was that the guy doing the
talk said, if you tighten a bolt to 40lbs dry and then add oil to get
to the 40lb dry torque with oil would be 5lbs. that has allways
stayed with me. when torque-ing a bolt or nut i allways check that
the thread has no tight spots. dirt or uncleanleness is not an
option. the problem that i have found is that adding oil makes the
bolt skid and it cant click off untill a much higher poundage is
added. i once tightened the rocker oil feed domed nuts on my rocket
three and forgot to clean out the threads with brake cleaner, what
happened was the tourque wrench wouldnt click off at 22lbs and it
pulled out the threads in the domed nut. and that was due to oil. i
am not mr perfect when building motors but sometimes things are
#512 Here's my nightmare, from yesterday, which began when I followed the
'red book' instructions for fitting the oil pump back into the
crankcase. "Heat up the case around the oil pump housing using a blow
torch." Heat up? How hot? The BMS manual talks about "considerable
heat". How considerable?
I broke a corner off the oil pump's cast iron base plate, by hitting it
off axis with a hardwood drift while trying to drive it back into the
housing. A Good Samaritan, an old-time Velo expert, took pity on me,
heated the case, withdrew the pump, cleaned up the abuse, replaced the
base plate and refitted the whole thing.
Now I know, having watched him, what considerable heat means. Blowtorch?
Propane gas flame? Forget it. He used a 'cool' oxy flame. Here's the
drill as I'd now write it.
Heat the crankcase until it will easily char-grill a thick fillet of
steak in thirty seconds. Continue heating until it is barely possible to
remain in the same room as the crankcase. When the sound of racing fire
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engines can be heard, and the jaws on the vice are starting to melt,
drive the oil pump into the housing. If it doesn't drop in with one
gentle tap, you need more heat.
Okay - wild exaggeration - but if the manuals had hinted at the very
considerable temperature needed, and given the hint that very little
force is needed to insert the pump when the temp. is correct, I might
have saved myself a lot of grief and my mate a lot of time.
#513 Gudgeon pin -Stock 86 bore pin is about 110g. The aftermarket pin in my VMT is 68g so a
lighter pin is certainly possible if you want to play around. As a guy who
seems to go through more pistons than socks, my experience is that lighter
isn't always smoother if balance factor isn't compensated. Question, maybe
for Dai, doesn't Burris's book say the balance factor was changed from 70% to
55% for the 86mm strokers? The ones I've checked were all 70 with a Hepolite
(450g or so).
Speaking of smoothness, I recently had an interesting experience. Throwing
my Venom engine together at the last minute before the rally, I finally got
in a test ride the day before the start and half way to Washington. Got it
hot and realized I didn't get the preload right on the mains and could wiggle
the crank when hot. Damn! The bike was noticably smooth though, smoother
than I'd ever recalled it being. Just rumbled a bit at idle.
I had all but given up on using it for the rally then suddenly came up with a
bodge extraordinaire. With it still hot I pulled the primary and drilled 3
holes in the case around the periphery of the outer race and tapped it in
with a punch. I was then able to slide a .002 feeler guage between the race
and the case, so it moved in about that far. I squirted some green loctite
in the gap, tapped the holes for 8-32 set screws to butt up aginst the race,
went to bed and prayed.
The bodge worked great but I noticed right away the engine felt rougher.
Paul D'O told me years ago that his tapered main Velos always felt rougher
when cold then smoothed out when the cases heated up. I wonder how much the
.004 spec pinch on the crank affects smoothness. I suspect I may have
preloaded my mains even more with the bodge. Also was told by longtime Velo
guy Dee that the tapered mains are very forgiving and I probably could have
just left it alone for the rally.
#514 however they do have problems and the one
that is number one in my book is the crank axle pulling through the
flywheel on the drive side. they have a taper but its not enough. i
mention this to other owners and i usually get the answer its years
old and if it was going to do it, it would have by now. my answer for
what its worth is never assume anything. my mate had his vm rebuilt
and i timed it up for him and it ran great, and sounded really sweet,
600 miles later he was out on a run and it devolped a bottom end
rumble, he asked what i thought, i had a quick listen and said that
is mains, he said it cant be its only just been done. i said i reckon
the crank axle has started to pull through, take off the primary and
have a look. he did and the end of the case had come off and there
was all the shims as well. you couldnt have cut it off neater in a
lathe. the problem is that having a spring under constant tension
acts as a puller and sooner or later it will come out. i had my motor
down and sure enough it was on the move. i had mine welded up but i
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have since learned that this is not really the way to go. the trouble
is that when you weld it, it tends to distort. the best way is to go
to nick payton in london my mate did and he machined the flywheel and
put in a flanged shaft and pinned it. game over as regaurds problems
in that area. i intend to have mine done that way as well. he also
made and machined a crankcase half and paired up the cases for what i
considered a very resonable price.
#515 I have a 1961 Velocette Venom Clubman 500. It starts fine when cold
but if it stalls it will not start up again when hot. I have recently
had my magneto (Lucas KF1) overhauled (about 2 months ago,) but it
still will not start when hot.
#516 same thing happened to me who ever did your magneto didn't do it
properly, I would ditch the whole thing and go electronic,
#517 I have a Thruxton which also will not start when hot. The magneto
was done by Dave Linslay and I am totally confident he did a great
job because it flys when I get it started, regardless of how hard I
ride it and how hot it gets. Before the mag. was reconditioned the
motor was inclined to missfire under load and was down on power.
When we had leaded fuel (oh no, not the unleaded fuel saga again!!)
available in Australia, I never had this problem of hot starting.
The odd thing now is that when the motor has been running and then
stopped, there is a white vapour which 'curls' out of the Concentric
MKII and if I open the throttle and get the inlet valve open (it's
easy to look down the carb throat on a Thruxton) until the white
vapour clears, it fires up readily - the same thing happens if I
remove the spark plug and kick it over a few times - it starts
easily. It is definitely not flooded and the NGK B8ES is dark brown
to black and not wet or fouled.
This may sound like I have been out in the sun too much but I can
assure everyone that this is always the case when the motor is hot.
#518 Wow, Paul Z you didn't mention THAT one on the ride! I have to say it's
brilliant clever, but I would have done it with the engine cold if I had the
nerve to do it at all, then you have a better idea of what the preload is
relative to the standard. How did you get a feeler gauge in there?
But on the subject of preload on taper roller mains, I think they are
indeed very forgiving. If you read the Bible of Bodges, ie the compendium of
tech articles, there are stories of everything from zero to 12 thou preload
on the taper rollers. The fellow using 12 thou reckoned his engine was
extremely smooth! Go figure. All I know is that when I set up my VMT mains
13 years or so ago, I went according to the book with no problems to report
so far.
And re cush drive taking out the drive side mainshaft, it's too bad the
factory didn't use the KTT style cush drive which sits on a taper and doesn't
pull on the shaft at all. All those years of hammering/pulling away on the
shaft can do it no good.
And re torque and oil on the threads; how on earth do they stay together
at all, knowing all the ways in which it's possible to get it wrong. Perhaps
ignorance is bliss after all..
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#522 I've had both of the problems mentioned here at different times in my Venom's
life. The drive side mainshaft pulled out of the flywheel not long after I'd
had the big end replaced by an engineering firm who I suspect didn't really
know what they were doing. This can be rectified permanently by pressing the
shaft back into position, making sure that the breather holes line up and are
clear, and fixing the shaft in position by a spot of weld or by pegging the
joint. So far mine has lasted over 20 years and is still going strong!
The broken drive side crankcase was a much more recent problem, occurring only
a couple of years ago. This time I sent the case to Seymour's who machined out
the damage and manufactured a new top hat bearing support in Dural which was
then screwed and Loctited into the case. This is apparently an old method of
strengthening the cases used by racers in the past, which is totally invisible
until you remove the engine sprocket or split the cases, and is very neat. One
of the great beauties of this method is that you continue to fit bearings in
exactly the same way as before, since the expansion rate of the repair and the
original material are to all intents and purposes identical. I've done quite a
few miles on the machine since and can honestly say that it's never run
#523 I can't remember where I learnt it from, but the answer to "How much do you
heat the crankcases to remove the oil pump or main bearing races" is an easy
one. You can use any reasonable heat source from plumber's blowlamp through to
an oxy-acetylene torch - nowadays I've found that a good electric hot air gun
works well with a little patience. Heat the case until spit sizzles off as soon
as it touches the metal and the pump or race will drop out or in perfectly.
I've used this method as a guide for many years and it's never failed yet. If
you don't get the cases up to this temperature you will really struggle to move
either component..
#525 Regarding heating crankcases, I wait for my wife to go out for the day and
use the kitchen oven when rebuilding an engine. The RHP catalogue says, “Do
not exceed 120 degrees C or the bearing hardness will be effected.” I have
found elsewhere that the maximum temperature is 160 degrees C. At this
temperature the bearings knock out when brought down sharply on a piece of
MDF and the pump slides out of the bore with a very gentle tap.
Ralph Seymour used soap turning brown when rubbed on an ali head to indicate
the right temperature for fitting valve guides.
#526 Try fitting a quarter or three eights inch heat insulating spacer between
the carb and head. Although I agree that just because a mag has been rebuilt
does not mean that it is working. This happened a few months ago to someone
in our VOC center, replacing the mag with a good old one cured the problem.
Additionally if you are running a NGK B8ES or equivalent spark plug with a
compression ratio of about 8 :1, try going down a grade to B7ES, this helped
in three cases I know of..
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#542 I have a 1950 MAC that recently underwent a complete nut-and-bolt
restoration by a very reputable builder. Although I have not asked
him directly, I assume this included a new or rebuilt oil pump as
well. On occasion, the crankcase floods with oil, presumably
involving some sort of problem with the return pump. This only occurs
after I have ridden very close to 22 miles (but again, does not occur
in every such case), which would seem to indicate a possible
mechanical distortion arising from thermal effects. The problem
appears to rectify itself when the machine is shut off and allowed to
rest for approximately 5 minutes. I have checked for obvious causes,
such as air leaks in the feed and return lines, or any obstructions in
the suction plug. There are no identifiable oil leaks from the
suction plug, the oil pump base, any of the feed or return lines, or
any of the fittings associated with the oil tank itself.
A knowledgeable individual opined that the pump is probably not as
prisitine as I would like to believe. In such a case, it would not
develop adequate suction to reestablish prime should it be lost (this
is plausible, since the last occurrence followed a long downhill
stretch at high RPM, which would presumably empty all of the oil from
the crankcase and the return side of the pump). Allowing the bike to
sit would cause enough oil to drain into the crankcase and reestablish
prime, which is also consistent with my observations.
#543 Do you mean the crankcase floods whilst the
engine is running ? If it does this you've certainly
got a problem with the oil pump (which should be able
to scavenge a greater volume of oil than it can
supply). I think I'd take it back immediately to your
highly-reputed restorer ! Presumably it didn't have
this problem before it was rebuilt ?
#553 . sparking plugs KLG FE70. Lodge HLN ChampionNA8 & Bosch W.175/T1
all seemed to be unlisted nowadays all the above are probably
unsuitable now days with unleaded fuel anyway, the plug in it is a
Bosch WW4DC that tends to carbon up a bit which suggests it's a bit
on the soft side. what do you guys recommend for a standard MAC
#554 NGK B6ES is the equivalent plug to the FE70
#581 I bought a 1951 MAC recently, because my brother in law has a 1952
one. Now we notice that his engine is about 2 inches "shorter" than
mine. What I mean is - the push-rod tube is shorter, i.e. no top
section, and the cylinder is shorter to match, with much more of the
rocker-cover visible than on my engine.
The engine runs fine, but I was wondering if this shorter engine is
a standard one, as we have never seen another and every picture
we've looked at has the same size as my 1951. (Picture of the
"short" engine is in the "pictures" section under "Keith Brettell."
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#585 my 1953mac is like yours, the rockerbox is right up under the tank
and it has a two sections to the pushrod tube but it is an alloy
engine and the first of the swinging arm frame macs
click on the club vellocette site & history scoll down to 1913 &
click the catalogue link scoll down to 1954 Click on mac.
#586 also click on 1949 catalogue mac on velocette club site
its a rigid frame one
#588 Just took a look at the short MAC. I've never seen one like that before. I
was thinking that maybe it might be a MAC/MOV hybrid as the MOV barrel was a
bit shorter than the MAC but I can't see it being 2 inches shorter. Maybe
its a short-stroke special?
#589 I certainly agree with your last paragraph, Tony. The bike runs
very well - it starts first time every time and runs well with
almost no mechanical noise, just a nice whirring of belts and chains.
I've only ridden if for a couple of hundred yards but that little
ride made me go out and buy one for myself. I think Keith is a
member of this group so perhaps he might chip in with a few comments
about how the bike behaves on longer rides.
#591 The "short engined MAC" is mine, for anyone who's interested I've
added a couple of close-up Pics on the Photos section in the Keith
Brettell Folder.
#618 Re Short MAC , In fishtail 184 Ivan Rhodes decribes how in 1973
he acquired a box of bits including an unusual short M type engine
fitted to an RE frame , He re-built it into a 53 MAC frame in 1980 to
be what the MOV might have become . He describes , engine number NOM
3184 , with short 6 fin barrel, NSU conrod , what appears to be a
Viper head ,53 MAC gearbox, light flywheels ,17/6 racing cam .
Maybe you have something similar inspired by the F/T piece.
#658 After coaxing the piston out of the cylinder (alright I jacked it out
using the barrel mounting studs!) I found that the piston rings were
well and truly stuck in the piston - by carbonised oil. One was
slightly loose at one end, and after a few weeks soaking in paraffin,
and the application of a blow lamp I managed to free it. The other
however refuses to budge at all, despite 2 months soaking in paraffin
(OK so 2 months vs the 50 years since it last ran might be a bit
optimistic!), and repeated attention with the blowlamp and some not
so gentle leverage on the end of the ring. The piston is aluminium,
I assume the rings (which I need to save as I doubt replacements are
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going to be that easy) are steel. Anybody got any pet remedies for
dissolving carbon deposits (without dissolving the piston)?
#665 i have a venom with alfin barrel.
I have adjusted the tappet clearance to .006 and .008 iaw the owners
On other classic bikes i have with aluminum barrel and iron liner the
clearance is adjusted to 0. You only verify that the pushrods can
easily be rotated by hand when engine is cold.
On my bike there is clatter from the tappets when the engine gets
I am considering to adjust the tappets as described above.
Will i have a problem
#667 You will probably burn out the exhaust valve and seat. You say there is
clatter from the tappets when the engine gets warm, usually tappet noise
reduces when the engine gets warm.
#668 Well it's easy enough to check your tappet clearnaces hot. On my alloy barrel
Velo the clearance typically increases .002" or so when hot (check your own
as I'm using aftermarket cylinder and studs). By the time I get the tank off
the cylinder head temp has dropped to 200F or so (400F during full flog) so
it's probably even a bit looser at times.
BTW, I quit using feeler guages to check clearances along time ago
(especially with one piece pushrods). Since one turn of the adjuster is
.038", it's an easy matter to turn the screw to zero lash (pushord won't
spin), then back off 1/6 or 1/4 turn to get .006 or .008. Not perfect but
works for me.
#669 My Venom was having the sulks and simply was showing no signs of life
on the kick starter.
So we tried a NGK Iridium IX spark plug type BR8EIX.
I interpret this to mean it is equivalent to a B8ES except it has a
resistor in the plug.
It was like throwing a switch, an immediate response from the bike
and it started on the second kick.
What is the experience with NGK Iridium IX spark plugs and Venom /
On the basis of this experince they may well be worth the price.
#670 1. What other new plugs did you use as a comparison, before opting for the
Iridium plug?
2. Are you running a mag or electronic ignition?
3. If you are running a mag, I thought I read somewhere that you shouldn't
use resistor plugs.
4. How many miles have you done since fitting the plug and does it still
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start perfectly?
Either way I hope it keeps going for you.
#671 My Venom has a recently reconditioned "standard" Lucas magneto.
I have been running NGK B8ES and recently NGK B7ES plugs.
I had been trying a softer Bosch W7CC that day, I've been using this
type of plug with some success in my Viper (it has a slappy piston,
burns some oil and runs on lead replacement petrol).
In terms of the Venom's recent starting behaviour, all plugs have
been the same.
Yes, I'm also puzzled about that resistor.
I'd appreciate feedback from others who may be running this NGK
Iridium IX BR8EIX type of plug.
#672 Sorry, but I just have to ask....what gap are you running? Perhaps
the iridium plug had less gap? Mags can use as little as 18 thou,
which definitely helps starting.
I've tried both platinum and iridium plugs in Velos and moderns with no real
advantage. They do seem to last a bit longer in the moderns.
Also, adding a bit of leaded racing fuel to my VMT's tank definitely improved
#673 VMT 260 has been running the same factory-spec KLG FE 220 for about
miles, with no problems starting or running. I've always used these plugs
the VMT, and there seems to be no problem with longevity or fouling, even
when the bore was clattering and the valves tockling away in loose guides.
Perhaps some plug trouble is experienced with the 'aperturus restrictus'
syndrome. Open those throttles wide once in a while; Velos can take a
#677 I know this is sacrilegious but a replacement Amal 390 for my Venom
Clubman II
came with a 200 main jet, and 270 is specified. Is there any reason why a
of careful work with jeweller's reamers couldn't open the jet? Ah, but who
risk his/her reputation and tell me the bore dia. of a 270?
#680 New jets cot approx. £2.50 in the UK don't risk it buy a new one (
you're not Scottish by any chance? )
#687has anybody gained experience aftermarket or self made camshafts for
ohv velos? I know that the original cams were quite good (50 years ago)
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but I think knowledge has improved a lot since then and I wonder if can
increase the performance of my venom with a cam of a more "modern"
#701 Has anyone got a Venom with Venom(Omega)piston and Viper-head?. I
have a -56 Venom endurance with .040 Omega Truxton piston and head
from Viper. I have opened up the combustion chamber to make room for
piston and calculated the CR to be 8.9. I`m going to fit one moore
decompression plate wich should lower the compression to 8,4.
Criterion said that I should use the MSS-flat crown piston with
machined Viper head but then the compression have to be too low I
think... What´s the point with Mss-piston? I don´t think that the 8.4
is too much or is it (we have 98-octane fuel here in Finland).
#707 You may want to look at articles on squishing in Fishtails 294 and
In the UK using 4* LRP with compression ratios above 8.0 will cause
The only other issue I can think of regarding the MSS piston is being
flatter is there will be less of an obstruction to flame travel (improved
flame travel is the main benefit of squishing). There is always a
to be made between increasing the CR and obtaining the best combustion
chamber shape.
#708 A friend who wants to build up a 1959 MSS from a pile of parts has two
of flywheels. The dia/thickness of one pair is 209mm/20mm and the other is
196mm/18mm. Is the smaller pair from a Viper maybe? Is the larger pair
correct for an MSS?
#714 Technically they are both for the MSS (or Viper for that matter).
changed the dimensions of the flywheels to reduce oil drag as the larger
are a very tight fit in the crank cases. This took place in approximately
1958. Additionally the smaller flywheels give the main bearing housing an
easier time, particularly if your MSS has the small bearing housing. The
with the heavy crank is supposed to be a super bike to ride due to the
heavier flywheels and softer cam, so the choice is up to you,(although
Veloce must have had a good reason for reducing the flywheel size).
Just one check, I am assuming you are talking about a spring frame MSS
engine number 10001 onwards, as the iron MSS also has the larger flywheels
with a 96mm crank and bolt up big end. I am about to build a spare engine
for my 1937 MSS sprinter, and cannot make up my mind whether or not to turn
down the flywheels to the smaller size or leave them as is to benefit from
the greater flywheel effect off the line. Is there anyone who has any
experience of this?
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#720 For the fellow who mentioned using a Thruxton piston with a Viper
head, this
would be a mistake. The reason Viper heads are used on 500s was to take
advantage of the smaller chamber size, use a flatter piston dome (MSS) to
flame travel and incorporate some squish area as well. Opening the Viper
out to take the high dome Thruxton (same as Venom) piston would negate
advantages. My squish head bike runs 10.5:1 compression on 92 octane
unleaded with only 28 degress total advance.
Flywheels size: I had the large MSS wheels in my 86mm stroke Venom for
and finally put the smaller wheels back in this year. About the only
advantage I could notice was it's a bit easier getting the clutch out
a stop sign with the larger wheels. Once under way, first gear
is better with the light wheels. My other swingarm Velo has 96mm stroke. I
had occasion to do the big end a couple years ago and while I had the
split I carved them down to the smaller size as well, removing four pounds
metal in the process. Same result as the Venom, quicker in first gear. I
don't believe the large flywheels aid vibration much. Given the same
factor, the only benefit the larger wheels have is smoothing out the power
pulses, and in the case of a Velo the size of flywheel compared to the
pulse is enormous.
#726 (from Finland) Bloody hell, so I ruined the Viper head because I made
the combustion
chamber to full hemispherical shape... So is it now same side as Venoms
combustion chamber or is the Venoms chamber more deeper than Vipers? So
you use unmodified Viper head and MSS-piston or what? Because
Criterion-people said that you must machine the edges of combustion
chamber to match cylinder bore edges, but then it is the same shape as
Venoms I believe or is it? If I now put MSS-piston I don`t have
compression at all..
#732 I'm afraid by cutting the Viper chamber out to fit the Venom piston
all you
have now is a Venom head with smaller valves and ports (which some would
argue is not all bad). The chambers are the same depth. I believe the
general way it's done is to machine the Viper chamber just enough for the
piston to clear around the circumference by whatever you desire for squish
band, in my case .035. I am not one who believes a 500 can run up top with
the small Viper intake port and valve, so I have a Venom head with the
welded in for a 'bathtup' chamber.
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#734 Thanks Paul for good information. So I ruined a perfectly good Viper
head, great job. I just understood wrong the method to convert the head.
In my case the bike came with just bored cylinder and new Omega Venom
piston but without original head. With the bike came a Viper head wich
naturally don`t fit with Venom piston so I went on and opened up the
chamber so I can use the new Omega piston. The head has bored out (to
30mm) intake port but smaller valve. I have also a new Venom intake
valve. So if I change the seat and valve do I then have basically a
standard Venom head? And is this job to be trusted to normal automotive
workshop or is there danger that the seat can drop when engine heats up?
I heard that the head must be heated up before installing a new seat.
Otherwise the head is in very good condition...The bathtub-welding
sounds interesting, I saw the same in Commando-head with D-shaped
exhausts ports and that was very effective indeed. Is your welder
interested doing any moore these heads to some foreigner abroad
P.S. How can you use such a high compression ratio (over 10) because in
previous messages some said that over 8 cr causes pinging at least with
english petrol? Is that squish band so effective that you can use higher
compression ratio?
#735 At this point in your shoes since you have a new piston, matching
fresh bore
and a new valve I would put in the Venom intake valve, shim the cylinder
whatever compression ratio guys who burn your petrol get away with and call
it a day. Nothing wrong with a good running Venom spec engine. I probably
have twice the horsepower of PdO's Velos and he still passes me. I think he
leaves his brake levers at home.
If you are interested in high speed hunting down of Norton Commandos or
modern machinery (one of my favorite passtimes) you can get more umph but
you'll need to work up to a Thruxton size carb and intake. I have a Venom
head ported out to 34mm with no welding (go up with the port, don't lower
floor) and it works well with 36mm carb.
I think the factory claimed 5hp increase with the few Thruxton squish head
engines they built, sounds a bit much to me. The squish is good for about 1
point increase in compression ratio in my experience. You could run twin
plug (I do in both my squish and non-squish Velos) and get some of the
benefit of squish that way but don't expect more than a hp or two. I run 35
degree advance instead of 38 in the non-squish motor with twin plug. Can't
do it with a mag though. If you do twin plug, put a 10mm plug in
you can get it out on the same side of the bike and without taking the tank
off. More details on how to if needed.
Valve timing, particularly the point at which the intake valve closes
the compression stroke, has everything to do with effective compression
ratio. Just last week I changed cams in the Turd ('59 Venom). With the /8
cam I had in it, the intake valve was closing late (I couldn't use factory
timing, valve hitting piston), the engine was sluggish in the mid range but
not a hint of detonation. I replaced with a /5 cam (I have high ratio
arms for .5 inch lift so don't really need all the duration of /8 cam in a
500cc) to close the intake valve about 10 degrees earlier on the
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stroke. Mid range power went way up, no loss on top however a bit of
now due to the increase in effective compression ratio. When degreeing in
your Velo cam, the spec you are most interested in is the closing of the
intake valve, it is by far the most important of the four valve events.
I have trusted automotive machine shops that have experience with VW or
air cooled engines with Velo seats, so far no failures.
#745 My Viper thruxton 500cc is fitted with a 32 mm concentric, is this a
good choice. Im finding that there is a spitting back in the carb
(really it is a small flame inside the carb at idle or just above
idle)......what causes this? Should I fit the GP5 carb? I do have the
correct manifold on. I have also noticed that there is a flooding of
fuel into the head is this just a bad float needle or a bad angle for
this particular carb?
Also on another VMT i blew a hole in the piston I did read about
another soul who had the same problem ...Should I strip the engine to
find the bits in the oilways etc.....what is the main cause of this
in there a filter of any kind that can prevent the oil
pump from getting seems that it was an Italian piston
is this a possible
#746 Spitting back in the carb can be a sign of a weak mixture, although
you do say that there is flooding which would perhaps indicate enough
fuel is getting through (unless there is a restriction in the pilot
jet leading to weakness at tickover, and the main jet / needle is
oversize leading to flooding when the throttle is opened ?. I would
think that by checking the state of your plug immediatley after a run
i.e. not letting it tickover before you check it, would indicate
whether or not it's running rich? What is the engines performance
like when it's running above tickover?
A friend of mine blew the piston in his venom earlier this year.
Although he had only owned the bike for a short period it had been
running fine prior to the problem. He checked the ignition timing and
that was ok. The only thing he could attribute the problem to was
that he had replaced his petrol tap and when he examined it he found
that the flow of petrol through the tap was restricted. This may have
caused a weakend mixture leading to overheating. He took the safe
option and completley stripped the engine to remove the bits of his
piston - it would be a pity to rebuild the top end only to have
engine failure due to restricted oilways or a pump problem. There is
a suction filter plug in the bottom of the crankcase that stops
debris from reaching the pump, but I'm not sure how effective this
would be in stopping fine bits of alloy, from the holed piston,
reaching the pump? The Velo owners club do quite a nice conversion
kit that replaces the fabric oil return filter in the oil tank with a
more efficient cartridge type filter. The kit also allows return oil
to bypass the filter if it becomes clogged. However, this is on the
return side the oil having already retruned through the scavege side
of the pump which would not help in this case.
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I would also be interested in any body elses comments regarding holes
in pistons.(see also msgs #908 etc under ‘Fuel,Oil’ heading)
#747 If you've melted metal in your engine, doesn't it sound like a good
idea to
clean it thoroughly before you run it again? I know someone who's on this
list who didn't strip after a piston became a breather pump, and he sheared
his oil pump shortly after rebuild, seizing piston #2! As aluminum isn't
magnetic, it's really hard to drag the little bits out. At the very least,
take the engine out and flush everything very thoroughly, and blow it out
with compressed air. You just might get away without taking the cases
Petrol vapor/spitback is a function of valve timing, and is normal at low
rpm's with an M17/8 cam and Thruxton followers. It's part of the compromise
for high rpm performance.
#748 While I haven't holed a piston, I did buy an engine with a holed
piston. On
striping the engine I found "blobs" of ali in the crankcase, which had
wedged between the crank and cases. Aluminium was crushed in the main
bearings. It also lodged aluminium in the pump which seized the pump,
striping the oil pump drive worm and cracking the pump housing. The oil
requited stripping to clean out all the contamination.
#749 I was led a merry dance by a carb spitting problem at kickstart/low
The culprit turned out to be the ( peripheral ) slip ring in my manual BTH
magneto; there was a section missing! Presumably, at higher revs the points
operating arm jumped the gap.
#752 The Plug was black and the engine runs very well past the tickover
speed. The
tickover passage in the carb was cleaned out thoroughly. In general should
VMT have a compression plate added to reduce the chance of a holed piston?
#753 My Venom runs an optimised 8.75:1 compression ratio (measure the
volumes to
make sure), the same as a Thruxton. Cams are M17/8 but with standard Venom
followers, head and valves. Carb is a 30mm Concentric Mk1 with a 3" long
velocity stack (proper Amal turned type, with a blended venturi). Getting
carburation exactly right was a bit of a pain, but it now runs quite
happily at
all speeds and loads, with no more pinking than I would expect on a Velo (I
believe that they can stand more than people realise). I run on either
unleaded or Optimax (not yet sure if there is any advantage to Optimax due
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my experiments with carburation overlapping with the introduction of this
to the marketplace), in either case Nominal RON value of 97/98. I always
that the motor ran more happily on unleaded than on LRP. I have never holed
piston or got anywhere close, and I'm not known for treating the machine
The main reasons for holed pistons are weak mixture, over advanced ignition
timing or low grade fuel, all of which I would expect to produce an
amount of audible detonation (pinking) long before any damage occurred.
However, if an engine is run at certain speed/load conditions where it is
to the pre-ignition limit, coupled with any or all of these factors,
will be extremely rapid.
One other possible cause could be the use of a spark plug of the wrong
(too hot or soft), creating a hot spot in the combustion chamber. Couple
again with any of the factors above and the same disastrous consequences
#756 Just finished a rebuild on VMT457 and discovered a trap with recycling
gaskets. It can be done - just anneal the old one and put it back in. Up to
the point where it has become too thin, that is.
After tracing a misleadingly metallic chirping noise to puffing around the
joint, we lifted the head and measured the thickness of the old gasket :0.025". We then rifled through the parts bin and found a motley collection
new and used gaskets, some a good fit in the head, others loose and thus
to sit off centre and protrude into the combustion space (and in one case I
heard of, protruded so far as to actually catch on the edge of the inlet
valve!). Chose a reasonable one and measured it:- 0.045". Annealed it,
the plot back together and problem solved.
#757 Always liked this site on the Concentric
Frank Forster came up with (wrote?) a lengthy article on this carb, perhaps
someone on the list could forward it? It would be a good one to have on the
egroup files.
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#762 Just fitted a 1036 Concentric recently, the air correction orifice
center of the 3 holes) needed to be opened from .080 to about .135. Make
sure you have the 4 stroke siphon tube, the one that is cut flat across the
thanks for the info . Can you tell me why the air correction orifice has
to be opened and how? Also what is the 4 stroke siphon tube?
#770 The air correction orifice performs the same function as the air
lever on a GP, it allows some air to enter in the mix at the siphon tube,
brass tube that needle enters into first. Two strokes need lots of fuel at
low rpm so the air correction is small and the siphon tube is usually slash
cut across the top, four strokes are flat cut. To convert to four stroke
take the siphon tube (along with the needle, needle jet and jet holder,
different, and whatever main you want to start with) out of most any
four stroke Concentric. While you have the siphon tube out of the 1036,
match the size of the air correction hole (the center of the three that
to the siphon tube area) to the four stroke carb you just cannibalized from
about .080 to .125-.140 I believe, or you can see how it runs and gradually
open up the hole. You will probably need a 3 or so cutaway on the slide,
can file it if it's a 2.
#771 What is the size of the standard Viper inlet valve head diameter?
#772 My information says, Inlet 1.69 inches, exhaust 1.56 inches - but I
checked Viper valves physically
#775 So the exhaust valve is the same in all venoms and
vipers but the vipers inlet valve is smaller (and of course thruxton has
2" inlet valve I believe...). Is there a significant loss of power if I
use a Viper head with 30mm intake port and small intake valve in Venom
(combustion chamber is shaped to match Venom)?
#776 Nowp - Viper exhaust is smaller. check in the engine section here
I have an engine simulation program, which I have just checked for a Venom
with Viper valves. While I cannot claim it's accuracy (vendors claim less
than 5%) it shows approximately a one BHP reduction in peak output, and a
similar amount of torque reduction (ft - lb)
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#790 I am also trying to source an air filter for same.
#791 Grove Classic Motorcycles on +44 (0) 1582 873066, e mail [email protected] has
loads of original air filters at a reasonable cost.
#819 Accessory Mart has KLG FE 220 plugs, standard fitment on Thruxtons, on
at $1.80 ea. currently. They are at 513 871 6682, in Ohio. Part # 06-00384.
I've had the same plug in my Thruxton for three years, and it starts
first kick.
#850 At 38 degees btdc what is the exact imperial measurement that a Venom
piston is from the top of it's stroke. I will use this to time the
engine with a dial-guage.
#851 A word of advice: use a degree disk, this will be considerably more
than using a dial gauge and does not necessitate the removal of the head to
the job. If you use a positive stop method to find TDC this is the most
accurate method of timing. My positive stop is a spark plug body with the
insulator carefully removed - just run a fine hacksaw cut around the
above the hex and the insulator will drop out - run a 10mm tap through
removing the earth electrode and fit a 10mm allen bolt or similar with the
suitably rounded to prevent damage to the piston and long enough to stop
piston before it reaches the top of its stroke. By rotating the crank back
forth to the stop (slowly and carefully), TDC can be found by splitting the
difference between the readings. The result is an exact TDC setting which
no compensation for backlash.
#852 From 36 to 38 degrees the piston drops 20 thou per degree, so this is
a more consistently accurate method of setting timing than messing
about with degree wheels. And certainly more convenient, you can
even do it by the roadside. But the measurement is taken along the
bore centerline, so a dial indicator that screws into the spark plug
hole will not yield accurate measurements, due to its angle and the
probablility that the point will move on the piston as it drops. Use
a small steel rule, this will give more than adequate accuracy.
So here are the numbers - 36 degrees is 0.3957" BTDC and 38 is
0.4384". Keep the rule vertical as you measure. I use 0.040" and
0.4375" (7/16"). I marked an old spoke with a file and keep it in the
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#855 Back of an envelope and IE6 calculator stuff (scratch scratch)
Venom stroke is 86 mm, right? (not sure - I am an LE man)
reckon piston rise = (86/2)-(cos 38 x (86/2))
43 - (0.788 * 43)
43 - 33.884
9.116 mm
0.359" or 23/64" in Imperial.
You did ask for "exact" and my IE6 calculator works to 33 decimal places,
#856 I have an alternator on the end of the crank and have it degreed so I
use a
strobe light. And I always find no matter how carefully I set the timing
statically, it's always a few degrees off when running, presumably due to
gear lash, bearing float etc.
That said, a few degrees off, unless over advanced to detonation, is hard
me to notice in the seat of the pants. Could make for a hot piston though,
and we all know what happens next
#861 After a recent engine rebuild I established TDC with the positive stop
throught the plug hole/degree plate system, then tried two others, purely
out of interest. A sensitive dial guage, anchored on a rocker cover bolt,
thrugh the plug hole, got me within one degree every time (read off the
degree plate, still in place). Slightly more accurate (here comes the
heresy) was a fine pointed scriber inserted through the plug hole and held
against the piston top with the fingers pressed
tightly against the plug cavity. Rocking the piston back and forth either
side of TDC, then judging the moment of no movement consistently found TDC
+/- less than one degree.
#862 Can someone tell me the length of the Venom conrod please?
#864 According to the technical site, the rod length is 6.875" centre to
#866 I think the equation is
d = S/2 + L -S/2 cosX - L sin {cos (power -1)(S/2L sin X)}
equals distance before TDC
length of connecting rod
angle before TDC in degrees
You can still ask your granddaughter to work it out though, as I haven't
used log tables since I was forced to give up engineering 24 years ago!
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By the way, for those of you that don't want to drill / chisel out the
centre of a spark plug, Seymour's sell the correct graduated tool for the
job at about GBP5
#868 if you're stuck on the road re-time
the mag to open the points at TDC on full retard. Its good enough to get
#869 38° BTDC is the correct timing for the old leaded fuel.
36° is more likely to work with standard leaded fuel without preignition.
#871 right boys, this is how it is. i have tried a few different methods
and i have heard about the positive stop method, but for me, i find
that i need to go through my own method. firstly remove the gas tank.
then remove the dynamo outer cover and pull out the splitt pin out of
the crankshaft. then unscrew the dynamo pully off the crank. then
slacken the dynamo strap and undo bottom mounting for inner dynamo
cover. pull the inner cover forward and turn clockwise to about 20 to
the hour. then push it back and tighten the dynamo strap. this now
puts the inner cover out of the way and gives accsess to the crank.
next, get a thin piece of wire and slacken one of the primary screws
and make the letter u at the end and put it under the screw and refit
it and tighten it up. bend the wire so that when the degree plate is
on you will have a pointer. you will need a timing disc, a plastic
one is fine. make sure that the hole of the disc is compaterble to
the crank. now, you will need two big penny washers, they need to be
not too thick and have a hole compaterble with the crank. now, take
the castleated nut off the two dynamo discs and sandwich the disc
between the penny washers and put on the crank. then put on the
castleated nut and tighten up. this serves two purposes. one. it
makes the degree disc strong and flat, and two, you can now kick the
bike over. next remove the spark plug and now you will need a dial
gauge. a draper one works well. now you will need to find the
compression stroke. put your finger over the hole and turn the motor
over untill it starts to hiss. you are now on the compression stroke.
bring the piston up to the top of its stroke and then slacken the
casleated nut and set the degree disc to twelve oclock. i.e. zero at
twelve. now the trick is to find an accurate tdc. with the piston at
the top of its stroke, screw in the adaptor for the dial gauge and
then insert the dial gauge. you may need to screw an extention on it.
let the dial gauge down until it just kisses the piston. this is
important. now what i do next is to get a trolley jack and put it
under the frame on the l/h side where the mainstand would be, as i
dont have a mainstand. i then lift the bike so the backwheel is off
the ground. put the bike into first gear and now you can operate the
crank via the back wheel. if you have a mainstand fitted that should
work good as well. turn the rear wheel clockwise to turn the motor
backwards to take itt off tdc. now bring up the piston up to tdc
again and watch the dial gauge needle and slow down as the piston
contacts it. <when the piston kisses the dial gauge it should just
blip the needle.>set the gauge to zero by turning the outer on the
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gauge, as the needle starts to lift, keep zero-ing the needle. this
has to be done very slowly as it blips the needle qiuckly. when the
needle starts to drop, stop and bend the pointer back to zero on the
degree plate.look straight at the degree plate as looking at it to on
side will give a slightly different reading. now, your dial gauge is
showing the piston starting to drop away after the rock on the crank
at tdc. turn the rearwheel anti clockwise very slowly and watch for
the needle stating to move again, when it does stop, and look at the
degree plate. check the amount of degrees of movement and split this
in two and that is tdc set very accuratly. turn the motor back off
tdc by turning the rear wheel backwards to past 40 degrees. then
bring it to 40 degrees and set the points to just breaking, a
cigarette paper is spot on for this. make sure that you have pre set
your points gap. get your paper between the points until it will just
pull out but there is still a little resistance. i find the next step
is to have two people to do the job, as with one it is just about
impossible. have one person hold the points in the mag with his hand
as it is breaking at the points and have the other person put the
magwheel on the otherside and tap it smartly with a deep socket and a
hammer to put it on to the taper. i gaurentee that if you set the
degree plate to 38, you will end up with 36. been there, done that.
when set at 40 you will get 38 when it is rechecked dont ask me why,
but i allways get 2 degrees of movement. the motor is now set at an
accurate 38 degrees. super unleaded is a highish octane and with
silkolene pro-boost added with it you wont get detonation provided
that the motor is not running too lean of course. i hope somebody can
use this info. regaurding setting the timing at the roadside, i have
never had to do it as i make sure that nothing will slip when doing
assembly. if the magwheel is foregin to the magneto shaft, lap it on
to the shaft and when it is pulled up it will never slip. remember
that when assembling, that doing it wrong ends up in faiure sooner
rather than later. if the mag fails when you are on the road get the
yellow taxi home.
#874 I use a stiff metal
degree wheel, drilled out to just slip over the threaded part of the drive
side mainshaft. Then I replace the nut which holds the generator pulley
(after removing the shock-absorber spring and pulley), tightening it onto
disc, which abuts the slotted part of the mainshaft. I then turn the crank
with a wrench on my timing side mainshaft (Thruxton - I check the valve
clearances at the same time), using the positive stop method to find TDC,
remembering to move the crank 30 degrees or so when trying (again!) to get
all right, in order to accommodate any backlash in the timing gears. By the
way, I time at 38 degrees, and have had no problems with pinking or melted
#883 I was out on the MAC (1951) the other day when the engine unusually
when I closed the throttle at a junction. It started again first kick and I
carried on. It did the same thing again a minute or so later. Again, it
started OK but this time I noticed it wasn't pulling so well. After a short
time the engine started to run very rough and then just stopped. I pushed
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- not very far, fortunately.
Now, the engine is firing early, during the compression stroke I think, and
pushing the kickstart back up against my foot. I also get an oily-smelling
blowback through the carb.
I know it's a timing problem, but haven't had to deal with this before so I
wondering if anyone could advise me on what probably went wrong so I know
to start.
#884 it sounds like you have stripped the fibre gear wheel on the magneto.
when you take off the timing cover, and if this is the case, remember
to flush out the lower end of the motor to get rid of all the bits of
fibre teeth. i belive there is a firm that now make replacement auto
advance units in alloy.
#892 I had the same problem once, & suggest you check your
mag timing gear which is probably fibre & may have
stripped a tooth.
#888 Another word of advice - DO NOT use an alloy replacement for the fibre
These will wear quite badly and deposit alloy shards in the sump, which
will do
rather more damage in the long term than the bits of fibre. If you are
going to
replace with anything then use a steel gear. Reference to previous postings
will provide the details of the man who can!
#889 I'm a fan of the John Hales modified ATD's, superb,
and in my MSS.
Those nice prople at Criterion have been supplying very good
adjustable ALLOY pinions for years ( NOT for ATD's ) and I've
never had any problem with shards filling up the engine.
#890 I used an alloy replacement pinion on my ATD after the fibre one did
disintegrating thing many years ago, and when I stripped the machine quite
few years but not so many miles later the pinion was showing signs of quite
severe wear and there was a fair amount of alloy around, mostly little bits
all about the length equivalent to the width of the timing gear - it didn't
take much deduction to see where it had all come from! I replaced the
again about two years ago with one of John Hales' steel gears and so far so
good, no sign of wear at the last inspection when I had the oil pump
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earlier this year.
#891 I have formed a golf ball sized piece of Bluetac (plasticine) around a
nail, then pressed/screwed it into the plug hole far enough to achieve a
tight seal. With the nail withdrawn, a depression formed around the top of
the resulting hole and a drop of washing up liquid in the depression,
bringing the piston towards TDC results in a growing bubble. As TDC is
passed the size of the bubble diminishes. The bubble is very sensitive to
small movements.
#896 A very novel idea!
this cannot fully account for the
backlash caused by running clearances at the big and small ends and piston
due to both the taper of the piston and the piston to bore clearance. The
method that will accurately find TDC irrespective of these factors is the
positive stop method. It will however, still be necessary to account for
backlash when setting the ignition timing by only ever turning the engine
FORWARDS to the timing point so the backlask in the timing gears is taken
#897 i still reckon that by using a dial gauge and a degree
plate you will get as near as you can get to get an accurate tdc. to
allow for slack in the small and big ends, i can see where you are
comming from, but when you use the dti like i do, you can work to a
miniscule fraction which has to be more accurate than the positive
stop method. as for timing back lash, velos have fine helical cut
gears and any backlash can only be minimal compared to a triumph or
bsa which have corse cut straight gears. i was allways told to take
the timing past 38 degrees and then bring it back to take up any
lash. without question you have to time at 40 degrees to get 38. i
have tried forever at 38 and when rechecked it is 36. beats me why
but it is.
#898 At the end of the day, if you have found a method of timing which
gives good
repeatable results then stick with it. The Velo will never be as critical
regards ignition timing as a modern racing two-stroke, so this argument is
largely academic!
#901 what is the positive stop method?
#905 Michael (and anyone else who might be in the dark about the positive
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This is a method of setting up the degree disk accurately prior to setting
checking ignition or valve timing.
First obtain a suitable degree disk, these are available from most good
part suppliers or classic bike part dealers. You will also require a piston
stopper tool, these are available commercially although may be harder to
find I have made mine by modifying old spark plug bodies, since I regularly work
a variety of engines I've made a set of three to suit engines with 10, 12
14mm plugs. These are made quite simply by running a hacksaw cut around the
steel body where it is crimped over just above the hex and withdrawing the
porcelain insulator complete. Cut off the outer electrode and run a
sized tap down through the hole. I found that 6, 8 and 10mm threads
respectively worked well. Take an Allen cap head bolt of a length which
run through the plug body and protrude about 25 - 30mm through into the
combustion chamber and round off the end so as not to cause damage to the
piston. You could also file a flat on one side of the bolt to allow air to
escape as you turn the engine over. Screw the bolt into the plug body and
Loctite in place.
Remove the dynamo pulley and shock absorber spring and fit the degree disk
to the end of the crankshaft using the pulley nut finger tight for the
to retain the disk. Fashion a pointer from either a piece of sheet metal or
stiff wire - I use 16G welding wire bent in such a way that it can be
on the sprocket cover mounting studs and triangulates up to the edge of the
disk and doesn't move unless I want it to but any suitably solid mounting
will do. Remove the timing cover and with the spark plug removed, turn the
engine over with a ring spanner or socket on the timing side crankshaft nut
until the piston is roughly at the top of the stroke - at this point you
be able to feel for the piston with a small screwdriver inserted in the
hole. It doesn't matter which stroke you are on at this time, the stopper
not foul the valves. Loosen the pulley nut and turn the disk on the shaft
the zero mark lines up approximately with the pointer and tighten the nut
finger tight once again. Turn the crank back or forward, it doesn't matter
which way, by about 90° and fit the piston stopper tool to about 10 ft-lb
torque. With your spanner, turn the engine over either way slowly until the
piston stops against the tool and hold it tight in this position while
the reading on the disk. Turn the engine over the opposite direction until
piston once again stops against the tool and take another reading. You will
have two readings which should be fairly close to each other, e.g. 35° on
side and 45° on the other. By splitting the difference you should now reset
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disk or pointer to read in this example 40°. If you now recheck by turning
engine back to the other stop, you should have the same reading, i.e. 40°
the other side of zero. Now remove the stopper tool and by turning the
until the pointer is on zero you will have true TDC.
Now you are ready to start your timing checks.
Ignition should be set at 38° BTDC fully advanced for 98 RON or better
fuel. I
would say that if you can only get 89 - 92 RON then this could well be the
cause of holed pistons and audible detonation (pinking) would be horrendous
with 38° timing. If this is the only fuel you can get I would strongly
to retard the timing by a significant amount. You could try 34° and see how
goes - retarded ignition timing will cause the exhaust temperature to rise
consequent blueing of the exhaust downpipe is probable together with a loss
performance but this may be inevitable if you want to prevent engine
Ideally you should try to find higher octane fuel, in the UK our premium
unleaded is 95 RON which I consider too low for the Velo. Super is rated 97
RON, but pump average is in the region of 98 - 99 depending on supplier. I
don't believe that unleaded fuel will do the engine any harm.
#906 on an old banger such as the Velo - no
disrespect intended - accuracy to this degree is unnecessary. Having said
I prefer to use a good old fashioned Rizla Blue cigarette paper between the
#910 One more question pops to mind. How many degrees of change does the
manual\retard advance lever make? Can it solely be used to retard the
from say 38 to 36 degrees with any kind of practicality?
#914 Sorry I can't answer this - perhaps someone with a manual mag might
But while it is possible to back off the ignition slightly with the lever,
of the time you would want to run fully advanced simply for ease of riding
- at
normal engine running speeds even an ATD will be at full advance - the ATD
the manual lever are only an aid to starting really. To trust that you did
over advance the lever I would suggest to be a bit risky. However, you
use the lever as a test, gradually increasing the amount of advance until
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identify the point at which excessive pinking occurs, leave the lever at
point and check the timing to establish the exact figure. Ideally this
would be
done on a dyno by running spark sweeps over a range of throttle openings to
establish the MBT (Minimum spark for Best Torque) and BDL (Borderline
Detonation Limit) curves, to give the technical terms, but more practically
the average enthusiast, a good degree of patience and feel coupled with a
of trial and error will get there in the end!
#917 The magneto, if set up correctly, will produce its best spark only at
full =
advance, but I doubt if 2° will affect it significantly. The problem would
e to move the lever only enough to give you 2° retardation.
#923 I checked this a few months ago on my MSS sprinter and from memory the
manual mag control allowed a variation of between 4 to 38 degrees.
Originally I marked every degree as I wanted to try to check what advance
gave the most power. I gave up on that idea as the greatest variable was
consistency with which I coordinated the clutch and the throttle.
#935 Is there an alternative to the NJK
plug; what is the best plug for the totally standard Thruxton running on
poorer octane unleaded gas.
#939 I run an NGK B8ES. The equivalent Champion is N3 but I found NGKs a
lot more
reliable. Either should be OK or you could try a B9ES if you ride
#944 In reference to the query on what plug to run in a Thruxton; I run KLG
available from Accessory Mart for $1.80 ea; this is what Veloce
#948 But really, if you are running a road bike
there should be no need to go down this route. Just use the highest rated
fuel available in your region and adjust ignition timing and perhaps
carburetion to suit.
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#952 Are Mk 1 KTT flywheels common to any other model (ie. Mac)?
#953 Was the barrell standard KSS for this first
year? (1929 Mk.1 KTT)
#954 The barrel in 1929 is the same as the KSS
#955 Mk I flywheels. These are basically the same items used on Mk I
K models from about 1931 up to the Mk VIII. The size of the crankpin
changes in
this period and earlier versions can be modified. The main thing is that
wheels are steel in place of cast iron as used on the earlier K type motor.
The mainshafts are the same of course on all the above motors with the
drive side shaft.
The MAC wheels are similar but different. You may be better off starting
scratch and machining up new wheels and shafts, the drawings are available.
#956 It's a long time since I rode a Velo but I seem to remember my best
were with a Lodge FE 80 or some such thing, Champions were the worst
#957 Interestingly three of us have been experimenting this summer with
softer plugs in our Venoms. Two of us have moved down to B7ES, giving
noticeably improved starting, and one has even gone down to B6ES. Probably
most of our rides are only 50 or 60 miles, albeit pushing close to the
maximum speeds (!), no holed pistons to report yet.
#958 There are as many spark plug preferences as there are plugs. I suggest
reading the spark plug article in Dai's website (and just about everywhere
else one looks) by the late Gordon Jennings. This is widely recognized as
the bible for engine tuning via the spark plug.
After reading, take his advice and get a projected nose plug for your Velo.
I run NGK BP7ES. You will have the benefit of a hotter plug for starting
and idling, plus a cooler plug at speed when the incoming air charge
(especially with the Velos hemi head) will cool the plug. I noticed the
improvement in low speed operation immediately in my Thruxton.
timing may be able to be retarded a degree or two with the faster burn
the spark occur further into the chamber.
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Don't worry about piston clearance, I have run them at 10.5:1 compression.
#964 I have freshly bored Venom with Omega piston. Piston rings are
those "black" ones. Is it better to change these to chrome rings and
three piece oil ring? And can you get those rings anywhere to suit
#965 Standard Velo-sized rings should fit the Omega piston. Modern oils
prefer a three-piece oil control ring.
IMHO, the best rings are made by Total Seal, they include a chromed
top ring, two-piece "gapless" second ring, and three-piece oil ring.
Your "black" rings are plain cast iron. Total Seal has a website
( and dealers in many countries. Their HQ and
manufacturing facilities are in Arizona, the phone number is 800 874
2753. They should be able to give you appropriate part numbers, or
even sell directly.
#975 . Any experience with what a resistance
plug will do to a BTH, or a Lucas mag? I understand
that a wider plug gap puts an increased load on any
magneto, but I don't know of any correlating
information on air gaps vs internal resistance of a
high tension system.
#976 I have a Viper head in my venom and I´m thinking of changing the
valves to the bigger ones of venom. Now I`m wondering if there is
enough room for the bigger valves to operate. The combustion chamber
is machined to same size as venom`s. So is there a danger of valves
to clash or is the valve geometry and location same in Viper and
#977 My 1959 Venom exhibits poor hot starting. I'm fairly new at Velocette
set up (I had my last one about a third of a centuary ago). Cold it
starts almost first kick. When hot it is very unreliable. I am using
a Champion N8 plug.
Is it set up or starting technique?
When I remove the plug after a non starting episode it can be wet,
sooty and hot. There is a good bluish spark.
Ideas anyone?
#983 In almost all cases of this sort, the magneto capacitor and/or coil is
responsible. They degrade with heat.
What model magneto do you have? The Lucas are more susceptible to this
malady than BTH.
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#985 My '57 Venom had exactly the same problem with a reluctance to start
hot. Try
a Champion N4C spark plug. Get the points in the magneto exactly right. I
replaced mine. Don't flood it, not much throttle either. If you think it is
flooded. Hold the valve de compressor in and swing the starting lever about
times. Try starting again without flooding.
#987 Just a few points which may help with poor hot starting - excuse any
that you
find pb obvious:
For a magneto to work decently it of course has to be in fair nick. The
gap is 12 thou. Plugs should have a gap of 18 thou (not 25 - thats for
electronic ignition) The usual plug cap is a resistor type and that is not
you want with a mag. Don't use a resistor type lead either - solid copper
the only one to use and forget resistor type plugs.
In case you are worried about interference, my Mk ! has no suppressors of
kind fitted and it causes no interference (as far as I know!) although I
it should.
In the past I have had trouble with Champion plugs playing up when hot,
always seem OK cold. I have used NGK for some years and they seem to cope
with hot or cold starting.
#988 Yes, the Venom, Viper and MSS shares the same valve angles ( and bare
casting) which I understand to be 35 degrees. The Thruxton valve angles are
33 degrees. You will of course require new valve seats.
#989 For interest how/why do non resistive plug caps and leads help with a
#990 does any body know the size of the front holding down bolt on the
dyamo strap
#992 This bolt at the bottom of the strap is part number SL8 15 which is
1/4inch BSF
x 7/16inch bolt. The bolt at the top of the strap is SL9 22 which is a
Whitworth x 13/16inch.
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#993 Resistor type plug caps, leads & plugs introduce a resistance into the
set up. Using any magneto it is a distinct advantage to reduce the
as far as possible hence leaving more power for a decent spark. This is the
reason for the smaller plug gap which encourages a fatter spark over the
smaller gap.
#994 If there is a good spark when hot, you are flooding the engine on hot
Just grab a fistfull of throttle (open it about 1/2 to 3/4 or so) and kick.
greater throttle opening will reduce venturi effect in the carb and pull
fuel and more air on the start, evaporating excess fuel accumulated in the
and getting the mixture correct. A hot motor will also cause a slight
of the fuel in the fuel bowl, possibly pooling fuel in the carb (this
varies by
carb type), causing flooding at hot start. Comments about the magneto are
applicable if the spark is weak when hot. Magnetos are velocity-challenged
kickstart speeds, generation of the correct primary current requiring
everything to be in good order for a hot spark. Resistance in the secondary
will limit their performance at start. Get rid of resistance plugs, caps
#995 I should add that certain resistance plug caps may increase resistance
time and with wear. A 30 year old resistance plug cap that started at 1000
could test at ten times that or more today.
#1035 when I purchased my MAC. it was
a poor hot starter until I found it had the wrong projection type
plug BP6ES instead of the standard B6ES .I know the MAC has a lower
compression ratio etc than the viper & venoms and that the magneto
resistance should be reduced to a minimum.But the reduction of the
gap to 18 thou instead of the velocettes recommended 23 thou,would
in the 50s & 60s be asking for wiskered up plugs. but that said we
did have Cleavland Driscole 101 octane petrol in the uk that any
old biker, will tell you made your bike go like a rocket. Are you
saying that the demise of lead in the petrol fouling, the plug is not
a problem now?
#1042 Was hoping someone could recommend Enging Balance percentages for an
Iron MSS (1946) and an Alloy MAC (1960). Both bikes are used as
regular rides, not racing if that makes any difference.
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#1044 The only information I can find for the MSS comes from P88 of
Burris's latest book.
"The balance factor was altered from 70% (iron MSS) to 55% (alloy MSS /
VM/VR heavy flywheel) influenced by changes in mounting methods. The bad
vibration in the long stroke engine was reduced. Later 65% was adopted as
the balance factor for the lighter flywheels"
Unfortunately I cannot discover the source of this information to validate
it. Based on my experience of the long stroke MSS, it doesn't vibrate
#1047 Stick to 70 percent. I once rode a friend's Clubmanized Venom, set
up to 55%, and it was the hardest shaking single I've ever ridden worse than a KTM Duke! My Venom was in bits at the time, and I
remember thinking, "If this is as good as it gets, my Venom is
staying in the boxes." But once he rebalanced it to 70, it was
fine. Don't know where Mr. Burris got his info, but it sounds like
bullpucky to me.
Another Veloist, one with more mechanical ability than most, told me
that he has measured several 86mm engines and has found that Veloce
used 70 percent on all. My experience with overweight pattern
pistons (which reduce the factor) indicates that you don't have to
stray very far from original to ruin high rpm smoothness.
Finally, I have a 1953 Cycle magazine with a 1000 mile test of the
swingarm MAC that quotes a 70 percent factor.
#1052 I have just
heard (second hand from Dad) that Phil Irving in 'Tuning for speed'
suggests 66%. It may be tin tacks in the end, but is it possible to
get a British single running smooth across most of the rev range with
only primary balance to play with?
#1054 regaurding engine balance there is a firm in holland
called dymo track. they are second to none as regaurds balancing.
they are the only firm i have ever met who can balance a triumph and
you end up with no vibration. they have very sopisticated machinery
to do the job, plus they understand motorcycles as martin the owner
has a norton comando which he balanced and he uses regularly. i dont
know if they have ever balanced a velo but i do know that they have
done goldstars. triumph cranks can be up to 100 grams out of balance
plus the wrong balance factor. he told me that sixtes triumps used
85% balance factor on the 650's and he told me that it is wrong and
the balance factor should be 74% add that to up to 100 grams out on
the crank and you get a vibro they do. there is also
the way in which the engine is installed into the frame....i.e. in a
different frame. twin downtube like featherbed or hung in the
frame...i.e. seely. the engine balance has to be altered to suit the
frame..i.e. the harmonics. check out dymo track, you might be glad
you did. plus they also heat treat conrods as they work harden and
become brittle. he told me that the celing for rods was 100,000kms
about 60,000 miles, after that you are in the red zone. after heat
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treatment you are back to as a new rod and you can start again.
#1056 I have good condition MOV flywheel ,big end ,etc. but the main shafts
I would like to change the shafts from MAC flywheel I have, witch main
is good condition but mess in the big end.
Question is how it could be done , and what I have to be careful to do
#1059 If you look at the inside of the flywheel you will see what looks
like a pin
between the main shaft and the flywheel. It is infact a threaded stud.
it and try to extract it with a broken stud extractor. If it's tight drill
it out.
Press the shaft out using a hydraulic press from the driveshaft side, take
care not to damage the thread on the end of the main shaft. Try to line up
the two halves of the stud holes and press the pin through from inside the
flywheel. Press the pin in until it is flush with the flywheel.Odds on you
will have to re drill and re tap the stud hole a larger size as the hole /
threads will not line up.
#1064 In 1969 I bought a Thruxton from Hall Green. It was
the smoothest solid mounted motorcycle I've ever
ridden. Yes, it's possible, but I haven't duplicated
it since.endeng
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Gearbox & clutch
#3 I have a 1969 Thruxton which is very difficult to change from 1st to
2nd gear.
#4 Having just stripped and reassembled my gearbox ten times to try to eliminate a non-returning
gear leaver I have become very familiar with the selector mechanism.
Firstly I would suggest you try to isolate where the problem lies i.e with the selector mechanism or
with the sliding gears and dogs. Firstly reassemble the gearbox with the selector mechanism only i.e.
camplate, forks, rods, etc leaving out the gears. Use a new gasket but no jointing compound and just
three bolts. Try the mechanism to see if the fault is with the selector mechanism. If all is OK, just add
the layshaft and associated gears and try this. Then try it with just the mainshaft and associated
gears. Hopefully by now you may have isolated the area in which the problem lies.
A few tips on the selector mechanism, I compared three different camplates and the notches were a
different form on each. On two of them they looked as if they had just been quickly ground out on a
hand grinder. With an oilstone make these notches a nice smooth transition, I found you could safely
“round” the edge of the notch to half depth. While the cam plate is out just polish the circumference
with the oilstone. Saying all that I don’t think the camplate is your problem, as you have tried two
different ones.
Next look at the striking pawl GC23/2. Two possible problems here. This may make contact with the
cam plate pivot on full travel, stopping the cam plate from fully engaging. The solution is to grind a
small amount from the hole, making it slightly larger at the contact point. Next culprit could be the
centralising lever BK99/2. The solution is to grind a little from either side of the crescent shaped cut
out i.e. having done that you may need to grind the back of the crescent to maintain clearance.
#9 Being new to my 1956 MAC, what are safe max upshift speeds on this machine? I have been
shifting at about 15, 30, and 40 miles per hour, taking into account the relative accuracy of the Smith's
Chronometric Speedo.
#10 Proper shift speeds for a MAC are 'before the valves bounce', preferably.
The mph would depend on your gearing. As Velo's are fairly unburstable, I
don't think it's much of an issue to worry about. I usually shift when the
model is no longer accelerating under full throttle.
just one man's opinion, Paul d'O.
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#12 Torque is fairly low down on the MAC, and on the wide-ratio gearbox, buzzing
it won't do a lot. 3rd. is at 75%, remember.
Always remember, don't slip the clutch
#14 The ratios are as follows with the standard 21 tooth final drive sprocket: 1st- 14 to 1, 2nd- 9.6 to
1, 3rd- 7.3 to 1, and 4th is 5.5 to 1. These don't seem to be particularly wide ratos. I do find, though,
that when I shift at an indicated 40 mph, speed drops enough so that I need to run a fairly wide
throttle to build up acceleration again to cruising speed.
#16 Over here, we work out gear ratios as percentages, so what you have is the
10- box, which has the wide-ratio gears the same as the MSS. I don't think
the actual pinions are the same, I think the box is a bit lighter being
drawn from the MOV rather than the "heavy" bikes. This on the MSS is called
the 14- box, and not all MSS had it, some had the Venom 12- box
A 5.5 ratio on a MAC is unbustable, that is, you can rev as far as you like,
you are not likely to get into the red zone. But on a 7.3 third, 70 mph is
already too much for sustained use, 50 in third the same, and 40 in 1st. is
about 7,400 rpm- we are talking racing speeds here. You tell us how many rpm
you consider reasonable.
To give you an idea of how wild a Thruxton is, the high 4th. gear (4.4 on a
20 tooth sprocket) is to try to limit revs in 4th. gear- usually we can get
to the maximum allowable, 6,200, in all four gears without trying too hard,
which is about 105mph in top.
On the Mac, you could go to 20mph in first, 30 in 2, 40 in 3 and you would
be revving to about 3,800 or so in each gear. I don't know peak power on a
MAC, but it is likely to be around the MSS figure of 5,000 rpm. You would
have nothing to gain revving beyond 5,000.
#151 I would be interested if anyone else sees this as a problem and also if anyone knows of a cheap
source of the large ballrace assembly. The last one I purchased was about £90 so I would not want to
replace it too often.
#154 I got mine from Grove Classic Motorcycles in Bedfordshire U.K. (+44 (0)1582 873066) as mine
was cracked and loose in the chainwheel.
I checked the price list and they are currently listed at £95
#157 Some new chain wheel bearings are a thou or so undersize (not necessarily those from Grove
Classics), and have a habit of dropping out of the chain wheel. Check the OD of the new bearing
against the old before you fit it.
#160 Sorry for the delay in getting back to you. Below you are the telephone numbers of UK suppliers
of reconditioned mags, I have not used them so I can make no recommendations. Some may only p
#160 my Venom has traveled just about as far in 13 years with the original
ballrace release bearing. It is adequate when properly lubricated. I was
slipping the clutch like a mad 125 GP rider on the way up Pikes Peak last
summer! Stinking SUVs...
Simple geometry says that the roller setup needs good lubrication too. If the
heavily loaded rollers on a crankshaft skidded like they do in the release
bearing they would not last a minute. I agree that someone with experience with
running a "dry" primary should give us some hard facts about bearing life. Race
bikes probably don't see the long-term clutch abuse that a street Velo does.
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Perhaps Mr. Zell could tell us a bit more about the Mondo Thruxton? Belt
primary? YZF-R1 clutch? How many miles?
#161 Reference the clutch release bearing saga, I modified the brass cage
on the bearing by filing it to take 3/16th" rollers after reading
about the mod in Fishtail in the 70's and never had to change any of
the parts despite using the bike as everyday transport for years
#162 When I had mt first Thruxton back in the late 60's ealry 70's it
seemed to "eat" thrust race bearings of the ball type. I now use the
roller type and find in the 10 years of ownership of my second
Thruxton I am still using the same bearing
#164 I have been using bonded clutches and better quality steel plates for
about 3 years now and find them a great improvement. I find that
neutral is easier to select, the gear change is smoother, also when
abused the clutch will go out of adjustment but return to its
original settings when "rested". I have found that the chainwheels
made in Germany do not last long and seem to wear very quickly. I
have just had them relined at Safetex in Yorkshire, but to date have
not had had the time or the weather to used them, has any one else
used Safetex relined chainwheels or plates?
#199 First comment is to correct the statement re non-listing of c.r.
gears for pre-war MAC/MOV. When iron MAC first came into the family
in 1978 I copied a parts book from old Joe at Allparts, Sydney,
(sadly no longer trading, although sister company, Modak, in
Melbourne is still going strong and does excellent mail order service
for things like 3/16"x3/16" rollers for clutch thrust race
conversions, .001" oversize rollers to revitalise tired drive side
mains on pre-war Velos etc etc). Anyway this book is marked "12/39
G.D." and lists B6/2AS sleeve gear (bushed) 16T (standard ratio) &
below that B6/3AS ditto 17T (close ratio). These pair with B86
layshaft driving gear 28T (standard ratio) and B86/2 ditto 27T (close
ratio). Now, Mick T's MAC definitely has the 17/27 combination (I
counted the teeth when he had the layshaft with the broken 2nd gear
on the table at the January Club Meeting here in Perth) and they are
as rare as... easiest way to go close ratio is to get a standard
ratio MSS sleeve gear and driving gear, grind down to suit MAC/MOV
width, then make suitable changes to the various spacers, sleeve gear
nut etc of the clutch so it will still operate correctly, as I think
the protruding threaded portion of the sleeve gear will be different
length to a MAC.
Oddly enough, the MSS parts book of that era lists 2 ratios, the
17/27 (BK8/2AS & BK86/2) being "standard ratio" and the 16/28 (BK8/3
& BK86) being listed as "wide ratio"!!! At least this explains why
there are a lot more 17/27's around for MSS gearboxes.
Only other source of new c.r gears for Velos I've found are the 18T
KTT sets available from Bob Jolly in Adelaide, but these would need
grinding to fit a MAC and I'm not sure we need 3rd and top to be THAT
close. If enough of us got together we could have sets made in Perth
from EN36 - enquiries have been made with the man who makes the gears
for most of the V8 Supercars (Ford and GM Holden tintops), but price
for only 2 sets is prohibitive. If I'm swamped with positive
reponses we'll include 2nd gear layshaft in the order as well, to
help get Mick back on the track and to fit to our racers to ensure
that bogey stays at bay.
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#207 I for one would be very interested in c.r. gear set for MAC.
To be viable I guess they need to cost less than the swing-arm
grind-down method. I havent been able to check how easy(how hard?)
this would be as I dont have a later g'box to look at...(I have
owned three different swing-arm 500s but now there's only the
Maybe someone happens to have both types in bits and could compare
Many years ago when I first had the Mac, someone told me that c.r.
gears were available in Sydney. I wonder where they ended up, or if
the info was even correct, seems it may have been if the parts were
once listed. I cant imagine many Macs would have been other than
'standard' ratio at the time when they were new, as for a generalpurpose machine and perhaps with a pillion as well they would be
struggling with anything else.
I'm not under any illusions about making the Mac into a 'racer',
but for the use I give it, the c.r. box would be a real improvement.
#208 CR 27T layshaft gears (B86/2) are available new old stock from the UK Velocette Owners Club
spares scheme, cost GBP 8.30 plus postage. I have just bought a new 17T B6/3AS sleeve gear for
GBP 36.00 plus postage. The Velo dealer that I bought it from probably has more; if any one is
interested please e-mail me direct (not via the group) and I will check this out and get back to you(Dai
Strangely enough I think you will find that B86/2 and B3/3AS was originally listed for the GTP as it
appears in the GTP spares book but not the MAC spare parts book.
#265 inFT319, the letter from Mr John Watson is very
interesting for me. Because the gear box shell I ever look at in
the autojumbles have problem there. Good one seems to be
In the letter, He made the oversize retaining ring with the left
hand thread.
I would be very interesting to hear that is such a conversion is
expensive business (I have to send out to the engineering farm
in UK)? Someone out there has ever done this? Where, how
much was it or do you know how to contact to Mr John Watson?
Yoshi 1598 (The year? Sorry,couldn’t resist,Les)
#266 Identification of gear cam plate
I supposed to have cam plate from prefix 4. But no parts number
on it. I do not know I can use it for the rigid MSS shell, etc.
My MOV racer is from totally bits of parts and still it is. And I am
no way to test it.
. ..
#267 Yoshi, John Watson is NOT part of this group, but is aware of it, He has
done this for himself and others, I will contact him for you and send you
his reply.
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#288 Judging from the way that ZUMAC ran
up the hills in top, I think that a 20 tooth gearbox sprocket would
improve things on both your S/A MAC and Zuma's iron head rigid. The
Book says yours came with a 21, ZUMAC with a 19.
BTW Dai, your spec page lists all 86mm 500 Velos as having 18T
gearbox sprockets as standard - the Red Book sez VMTs came with 20.
Of course, it also lists no standard sprocket at all for scramblers...
#423 I have a 1954 MAC and I want to rejuvenate the clutch. I have a few bags of
inserts from Martyn Bratby, enough to do all of the plates and the chain
wheel. Is it as easy as popping the old ones out and bunging the new ones
in? Or are there other things I should do as well?
#424 Plates must be reasonably flat.
Tabs to be deburred,
insert new inserts, put every 2nd one in then reverse plate,and finish off.
I have found that a dab of araldite holds the inserts in place , they tend to
become sloppy in use.
finally , a gentle sanding,( 250 grade wet and dry on a flat peace of glass).
The main thing is to use FLAT plain plates, most become dished with use.
A little extra throw at the lever ,till the clutch is bedded in will help
eliminate the drag.
#425 I agree with Chris replace them alternatively from opposite sides; you will
need to file the inserts with a taper to make them fit the holes. (Use
gloves and a mask). Inserting them will require some form of press, I used a
fly press but you may be able to do it in a vice. You will need to find a
spacer so that the insert can protrude through the plate –some people use
wire. To calculate the wire thickness, take the thickness of the plate away
from the insert thickness and halve it.
Remember there is two thickness of inserts 0.195 thick for the seven-plate
clutch and 0.155 thick for the nine-plate clutch..
#428 Why not send them to Sureflex at Clecheaton,
Yorkshire and have tehm bonded, saves a "pig of a
job"--- David Gibbison
wrote: > Tony
> I agree with Chris replace them alternatively from
> opposite sides; you will
> need to file the inserts with a taper to make them
> fit the holes. (Use
> gloves and a mask). Inserting them will require some
> form of press, I used a
> fly press but you may be able to do it in a vice.
> You will need to find a
> spacer so that the insert can protrude through the
> plate –some people use
> wire. To calculate the wire thickness, take the
> thickness of the plate away
> from the insert thickness and halve it.
> Remember there is two thickness of inserts 0.195
> thick for the seven-plate
> clutch and 0.155 thick for the nine-plate clutch.
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#430 Sightly wrong name its Saftek, 1 Rawfolds Ind
Estate,Bradford Rd,Cleckheaton, West Yorks. BD19
5LT.Tel 01274 862666 Web site
#451 I do have a running long term test question; I have had two of the new
'Canadian' clutches (with bonded linings from an automatic trans - I think
Goodman makes a version now) in my bikes. They have failed within 3000 miles
each, with proper adjustment even. Anyone else out there have the same
My Thruxton, a week before our annual ride, has terminal clutch slip.
Time to go back to standard
#480 I think you will be surprised to find that the 'demonish' clutch you took
apart is identical to the one in any Venom, MAC, KSS, etc! All Velo clutches
work beautifully if they are set up according to 'the book', and in this case
you could use the Red Book (factory service manual for Venom etc) to set up
the clutch, or ask any knowledgeable Velo enthusiast; they could help you set
it up in a trice, as undoubtedly they have done it themselves many times.
There are several sources these days for improved clutch parts, ie bonded
linings on the friction plates, slotted plain plates to obviate warping (not
so likely with such an, er, understressed engine as the model U), most of
which were developed to handle the power of a Thruxton engine on that same
little clutch.
As for you overhung crank, many prewar two strokes used them, including
Scotts, and while yours will likely do an 'end to end' run with no problem,
the advantage of this design is the ability to replace the rollers without
removing the engine! That's what that round door on your crankcase is for.
Not your grandson's Yamaha...
By the way, after surfacing my plain and friction plates on my Thruxton's
'Canadian' clutch, it has improved dramatically, and after some adjustment on
the first day of our annual Velo rally here in Washington stage, went
perfectly the rest of the week/1100 miles or so
#481 I agree with Paul, with the exception of the thrust and chain wheel bearing
you cannot use any of the modern parts as the clutch while operating on the
same principle needs components of different dimensions..
#521 I did the thrust race roller conversion many years
and many miles ago. At the time there was much
discussion about it's suitability, but time has shown
it to be the way to go.
Greatest advantage it zero wear and threfore zero
#529 I have a 1970 Venom Clubman, and could use some advice about the
clutch. I've done the clutch adjustment drill as carefully as I can,
and my clutch still slips under power. Should I dig in and take the
clutch apart to see what's going on, or should I try adjusting it
further to increase drag?
Since this is essentially a new bike, with just 12 miles on the
clock, and sat for 30 years, could it simply be that the clutch
springs are sacked?.
#531 Now I don't know if this will help but I had bad clutch slip on my MAC after
replacing the main bearings (I also took the clutch apart). Turned out that
I had replaced one of the plain plates the wrong way round. Thats all it
was. It was preventing the plates being sandwiched together.
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#556During a discussion with Don Chesson this morning the subject of a
weakness in the normally robust series 12 gearbox came up. Don is
Perth's elder statesman of Velo folk lore, having begun his racing
career on a Velo just as WW2 was ending.
If you refer to any list of bearing numbers for Velos you will see
that all the sleeve gear bearings B22 are the same from MOV to MSS to
VMT. Same for the layshaft bearing B22/3 or BK22 for cammies - one
bearing fits all. But when it comes to the mainshaft end cover
bearing the series 12 shares its bearing B23 with the MOV/MAC whilst
the iron MSS and cammies use BK23, a larger bearing.
Consequently it has been known for this bearing in the series 12
gearbox to fail or for the relatively thin bearing housing to crack,
with distastrous results. Don has recently obtained a butchered
series 12 end cover and is presently using it to make a pattern to
cast a few series 12 endcovers with enough meat around the main shaft
bearing to take the BK23 type bearing of the iron MSS and cammy style.
The strange thing is that I can't recall ever reading of this
weakness in the design and have personally never had a problem in
over 25 years of flogging VMT457 around the best biking roads in
Australia. But I've seen the results and know of a couple of people
who are currently looking for series 12 endcovers to replace broken
ones, so this isn't a figment of someone's imagination. The
recommendation is to replace that little RLS4 in the endcover of your
series 12 before it lets you down. They are cheap, readily available
at bearing shops and easy to get at for replacement.
And while you've got the endcover off, pull first gear off the
mainshaft, get your Maglite and take a real good look at the gears,
particularly the load bearing side of the teeth. At this age, there
must be many chatty gears still doing service inside the trusted
series 12 gearboxes of our Velos. I've had 3 apart in the last year
and I was hard pressed to make up one "good" set of gears out of the
three of them, such was the state of the hardening, particularly on
first second and 3rd gear layshaft and the double sliding gear. Not
surprisingle the gears with the most teeth seem to survive longest!
Has anyone else out there had a series 12 main shaft end cover
bearing collpase?
#558 I too have a stack of #12 gearbox end covers that are cracked around the
mainshaft bearing area. Two of them I know are the result of gearbox
blowups. And the good ones mostly have loose fits in the bearing bore. I'll
bet if you walk up to any Velo and yank in and out on the countershaft
sprocket you will find many with end float due to a loose mainshaft bearing
bore. On my VMT I have eliminated the circlip and use a sleeve that is held
in by the end cap to hold the bearing in tight. Haven't had a bearing itself
go bad.
All in all a good gearbox though and easily serviced. Count me in on one of
the new castings
#559 VMT 457 had a sleeve behind the inspection cover to locate the mainshaft
bearing (in lieu of the circlip) when we bought it in 1975. Rebuilt it with
new bearings in 1982, ignored the onset of tooth wear and got another 20 years
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out of it. Oil changes only and made sure water was kept out (using a
distributor cap rubber on the clutch cable entry - a must).
When rebuilding as a 5 speed this year, I noticed that the bore of the bearing
housing was threaded, same as iron engine gearbox endcovers. So I had a
threaded sleeve nut made up, like the pre-war gearboxes, and now have positive
control of end float. Sometimes, winding back the clock can be an improvement!
#562 During pull-down for rebuild of my 68 Venom Clubman I discovered that the
gearchange internal assembly of two yokes (GC56), connecting link (GC58) plus
clevises was missing in my gearbox, replaced by a short length of twisted strip
steel rivetted at each end. I assumed this was a temporary bodge fitted by some
previous owner, until I ordered all the bits and pieces from a supplier and
received - a short length of twisted steel with rivet holes at each end! Did
Velo decide, after years of the complex assembly, that a steel strip was just
as good? Should I chase the 'real thing' according to the parts book, or refit
its simpler alternative?
#563 The piece of twisted steel works fine and there is no real need to replace it
in normal use. If you want to reduce play in the linkage though I would suggest
that you obtain a pair of 1/4" "Rose" joints, one with a male thread and one
with a female thread, and an appropriate locknut. Screw these together and
adjust to the same length and orientation as the ends of the piece of twisted
steel. It may be necessary to shorten the threaded end on one or both parts in
order to get the required length. Lock the assembly together with the locknut
and a drop of loctite if you want to be doubly certain of things staying
together and use a couple of button head Allen screws and nylok nuts to replace
the original rivets and Bob's your uncle. If you're using a rearset linkage you
can replace the external clevis
#564 The length of twisted steel with pins inserted can easily be replaces by
'rose' joints (or Heim joints), as I've done on my VMT. The twisted steel is
fine for a while, but eventually the pins wear out their holes and sloppy
gearchanges result; a shame on such a nice gearbox. A retrograde step from
those early robust linkages, just as John Jennings found with the earlier end
Imagine finding a length of twisted steel in there, surely a bodge!
The length of twisted steel was discovered with much
shaking of heads and dealt with, along with all the
other linkages, in a manner still considered
appropriate. I toyed with the idea of bringing the
lever off the back of the box, but never got round to
it. The dreaded thrust race was fixed in a way that
caused much heated discussion at the time, but now
deemed the only practical alternative to constant
adjustment. The speedo cable was secured with a
mirror copy of the tacho cable holding clamp, after
watching a friend go down the road following a hasty
rear wheel change. I made a shouldered bolt in order
to insure the strap was firm and the clamp free to
twist in worst case scenario. The GP carb was
replaced with a MkII Concentric and air filter, being
far more suitable for the roads I was on at the time.
Never did get the jetting quite right and would be
pleased to hear from someone who did. The front
centre mudguard stay was made slightly wider to avoid
the repetitive breakages and the breather tube was
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relocated to act as a chain oiler. In hindsight, a
recovery bottle would have been more environmental
friendly, but at the time, staying clear of mother’s
oven with the Duckham’s tin made more sense.
Converted to coil springs which were all the rage
then, but not sure it was absolutely necessary. A
cover was made for the oil pump base plate when I
noticed leaks from the internal assembly screws. I
wanted to make a thicker base plate with blind
threaded holes to eliminate the problem altogether,
but lacked the expertise to get it right. Reluctant
also to remove the pump for what seemed a minor matter
at the time. Was not aware of the gearbox bearing
problem, but think failure is due to rust more than
its actual dimension, although why Veloce put a
smaller bearing in a more powerful machine defies
logic. Mine is secured with the circlip and still
quite firm, although I will give it a good looking at.
Hard to imagine rust causing problems on a Velocette
and what’s the bet most of that water was soapy? When
I installed the rubber boot on the clutch cable, an
enthusiast of the day commented about my machine “a
nice enough example, but a shame it’s not original”.
In all my tinkering, I like to think I have done
nothing that Veloce would not have got around to in
due course. In fairness, all the faults I ever found
were trivial and mostly due to the painful cash flow
sufferings of the company in those final years. They
could have saved a few bob with some subtle changes to
the SL list for example.
My bike (VMT 874) has weathered well and 32 years down
the track, I doubt there is a worldwide forum to wax
lyrical about the virtues of the DS-6.
Regards…..Tom Battisson Canberra.
#568 The length of twisted steel was discovered with much
shaking of heads and dealt with, along with all the
other linkages, in a manner still considered
appropriate. I toyed with the idea of bringing the
lever off the back of the box, but never got round to
it. The dreaded thrust race was fixed in a way that
caused much heated discussion at the time, but now
deemed the only practical alternative to constant
adjustment. The speedo cable was secured with a
mirror copy of the tacho cable holding clamp, after
watching a friend go down the road following a hasty
rear wheel change. I made a shouldered bolt in order
to insure the strap was firm and the clamp free to
twist in worst case scenario. The GP carb was
replaced with a MkII Concentric and air filter, being
far more suitable for the roads I was on at the time.
Never did get the jetting quite right and would be
pleased to hear from someone who did. The front
centre mudguard stay was made slightly wider to avoid
the repetitive breakages and the breather tube was
relocated to act as a chain oiler. In hindsight, a
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recovery bottle would have been more environmental
friendly, but at the time, staying clear of mother’s
oven with the Duckham’s tin made more sense.
Converted to coil springs which were all the rage
then, but not sure it was absolutely necessary. A
cover was made for the oil pump base plate when I
noticed leaks from the internal assembly screws. I
wanted to make a thicker base plate with blind
threaded holes to eliminate the problem altogether,
but lacked the expertise to get it right. Reluctant
also to remove the pump for what seemed a minor matter
at the time. Was not aware of the gearbox bearing
problem, but think failure is due to rust more than
its actual dimension, although why Veloce put a
smaller bearing in a more powerful machine defies
logic. Mine is secured with the circlip and still
quite firm, although I will give it a good looking at.
Hard to imagine rust causing problems on a Velocette
and what’s the bet most of that water was soapy? When
I installed the rubber boot on the clutch cable, an
enthusiast of the day commented about my machine “a
nice enough example, but a shame it’s not original”.
In all my tinkering, I like to think I have done
nothing that Veloce would not have got around to in
due course. In fairness, all the faults I ever found
were trivial and mostly due to the painful cash flow
sufferings of the company in those final years. They
could have saved a few bob with some subtle changes to
the SL list for example.
My bike (VMT 874) has weathered well and 32 years down
the track, I doubt there is a worldwide forum to wax
lyrical about the virtues of the DS-6.
Regards…..Tom Battisson Canberra.
#574In the following for gear shaft nut please read sleeve
gear nut. I've two clutch spring holding assemblies
#1 is a one piece unit,max depth 5/8", with four sets
of four spring holding holes,with springs presumably
3/4" long when new.
#2 is a two piece unit max depth 7/8" with a separate
spring holder containg 16 equidistant holes.No
When I ordered a set of clutch springs for a 7-plate
clutch from VSL they turned up at 1 1/8" long.
I've only one gear shaft nut which is 7/16" long.
I can get the nut on to set #1 and the clutch works in
this mode;but to try to get it on to set #2 I'd need
to be Britain's Strongest Man.
Is there a gear shaft nut with a longer thread,or have
I been sent the wrong length of new springs,or what?
Both sets would seen to fit behind the gearbox
sprocket with sufficient clearance.
Why is a 21t gearbox sprocket as indicated in the
Spare Parts Catalogue (SL 94/1) not listed in any of
the current main suppliers catalogues(it is listed
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under Viper bits);has it been found to be unsuitable?
Finally,the gearbox nut locking piece.When countersunk
mine has the thickness of a fag paper,so what does the
little 1/8whit csk screw into?
#576 hello, a 21 tooth sprocket is very very tall, and a bike would
struggle to pull it. my venom has a 19 tooth fitted and it works spot
on. i fitted a 20 tooth and it was too tall. fitting a 21 tooth would
be way too tall for a 500 and a 350 would never pull it. i guess the
demand for a 21 tooth is next to zero, thats why they are probably
not listed.
#650 Please someone tell me the parts number of the gear box end
cover ball bearing for prefix 5.
#651 I am not familiar with all of the various gearbox serial numbers and their
potential similarities/differences. I can tell you that this bearing in my '50
MAC is a FAG LS5. Readily available, at least here in the States.
#681 Could you please suggest any remedies for an oil leak from the kickstart
ratchet box, it appears to be coming from the shaft. Is there any way of
fixing it apart from buying a new box?
#682 Try here
#683 I used a 19-27-4 single lip seal obtained from Bearing Services Ltd.,
into a 4 mm deep recess carefully bored in the outer face of the kickstart
housing. The shaft was carefully deburred and its diameter cleaned (if it's
pitted or damaged the seal will not last long) and eased through the seal
so as not to damage it with the flat for the cotter pin. The lever was
as normal, being careful that it didn't slide back through the seal during
assembly, and the whole assembly then fitted back into the end cover as per
manual, but with a thin smear of Three-Bond silicon sealant on the mating
to seal it. This part of my machine has been totally oil tight ever since.
#685 There are people who will do an exchange or conversion with an O ring
fitted to stop the oil loss. Colin East on 01522-810029 does, I'm sure
there are others too
#686 Some years ago, I tried to cure such oil leaks and followed the advise
found in
FT Hints and Tips. So I get the housing machined to fit an O-ring. This
to be an improvement for a while, but seepage came back, although less than
before, as 0-rings are not designed to cope with repeated rotations, and
wear. Especially if there is some wear in the assembly.
I'm now considering to fit an oil seal instead.
#694 A quick remedy to ameliorate the oil weep from the kickstart housing
without recourse to machining it,is to epoxy-resin a thin oil seal
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1x3/4x1/8 imperial obtainable from a good bearing stockist for maybe
£2.00,to the outside of the housing cover over the kickstart shaft.
This may sound a bit of a bodge but it does work without interfereing
with the kickstater engagement.
#786 Rebuilding a '69 Velo Clubman I've had an early introduction to the
clutch. Took it apart, fitted new inserts, and put it back together again.
Great, except that tightening everything up now leaves the clutch springs
almost fully compressed with no movement to allow the clutch to disengage.
I've read all the technical notes on the web, pulled it apart ten times,
still no joy.
As best I can see, relining the plates should make no difference. The
sandwich of plates is no doubt thicker, but the spring holder is
independently adjustable to accommodate this. What happens when I try to
screw the sleeve nut on is that the springs compress until they are
virtually bound (i.e. about 20 mm) before the sleeve nut can tighten
the boss in the back plate to secure the clutch assembly. Winding the
holder further in simple presses it against the thrust pins and starts to
disengage the clutch.
Incidentally, in case it might be relevant, the chain wheel is well out of
alignment with the engine sprocket. The wheel would need to be 4-5 mm
to the gearbox for alignment, although the tooth wear suggests it's been
running out of plumb for a good while. All very odd. The clutch was
and operating properly before disassembly and only the spherical thrust
washed has been renewed, because of pitting.
#787 Sounds like you have fitted the chainwheel, back to front?
#800 Many thanks for your reply. It would certainly put the chainwheel in
alignment, but unless I've misread every reference I can find, there are
four plates between the back plate and chainwheel, and only two plates
between chainwheel and front plate (which is why the chainwheel has a
shallower rim on this side). In other words it's not possible to fit the
chainwheel back to front.
#803 I think you've misread the references. There should be two plates
between the
backplate and chainwheel, and four between the chainwheel and front plate.
later clutch was (as is normal with Velos) a development of the earlier
whose basic design was the same, but which had two fewer plates. These were
added on the outer side of the assembly to cope with the extra output of
later engines, but without having to change any more components than
so the inner side of the clutch remained the same with only two plates and
original chain line was kept. The shallower rim therefore fits to the
(towards the backplate). Contrary to what you say, it IS possible to fit it
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wrong way round, but you would also have to stack the plates wrongly too.
other thing to watch for is that the bend on the tabs of the plates is in
right direction. From the top of my head and without reference to the
the bend is away from the chainwheel on either side. Should be obvious with
bits in your hands - things will touch if you get it wrong!
#805 Who has misread the references? With backplate fitted to a disused
sleeve gear held in the vice.
And quoting directly from the red book: "Fit the first clutch plate
in position followed by a spacing plate, second clutch plate and second
spacing plate. Note that the external tongues on the clutch plates and
internal tongues on the spacing plates
must all point away from the chainwheel, i.e. downwards."
It goes on to say centralise all the plates then fit the chainwheel
with the deeper slotted rim underneath.
It continues "With the chainwheel fitted put on the third spacing
plate and clutch plate in that order and with their tongues pointing
upwards." It says centralise the plates and fit the front plate.
Personally I agree with Chris Wood and message 787.
#816 Sorry everyone, I stand corrected. Just checked the books and Tony is
of course
correct. That'll teach me to jump in feet first without checking my facts!
Can't see how the chainwheel can be fitted back to front with all the
plates in
the correct order though. The only other thing I can think of is that the
plates have become displaced during fitting to the sleeve gear splines.
#827 Are you sure you haven't fiited the thicker 7 plate inserts in error?
#829 Many thanks for your suggestion. The inserts I've used came with the
amongst a batch of 25 year-old spares. I soaked them in oil to soften them
and fit them more easily. Maybe they've swollen? They are about 9/64ths
thick, say 3.5 m.m. Forgive my ignorance of the 7 plate clutch. Do my
inserts sound like the wrong ones?
#833 New VM style inserts are 1/8" thick. The earlier type are close to
Is it possible that when you put the clutch back onto the sleeve gear you
forgot to fit the loose sleeve on the sleeve gear first? Maybe also, even
though you used the old one, is it the correct nut? They came in two
the longer one being used for the 9-plate clutch.
Are you using the correct length pins for the release mechanism? Or did you
'new' big-end roller without shortening them?endclu
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Fuel, Oil & Oiling System (for oil pump see Engine)
#143 I had a Venom Club, and from time to time, possibly connected with
bore wear and engine speed, it spat out considerable quantities of oil via
the engine/oil tank breather. A friend, more thorough than I, believed on
his similar Club it was the oil frothing too much and thought he'd pinned it
down to a certain make of oil- we're talking of 25 years ago. The only
result was I checked engine oil, as a reflex, every time I stopped.
#145 I'm wondering if the MAC puts out less oil mist then the higher powered units, if the pump is a
lower volume pump then the venoms. If not it means I have plenty enough oil flow. Interesting thing;
when I run up the rpms, on the center stand with the oil tank cap off, the oil is seen to be flowing back
into the tank but not under much pressure, and in sort of a pulsing flow. Is this normal for the
Velo? So many details, so little
#146 This pulsing flow is very normal on Velo
returns. According to the manuals it's due to the fact
that the return side of the oil pump has a greater
capacity than the supply side-this is designed to
avoid the possibility of crankcase flooding.
On matters like this I'm in agreement with
Bruce's recent comments- Velocette were not theorising
when they built their bikes ! How many TTs did they
win ?
Just to add to your comments, and I agree with your observation that
Hall Green had a pretty good idea what they were doing!
Regarding engine breathing: updating the engine to the latest Velo
spec is about as good as you will get. This involves drilling through
the back of the timing chest into the main crankcase and fitting a
breather outlet adapter in the back of the timing case underneath the
magneto. A pipe should lead from here to the oil tank which doubles
as a separator, the oily stuff stays in the system and the acidic
gases then escape to atmosphere via the tank breather pipe which
should lead out to the back of the bike. This should NOT be returned
to the chaincase or led in a misguided attempt to lubricate the drive
chain. Either of these options will result in premature failure of
either chain due to the corrosive effects of the breathed gas.
This system is very similar to those used on many modern machines and
in racing, the only real difference that nowadays the gasses are led
back into the air box to be taken through the induction system and
burnt as part of the emission control system. If everything in the
engine department is in good condition you should find that the
machine remains pretty well clean and dry, and there should be little
or no fluid around the end of the tank breather pipe. If the breather
under the mag is led simply out to the rear of the machine you will
find it very quickly covered in oil!
Pete C.
--- In [email protected], "Bruce McNair" <[email protected]> wrote:
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> Warren,
> I've seen some weird systems with standard chaincases. One, probably
> practical but not too pretty, was to weld a "blister" down the
bottom of the
> chaincase, to increase the capacity. Another guy put his engine
> into the chaincase, not the oil tank.
> Some schools of thought say to take the engine breather, the one
under the
> mag, straight out the back of the bike. This, they claim, avoids recycling
> sulphur-laden oil back to the engine. This breather can be retro
> Stay around long enough, you'll hear everything from the brilliant
to the
> dangerous in mods. As you say, if there is a real need, probably
> can be done nowadays. Somebody over here says to take the alloy
tube out the
> centre of the filter. The purpose of this tube, as fitted by
Velocette, is
> to stop the oil in the filter going into the crankcase when the
motor is
> stopped, and the Velo attitude seems to me correct. Never assume
you know
> better than Hall Green: they were pretty practical fellows.
> Bruce.
#179 The modification to the 1960 V models uses two pipes and the length of both
is important, but probably not critical. The lengths prevent the
Pressure/Vacuum from syphoning the oil.
Steve of R F Seymour, The Velocette specialist, will inform as my information
has gone "walkabout".
Tel +44 (0)1 844 212 277
#180 I have not used my 1947 iron MSS (called
"Eugene", after its designer) much in the last three years or so
since leaded fuel pretty much vanished. On pump unleaded (95) it
seems to run ragged at revs and much hotter (straw exhaust pipe for
the first time ever - I do not thrash it as a rule). Does any one
out there have any experience of carburation with UL fuel? Do I need
to re-jet? The valve seat recession thing can be dealt with by
addatives and I cannot believe that I need an octane booster with the
MSS at around 6 to 1 CR! All ideas gratefully received.
#181 I used with great sucess on my Thruxton a Moto Guzzi
Le Mans Mk1 breather collector box fitted under the
seat at a greater hight than the oil tank. The
crankcase breather pipe ran into the tank via a one
way valve in the box, another pipe ran into the oil
tank and a third pipe breathed to atmosphere. The box
needs a bit of modifying, but is well worth the
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efforet. Royce Creasey described the box in an
article on engine breathingseveral years ago in
Motorcycle Mechanics
#183 We Veloist here in West OZ have had all sorts of problems with the lead
replacement fuel which replaced the old "Standard"
fuel. Plugs foul after only a couple of miles, engines run roughly,
impossible to time the engine - Yech!
The only solutions we have found to work are either using the combined
octane booster/upper cylinder additives in conjuction with the highest
octane rated Unleaded fuel we can get, called Premium Unleaded down here,
which works well.
It certainly does not work using the additives with "ordinary" unleaded
The best solution and one that makes the old girls run as sweet as can be is
to use Avgas (100 Octane avaition/racing fuel)
at a ratio of about 25% Avgas to every tank of unleaded fuel.
This has worked for all our machines from pre-war to Thruxton
RE; the unleaded fuel debate. We in the USA have had unleaded fuel for about
12 years, and I am happy to report that it required very, very few changes to
jetting or valve seats. There was as much fuss here at the time of the
switch as you are experiencing, which all pretty much went away with time.
Yes, the octane is lower, so no more 10:1 pistons, we find 9:1 the limit
on a Velo. Some (VERY FEW) bikes have had problems with valve seat
recession, in fact the only bike I ever consistently heard with this problem
are BMW R 100's of a certain year. I don't see why a bike with an iron head
and 7:1 piston would need Avgas, it will run hot certainly. Some unleaded
fuel has extra alcohol here, which can make some bikes run lean, a simple
adjustment is all that's needed.
Don't panic, everything will be just fine.
yours in anecdotal evidence, Paul d'Orleans.
#190 Listed in the parts book the respective lengths are FA138 Engine to oil tank 21.375 inches,
FA141 oil tank to wheel(!) 27.5 inches
#195 You are spot on, but I have never found whether this includes the coupling at
the engine end.
The inlet to the tank is at the back and I will find the dimensions and
The vent from the tank to atmosphere is from the rear and at the top of the
froth chamber.
#197 Just a quick comment on the use of 80/90 gear oils in Velo gearboxes DON'T!!!! Especially if they are Hypiod type oils - REALLY DON'T!!!!
The recommended oil for a late Velo gearbox is a 20W50 multigrade
engine oil - Hypiod oils will attack the bronze bushes in the box and
cause eventual seizure - the sort of increased friction you can do
#350 History- Top end rebuild about 6 years ago but to my knowledge the
bottom has never been touched.
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SymptomThe bike has been unused for about 2 years, so the sump had filled
with about 1 cup of oil in that time.
After draining this and starting the bike the engine smokes for about
2 minutes then stops smoking and runs cleanly for appro another 15
minutes then resumes smoking quite heavily.
After re inspecting the sump I find about 2 cups of oil unscavenged
back to the oil tank.
I have been told the Velo pump is fairly reliable a gives little
trouble, I have investigated all the simpler possibilities but to no
Checked and washed filters in the circulating system.
Plenty of oil is getting to the top of the motor etc
Checked and cleaned return lines to tank,no blockage found.
Checked that the oil tank is not pressurising (and ran it with the
cap off there is a constant flow)
Checked if overflow was blocked or kinked. OK
Has the pump had it ?,and were do I find a replacement in Australia.
or and I hope,could it be
that the gear/shaft of the pump has warn a groove into case endplate
and on heating up the gap increases far beyond spec (which I don't
know) an the pump fails on the return.
If this last point is a common problem could somebody let me know,and
would refacing the casing on glass with lapping paste solve my
#351 I also have a smoking MAC, a 1952 Alloy engine.
My Mac started smoking after winter storage several years ago. It
also accumulates oil in the sump, but after draining that oil it will
continue to smoke and oil will ooze from the exhaust port. It has
been sitting in storage in my shop office trailer ever since.
Several people have told me, that my engine probably has a broken oil
scraper ring. That it probably rusted to the cylinder during the
winter. I did neglect to pour a small amount of oil into the
sparkplug hole before storage.
I just bought a blue shop manual reproduction on eBay, that covers a
lot of motorcycles other than the MAC. Better than trying to go in
blind I would think.
#352 Have you cleaned the filter PLUG at the bottom of the crankcase
7/16" BSW Spanner
#353 Don't know your full case but I would strongly recommend that you investigate the oil return,,,, it
sounds like the oil accumulating in the crankcases cannot be transferred back to the oil tank quick
enough !!!.
#410 I'm having problems locating 40 grade oil for my Venom in Ireland.
Does anybody know the location of a supplier? I am relucant just to
top up with Multigrade as I don't know the history of the engine vis
a vis rebuilds etc.
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#412 I wouldn't use a multigrade after a straight 40.
They deliver free for orders over £30 in UK mainland.
or you could try Silkolene who also do a straight 40
There may be other suppliers of Silkolene oils..
#421 fill up with Shell Optimax, they make some rediculous claims
- however it has transformed my Venom, no more pinking the
acceleration and performance is back to what it was on 5*.
#438 It’s a well known fact that petrol does go off rapidly, I find even two
month old petrol will hamper starting. There is even an additive to add to
lawnmower petrol to stop it going off.
#439 Thanks for the note. I've often heard people say that petrol `goes off' but
have never experienced this. Even when the bikes have been sat in the garage
over the winter they don't seem to have any fuel problems. Maybe in the
colder weather the volatiles don't evaporate so quickly. Anyway, I'll get a
fresh gallon tonight and see what happens.
By the way, I've been using your Velo Technical website a lot during the
rebuild. Very useful site..
#440 Don't know if it is available in the U.K., or if you have your own
version there, but there is a fuel stabilizer here in the States called Stabil,
which works well in diesel and pump gasoline. I have literally used 6 month old
gas that has been treated with it, and the vehicles ran fine. Might be worth
looking into. I have the feeling the quality of pump petrol in your
geographical location is poorer in quality then what we have here. My
impression, at least..
#443 Here in the USA, if fuel is in a vented tank, such as a motorcycle
tank, and sits a year of so, you can't light it with a match!
Fresh fuel and a new plug should do it..
#482 We cured most of our oil leaks by changing from a modern multi-grade to
Castrol GP50.
Last Sunday at the Tyne Valley Classic Motorcycle Club show we were informed
by an IQ0 that Velocettes were never designed to run on straight oils.
He had so many modern reworked parts on his bike the only thing missing were
the Honda badges..
#544 I have recently built a Venom engine out of parts obtained from
various jumbles and other sources. the oil pump has been checked and
is in excellent condition and there are no obvious air leaks. The
problem is when I fit the ball valve no oil will feed to the
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rockers. Remove the ball valve and instant feed is there. Anyone
had this problem before??
#545 Probably too obvious, but have you put the ball and spring in the right
way - ball on top of spring. Also the seat for the ball needs to be almost a
knife-edge for it to work efficiently. If you can see a clear chamfer where
the ball sits on the seat it is probably too worn. Also obvious check again
for air leaks, even a pin hole will upset it.
#546 Make sure you prime all the air out of the delivery oil pipe so that the
negative pressure exerted by the oil pump will suck oil past the feed valve.
You can, initially, pressurise the oil tank to do the same job.
The elasticity of any column of air in the pipe will forestall this.
We note the comments about ensuring the ball is the correct way round in the
valve assembly.
We have never had any "sumping" problems with any of our Velo's.
#584 As told previously, I got some noticeable quantity of oil coming off the
crankcase breather line.
As seen in Parts List, would that help to drill a vent hole in the oil tank
filler cap eventhough there is already a breather line fitted to the oil tank ?
#596 The hole in the filler cap is about 1mm in diameter so it has a marginal
effect on breathing, however if it's like my Venom the hole will ensure that
your leather trousers will require little in the way of preservative. A
fellow VOC member who has researched the topic of oil levels has recommended
the level to be 55mm below the top of a short necked filler cap.
#597Having previously posted a question relating to occasional crankcase oil
flooding in my '50 MAC (only occurs at sustained high RPMs), I now suspect that
it is attributable to pressurization of the oil tank. When I obtained this
bike, it had no vent lines of any sort, and an unvented cap. Unfortunately, I
am currently prevented from verifying this theory, since having lost top gear
two weekends ago, the internals of the transmission are adorning my workbench.
Hopefully, I will fix the latter problem, and have a more definitive answer
Ironically, while looking at a '47 KSS that a friend recently obtained, I noted
a tube that emerged in the vicinity of the rear mudguard and remarked, "What's
that. I don't have one of those."
So it does appear that properly venting the tank/return leg of the oil system
is critical. My question relates to how much venting is required. Apparently,
most [all?] bikes equipped with a vented cap had a vent line as well. Is a one
millimeter hole in the cap really adequate, or should I add a vent line to the
oil tank? I believe the originals were on the order of 1/4" I.D.
#598 Having similar problems with a 54 MAC- flooding the crankcase after a
reasonably hard run, I have no additional breather other than the 1mm hole
in the oil tank cap either.
However my main intermittent problem which may be related has been -getting
far to much oil into the combustion camber at start-up. Obviously splashing
up from the crankcase literally heaps of white smoke for about-10-15 minutes
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far to much and long for just a guide wear draining back issue and yes my
valve guides and rings are tired). I have fitted a new ball/spring/seat in
the one-way valve to no avail and have checked for air leaks the pump is
also returning a good flow, which is basically constant.
Being a novice looking for advice, and not knowing the correct oil level for
the tank-I have been experimenting and found that lowering the oil level in
the tank to just below half and changing to a straight 30 grade oil seems to
reduced the problem considerably.
Is there a correct ration re oil- tank volume and engine/oil line capacity
that determines the correct oil tank level or have I been basically
overfilling the tank ?
What is the approximate volume of oil that should be left in the crankcase
after standing overnight?
Like to know more about additional breather set-ups.e
#599 The breathing system on older Velos is a bit marginal to say the least, and if
no other breather is fitted to the oil tank other than the 1mm hole in the cap
it's no wonder that at times the cases will flood. My Venom always had a
breather on the back of the oil tank which internally went up to the top of the
froth tower and externally was led via a 3/8" bore pipe out to the back of the
machine to atmosphere. This always provided adequate breathing even when the
machine was modified to the later engine breathing system where an adapter is
fitted to the back of the timing case below the magneto and the 1/2" bore pipe
leading from this breathes into the oil tank. I don't have a vented cap and
have no problems with excessive amounts of oil smothering the machine or my
leathers either! The engine does still breathe into the chaincase through the
hole in the drive side mainshaft as well and although this has recently been a
bit excessive and necessitated regular draining of the case, I've recently had
the oil pump overhauled properly for the first time in its life and hope that
this will cure that particular problem. I think that a 1/4" bore pipe would be
a bit too small to do the job right, and you should remember that if no froth
tower is fitted to your tank you are very likely to have a big problem with
excessive external lubrication, since the function of the tower is to separate
oil from breathed vapour.
#601 All this talk of oil levels / oil breathers reminds me of a story the late,
great Phil Irving used to tell. During his first stint at Veloce, he took it
upon himself to point out to Mr Percy that the oil tank transfers were
misleading and impossible to abide by. When queried he explained that the
wording "Keep Oil Above this Level" literally meant that the oil tank had to
have oil in the top and only air below the line on the transfer. He was told
to mind his own business.
Later models had a subtle change to the wording - something simple like
"Minimum Oil Level". So one can presume that Mr Percy took note of this
comment, having slept on it.
On the subject of oil level and its effect on engine breathing, early
experience with VMT 457 and many other late model Velos shows that if you
overfill the tank it will pump oil out the breather system until the level
stabilises at about 50 to 60 mm below the top of the filler. So one soon gets
an eye for the level which avoids excessive waste, with the extra oil simply
blown all over the machine, whilst keeping enough in circulation to cool and
lubricate. By the way, I've never been one to be too concerned about what oil
goes in - sometimes special (expensive) 4 stroke oils, and sometimes cheap
generic brand mulitgrade (as long as its API spec was SE or higher) and they
all seem to work - never a seizure and now completing the first major overhaul
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in 20 years with nothing more than a hone, new rings and fitting a better
second hand Nimonic exhaust valve (the original was pitted because it was only
a KE965 to start with and obviously didn't survive the degradation of fuel
quality these past 4 years or so). Oh and I did do a bottom end overhaul as
well, not because it needed it, but because I didn't want to be having to pull
the engine out again within the next 10 years. And the engine was only sitting
on the bench in the first place because I needed to remove the gearbox - give
me an iron MOV or MAC any day!
And those who have toured with VMT457 will vouch that its longevity has little
to do with a gentle hand on the throttle.
#604 My good, and lamentably late friend John Anderson used
to reckon you should just be able to touch the oil
with the tip of your finger. Saves looking for a
depth gauge every time.
#605 I also had a '47 KSS ( why did I ever sell it??) that had a breather pipe
extending to the rear mudguard and never had the slightest problem with oil
levels or useage - in fact I never had any problems of any kind over the 8
years of using the KSS. My "new" '61 Venom has an unvented oil tank cap but has
the half inch breather pipe referred to by Pete C. In this case it is directed
to the chain just by the footrest/brake pedal ( Clubman rearset). I have tried
overfilling the oil tank - to see what happens! - and it simply blows oil out
onto the chain , which ends up on the tyre, rim etc, until the level in the
tank is back to more or less half way between the max and min level, the level
seems to stay there then irrespective of whether I'm in ride to work mode or
having a long thresh down the M4.
#606 One point I perhaps ought to point out re breather vent pipes is that they
should NEVER be routed to discharge on to the chain. Whilst it may seem to be a
good idea to lubricate the chain with any vented oil, the breathed vapour is in
fact acidic and will shorten the life of the chain and sprockets if allowed to
exit in this way. The best place I have found is to lead the pipe (whose length
is specified in the parts book and is important for correct operation) out of
the rear of the machine by ty-rapping it along the underside of the nearside
rear mudguard stay
#607 Interested in the comment, "if no froth tower is fitted to your tank you are
very likely to have a big problem with excessive external lubrication, since
the function of the tower is to separate oil from breathed vapour."
Specifically, what is a frothing tower? Perhaps a failure in my British to
English translations skills is at play here? The return pipe in my oil tank
does stick up about an inch above the oil itself (setting aside the rather
active dialog about where to properly set the oil level). Is this the
tube/tower that is being referred to?
I was also fascinated by Pete's remark about the, "lead the pipe (whose length
is specified in the parts book and is important for correct operation)." With
due respect, the pressure drop in a 1/4" line at the flow rates in question is
relatively minimal, and I fail to see how the exact length would matter
whatsoever. We're not exactly talking about the reflected back pressure wave
in a tuned exhaust system here.
#608 Do you mean that a pipe shall be routed from the crankcase oil breather the the
small tube at the battom inboard side of the oil tank ?
I expected this small pipe being a breather outlet ?
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#609 The small tube at the bottom of the oil tank must be blocked and takes no
part in the breather system.
A hole is drilled and tapped into the crankcase just under the magneto. A
screwed hose adaptor is positioned and a 12mm plastic pipe attached.
A hole is drilled into the back of the oil tank and a 12mm tube brazed or
silver soldered to place. The dimensions and angles are fairly critical. (I
have them somewhere)
A second hole and tube at attached to the top, rear, of the froth/foam tower.
The tube from this is lead to atmosphere.
The dimension of the lengths of the two tubes are critical if the pulsations
created by the positive and negative pressured in the crankcase or not to
cause a pumping effect and evacuate the oil.
Also the vent hole in the oil tank cap should be blocked.
#612 Could you provide me with the dimensions so I could modify the breather system
on my Venom ?
#614 Oil filter tube , If the fibre gear stips it will certainly
block up the oil return , I've had it happen in the past and a friend
had it happen only a few weeks ago on a club outing , the pump
pressire split the return line . I do NOT recommend removing the tube
from the Filter , When the engine stops all the muck in the filter
will drain down with about a half pint of oil back into your crank
cases , a) it makes it difficult to start with all the oil drag (
espcially cold), oover oils the engine till it all clears , c ) think
of all the grit ,swarf and silicine that is in there !
Nots /bolts for the MOV . I don't know of anyone who does
Kits , but the VOC have many bolts sized according to listed part
number/length /thread .
#619 No, most definitely not. You are right to say that this is the breather outlet.
For the original Venom/Viper/Endurance/Scrambler/MSS/Clubman tank this is, if I
remember correctly, a spigot for a 5/16" bore pipe, 11" long which is clipped
to the rear mudguard in front of the rear wheel - a positively diabolical place
to locate it if you are prone to overfilling the tank! I do know that you have
had some details from Keith about the later crankcase breather mods so I won't
elaborate on these other than to say that the position of the outlet on the
back of the timing chest is quite critical and there is only a very small space
to fit it! There is a cast wall which surrounds the bottom circumference of the
magneto pinion inside the timing chest, below which is a small almost
triangular area which is the target to aim for when you drill through from the
back of the case. If you drill above this the hole will be shielded by the
pinion which will then proceed to pump oil out at an alarming rate. In addition
a 1/2" hole should be drilled through the back of the timing chest into the
crankcase. I'm not sure of the exact location for this and since my engine is
currently in one piece I do not intend to take it apart to find out! I do
believe however that it is documented in back issues of Fishtail.
#620 the froth tower is the name given by
someone in Velocette history to the inch and a half diameter tube that rises
from the top of the oil tank by about two inches inboard of the right hand
frame tube. Inside the tank there is a tube running from the top of this tower
down to the back side of the tank with about an inch sticking out, to which a
flexible pipe should be attached and led to the rear of the machine. This is
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the tank breather outlet. I believe that the purpose of the froth tower is to
keep the end of the tube inside the tank well above the level of the oil or any
froth (air/oil mixture) and to prevent oil from being discharged via the
breather. I cannot tell you whether there is any additional baffle incorporated
in the tower, perhaps someone else might be able to enlighten us? When the
later type engine breather system is fitted, the pulsations in the crankcase
are transmitted into the oil tank via the 1/2" bore pipe, and yes, there is a
tuned length to the system. The factory worked out the lengths of the pipes and
if correct, the system is quite effective. If not, the system has been known to
pump oil out and lubricate the rear tyre. The return feed to the oil tank from
the engine enters the bottom of the filter chamber which is about 2 inches
diameter, and runs up the inside of the aluminium tube that surrounds the
through stud retaining the top and bottom caps on the chamber and prevents
unfiltered oil from returning to the crankcase through the scavenge side of the
pump. Oil flows then through the filter and returns to the main body of the
tank through the short tube to which you refer, just below the filler cap.
#623 having read your detailed description of the frothing tower,
crankcase breather, vent lines, etc., I can only observe that my '50 MAC as I
received it does not have any of these features. It has a sealed oil tank with
two tubes entering at the bottom. One is the feed union, the other the return
pipe which is an integral part of the tank itself. That's it. I spoke with
fellow who restored this machine, and he says the tank, crankcase, etc. are as
he received them (i.e. no vents anywhere). I did not think to ask him if the
unvented cap is a replacement. It's essentially perfect appearance indicates
that it is most likely not original, and may be incorrect in that it is
I only began thinking about any of this when I encountered a scenario wherein
the crankcase floods with oil, but only after several minutes of sustained,
high RPM operation. Otherwise, everything appears to function properly. I
noticed that there are no vent lines whatsoever on the oil tank itself (or
anywhere else for that matter), and that the oil tank cap is unvented as well.
In looking further, I noticed that a vented cap is available, which reinforced
my notion of the possibility that the tank is probably pressurizing.
Unfortunately, my scheme [notice the overt use of English phraseology] to
explore this theory by temporarily replacing the cap by a stopper with a
reasonably large (1/4" or so) hole in it has been thwarted by the loss of top
gear. I have disassembled and carefully measured every part in the
transmission, and everything looks just as it should. Figured I would think a
bit more about the situation before posting this problem for others to offer
their useful comments. [At present, I am leaning towards the possibility that
there is enough play in the camplate that it tips sufficiently to allow the
actuating pin in the upper fork to slip from its slot, jamming the camplate
into the actuating pawl and binding up the shift lever]
#624 looking to my Venom, (because I've read that someone has nearly the
same problem for a MAC and may be this would make some difference) I already
have a breather adaptor on the crankcase with a tube fitted to it going
no-where, but no other tubing on the oil tank than : the tank breather itself
(only 5 or 6 in. long) and the engine feed and return pipes.
If this is a standard arragement, how long shall be the oil tank breather tube,
and the engine breather tube ? or how can I have the tank modified so the
engine breathes into the oil tank ?
#625 Since your oil tank has no other form of breather I think you would be correct
in thinking that you should have a vented cap, and the flooding scenario
suggests that the build-up of heat during sustained high speed operation is
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causing the tank to pressurise and prevent the return of oil to the tank from
the engine. The simple solution would be the vented cap of course, but I don't
think that a hole as big as 1/4" would be necessary and may result in a well
lubricated right leg! Your engine will breathe through the 1/8" diameter hole
that runs through the drive side mainshaft into the primary chaincase via the
channels cut in the inner diameter of the engine sprocket. This system was
found to be inadequate for higher performance engines and was eventually
developed into the alternative system as I described, and incorporated in all
late models, I think from about 1967, but I stand to be corrected on this. My
own Venom is a 1962 model which originally had only the mainshaft type breather
and the oil tank was fitted with a filter chamber as I described earlier, and
only the 1/4" bore tank breather tube from the rear. I have since fitted a
Thruxton spec tank which sits a little further rearward than the original to
give room for the longer inlet tract (or a decent length of velocity stack),
and have modified the crankcases to bring them up to the latest spec. So far
I've retained the original system of breathing into the chaincase as well,
since this must help to lubricate the shock absorber cam, sprocket and primary
chain, but it still suffered from what I considered to be excessive breathing
into the chaincase. Following advice from the good people at Seymours, I've
just had the oil pump overhauled for the first time in the machine's sometimes
hard life and hope that all will now be perfect enough to report soon that the
chaincase remains reasonably dry. We shall see!
Shall be interested to hear what you find on the gearbox front. We happen to be
on common ground here since mine too is dismantled at present for renewal of
the sleeve gear bush in an effort to restore efficient clutch operation. I
sometimes think that we old bike fans would be lost if we weren't tinkering
with bits of machinery!
#626 If your breather arrangement on the crankcase is correct and you are using the
late spec oil tank (or one modified to Keith's spec), the pipes should be as
1.. Breather hose - engine to oil tank (21.375" long x 1/2" bore)
2.. Breather hose - oil tank to rear of machine (27.5" long x 3/8" bore)
#638 While on the subject of oil tanks, I strongly recommend the fitting of the
VOC oil filter kit in place of the original. The cartridge filters are so
much more efficient at straining out contaminants. On early oil tanks it
fits without any modification, on later tanks you need to file away about
1-2 mm of protruding tube. If you do this put the tank cap on and block the
tube off from the inside with a small piece of rag to avoid iron filings in
the oil tank.
Details of the kit can be found here
#639 Problems to translate, what do you mean "to file away 1 - 2 mm of the
protruding tube" ?
#640 A more general question about oil filtering. In disassembling the oil feed
tube on my '50 MAC, I noticed that it did not have the "gauze filter" described
in the owner's manual (it did have a ball check valve which seems redundant,
since there is already one in the crank case). It occurred to me that some
sort of filter would be in order.
In discussing this with some more knowledgeable people, they essentially told
me not to bother, as long as I was vigilant in changing my oil regularly.
There rationale was twofold: i) the tolerances in the pump are rather large by
today's standards, so small particulates will essentially pass through the pump
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anyway, and ii) any filter with even a small pressure drop across it will
prevent the oil pump from doing its job properly, since it is a volume (not
pressure) based system, and will not tolerate significant pressure drops. They
further opined that the gauze filters were suitably porous that they didn't do
an effective job of filtering the fine particulates anyway.
Apparently, the filters under discussion here are meant for later [and
different?] machines. Regardless, should I be pursuing the installation of
some sort of filter on the input line?
#641 On later Velos, the plain hole from which the oil flowed from the filter
chamber back to the oil tank was replaced by a very short piece of tube. The
tube enters the filter chamber and stops the oil filter cartridge from
fitting easily, so it needs to be filed away to allow the filter to fit into
the chamber.
#659 What's the best low-tech method of sealing the poly tubing to the
copper tails of the banjo(etc) connections in the oil system?
#660 Take them to a hydraulic hose or lorry parts company and get them crimped.
#733 I
won't be able to resist having a go on it before taking it apart but feel I
should at least change the engine oil before I run it. I have Silkolene
30's and various modern multigrades. Any thoughts?
#733 Strait 40 at this time of year, in the engine, gearbox and chaincase.
and refill the gearbox as water may have entered. Silkolene is a good
#761 I've got a couple of questions which I hope someone can answer.
The oil filter in the tank has been taken out and an external (RGM) filter
fitted on the return line. Is this a real advantage or not? I'd really
not have the external one on, simply because I don't like the look of it.
it were a real advantage I could (just) live with it. I would have thought
that the original filter is adequate providing oil is changed regularly.
views welcome.
There is a breather from the inside of the timing casing to a stub (3/8
at the top inside of the oil tank. I can't remember this from my last
though it is a long time ago and it seems a reasonable thing to do. The oil
tank also has a stub pipe (1/4 bore) on the inside at the bottom. This has
pipe leading from it. It seems to be a breather with an internal pipe
to the top of the tank. Is it? If it is, why does it come out of the tank
near the bottom? Should it have a pipe on it and if so should it just exit
somewhere convenient or should it be piped to somewhere in particular?
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#762 A few years ago while changing the filter in a BMW twin I found it fit
Velo oil tank quite well, so that's what I use. It's a paper cartridge
filter. All that's needed to fit a Velo is a couple big o-rings or washers
to center it in the bore. Some tanks will need to have the small tube
trimmed back to let the filter slide by. Framm and Purolater market this
filter if you don't feel like frequenting the local Beemer shop
#765 Regarding the additional engine breather. Apparently at certain rpm it
found that crankcase pressure prevented adequate draining of oil from the
rockers / cylinder head. An additional breather was added from the timing
chest, underneath the magneto, to the top of the oil tank. This then vented
via a tube from the froth tower to the rear of the bike. This was
in the mid sixties, but it is an often found modification - my machine
included. I believe prior to this normal crankcase venting was through the
chaincase. A previous owner of my machine even vented the chaincase via a
snazzy little breather tube arranged from the chaincase inspection cover. I
think the small 1/4 bore pipe at the bottom of the tank was a breather
was also used to lubricate the chain (this being blanked off on my
A cartridge conversion is available via the Velo owners club which replaces
the felt filter with a paper cartridge type. This fits in the original
filter tube and is spring mounted which allows oil to bypass the filter if
it becomes blocked.
#766 Reference to previous postings will yield a lot of info on the
breather subject
and in general what Brian says here is correct. However, I can see no
to the breather tube from the chaincase since this is already very free to
breathe due to the huge hole through which the shock absorber spring
and secondly, the 1/4" bore pipe at the bottom of the tank really should
not be
led to the chain in an attempt to lubricate it. This is the tank breather
should vent to atmosphere well away from the chain since the acidic gasses
exude from this pipe will help to cause premature corrosion of the drive
Mine is led along the rear subframe and simply vents to the rear of the
where it can do no damage.
#770 On the oil filters, I wouldn't worry too much about a bypass valve.
it's on the return side the worst that can happen if the filter plugs is
much oil in the sump. Never seen it happen.
#774 I plan to modify my "old fashion" oil
tank to the more recent standard.
The crankcase having been modified by the previous owner, I would like to
"recycle" the oil coming out from the crankcase breather.
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My first series oil tank being already fitted with its own breather outlet,
coming from the froth tower down to the outlet tubing coming off the inside
face of the tank, if possible, I would like to know the exact location and
dimensional information of the additional tubing to be fitted to receive
21.375 in. crankcase breather pipe.
#783 has anybody converted an enginge to the later oil drain
from the timing chest to the bottom of the motor. i think this mod
came in about 1964. it looks like an external rib. i belive you can
do this but you have to plug the crankcase in the bottom of the
timing chest to stop oil draining into the motor internally. i was
going to to this some years ago but hit a problem with clearance
between the motor and the frame, to put a union on the bottom of the
motor was going to foul and i decided not to bother, but having
thinked about it i could come in at an angle and tap the hole and
then screw in a tube much like the later breather tube under the
mag.has anybody tried this ?. it would then be straight forward to
connect to the tube, and then to the bottom of the timing chest.
velocette did some tests and discovered that when the engines were
running, oil was backed up to as much as three quarters of the timing
chest as it was unable to drain into the bottom of the motor fast
enough due to the flywheels stopping the oil going down the internail
drain hole. this was one of the reasons why they did a revision of
the crankcase. you should end up with a better crankcase than the
later ones with this mod because the earlier cases have the restictor
in the oil passage way to stop debris going into the pump and the
later cases do not have it. any feedback is wellcome. regaurding the
later breathing arrangement, i read that people are doing this and
breathing into the oil tank, i hope that when they are putting the
tube under the mag into the timing chest that they are also putting a
hole from the timing chest into the crankcase otherwise it is a
complete waste of time, because with out the hole from the timing
chest to the crankcase the air cannot be expelled. just my two cents
worth. thanks for taking the time to read this. cheers.
#784 I have added the oil drain line to the timing case. I used two 90
1/8" US pipe fittings, one tapped in at the bottom of the timing chest and
the other at the bottom front of the side of the case (thinking the oil
would be lowest at that point while running). This is a tight fit in the
frame as the frame curves near the case at that point (swing arm frame). To
do over again I would put it further back where the frame rails are
as I can't remove the fitting with cases in the bike. A side benefit with
this mod is that with clear tubing I can always see how much oil is in the
sump when sitting. You can just see it in the photo at:
I did not plug the old drain hole figuring it would now function as a
breather between the crank case and timing chest along with several others
holes I added. Wet sumping while running has not been a problem even with
pump spinning 50% faster than stock 2 start (1/4 vs. 1/6 crank speed). I'm
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getting ready to test pumping additional oil to the exhaust rocker box for
cooling which may create a drainback problem, we'll see.
#785 (ref#774) . Weld in a piece of half inch od tube about 1.5 inches long
at the top of the
rear of the oil tank. Make sure it clears the down tube when fitted. For a
better pipe run, you can weld the tube in angled towards the front.
#828 My apologies for taking so long to get back to you on this one.
My oil tank is one which began life as a standard Venom tank and has been
modified to Thruxton spec including relocating the mounting position
to provide clearance for a long velocity stack or inlet manifold, and is
also chamfered on the inner rear corner to clear the rear mudguard, so the
actual position of the breather pipe connections may not be quite where you
would want them on your machine. However, the 21.375" crankcase to oil tank
breather hose is 10mm bore reinforced PVC, pushed on to a 1½" long stub of
fairly thin walled tube which I think is 3/8" ID. Off hand I can't remember
dimensions of the crankcase connection but the hose is a good fit there
The tank connection is welded about ½" from the top of the tank, just
the filter chamber in a position which will clear the frame down tube. The
breather is also relocated about 2" below and 1" to the rear of the engine
breather connection in a position to clear the rear mudguard. This is ¼"
and extends up inside the tank to the top of the froth tower, and has a
of ¼" ID reinforced PVC hose 27½" long venting to atmosphere at the rear of
#899 (re msg#783?) Having done that, throw the tube away! I did that over
40 years ago, and have
never missed it! Then you have permanent peace of mind, at least as far as
blocked return goes
#900 If you dispense with the tube inside the filter, the entire contents
of the
filter chamber will drain back through the oil pump into the crankcase when
engine is stopped. NOT a good idea to remove it.
#902 Entire contents? The whole half cup-full? As I said, I have never
noticed a=
ny deleterious effects whatsoever! Maybe you would if you are one of the
ditionalists who insist on using SAE50 oil, but not with the recommended
##907 And all the crap that has been pumped up into the chamber on the
dirty side of
the filter? I think I'd rather leave that in the filter and not draining
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through the oil pump whatever oil I use!
##908 In USA, and probably in Canada too, the quoted Octane number is
(M+R)/2. Th=
erefore what is 92 octane in USA is probably a close equivalent to 95-96
in UK, and the 97 (R+M)/2 must be around 100 RON or so.
I thought you'd like to know that! It does cause confusion.
#909 If that is correct then North American 97 grade fuel should be the
stuff to use
without a doubt. If Michael has been running on the lower grade option
backing off the ignition timing then this is highly likely to be the cause
his holed piston don't you think?
##911 Both my bikes came without this mystery oil filter tube. Can someone
please spec one out so I cam
make one?
#915 Part number A293/2 is what you want - sorry I can't give you
dimensions without
taking my oil tank to bits! As I remember, it is a piece of alloy tube
which is
a push fit over the LE547 filter cap adapter shoulder below the cross
The OD is just about the same size as the hole in the bottom filter cap and
is long enough to come to about an inch short of the top cap when fitted.
¼" stud runs up inside the tube. It's not unusual for the tube to come off
adapter, perhaps when changing the filter and either thrown away or simply
dropped back on to the stud without being properly located whence of course
will not do the job it was meant to!
#916 Quite right. The top grade should be used in Vipers and Venoms. Lower
s are OK for MACs and MSSs in standard trim, but their use with the higher
Rs will cause pinking and eventually holed pistons. Using the wrong spark
ug can do this too, by causing pre-ignition. NGK B8ES or harder is
for VM etc.
#918 I'd suggest that most debris from the oil is already well
embedded in the filter felt, and any oil which does drain back will do so
slowly that any metallic pieces large enough to cause damage will settle to
bottom of the filter chamber. The 'drain' hole (the cross drilling) is not
the extreme bottom. The oil returning to the sump has to dribble through
.001" clearances in the oil pump, so it will hardly gush! Having
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experienced a
blocked return due to the existence of this tube, and losing all the oil as
result of the return pipe subsequently blowing off, I MUCH prefer to
with the tube and risk a little debris returning from whence it came,
than a complete engine seizure!
By the way, if all the blocked return does is to cause a build up of oil in
crankcase, there is a serious weakness in the oil pump. The pump cannot
at running speed and not pass more oil than could possibly squeeze through
pump clearances. You will therfore get a very high pressure in the return
and excessive wear on the pump drive gear and worm (creating damaging
debris in
the sump!!!).
#919 I always run Sunoco grade 94 (they claim is the highest available in
Is Aviation fuel an option?
#925 The tube is 0.500 od, 6.850 in length made of aluminium. The wall
is approx 37 thou. The tube is a heavy push fit, light press fit over the
fitting at the bottom of the studding; you can clearly see the step it fits
over on the fitting. Bore a piece of ali tube or bar out so that it fits.
For what it's worth I would fit the tube for the following reasons.
1) the filter holds quite a quantity of oil, and this together with the oil
left normally in the bottom of the crankcase may make starting more
2) If you fit the club filter kit (which I recommend you will need it.
3) if it serves no purpose, Veloce would have saved the pennies by not
fitting it
I agree that it is unlikely any debris above a thou will find its way past
the oil pump, I just don't like the thought of all that debris dropping
#926 Personally I wouldn't recommend using Avgas. Although the normal
rating is
100LL (100 Octane Low Lead) my experience with an Aprilia 250 GP bike
demonstrated that this is not a cure all for detonation problems. This
was bought new direct from the factory in '90 for use in the British and
European championships and came with the usual amount of technical
documentation and help that one gets from an Italian factory - not a lot!
Believing that we ought to be running high octane race fuel which was
unobtainable in the UK at the time and since the rules on fuel were being
tightened up, on advice from BP we began running the machine on Super
98 RON pump fuel (BP claimed at the time that their pump average for this
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was 99 RON). Since this was a two-stroke machine we mistakenly believed
the lack of lead shouldn't be a problem. Within a dozen or so laps of
on the first time out we had a holed piston. Consultation with people in
know suggested that perhaps we ought to be running leaded fuel so the next
out we ran a 50/50 mix of 4* leaded fuel and Avgas, a common brew in racing
at the time. This stopped us holing pistons but we continued to have a
amount of detonation erosion on the top of the pistons and the rider always
reported poor carburation whatever jetting settings we ran. I gradually
increased the proportion of Avgas until we were eventually running 100% of
stuff but never completely got rid of the det damage and it appeared that
carburation problem was getting worse. Eventually frustration led me to go
the other extreme and I tried 100% 4* as a last resort and - hey presto! no
more detonation and perfect carburation! This led me to believe that
Avgas is rated at a high octane it is not designed for use at ground level
at several thousand feet up in the air where the oxygen content of the
atmosphere is lower. The "Low Lead" tag is misleading too, in fact Avgas
has a
higher lead content than 4* leaded gasoline.
However, as the regs regarding fuel have changed over the last few years,
of the factories have produced racing machines which are designed to run on
Avgas and have combustion chamber shape and ignition advance curves altered
suit the burn characteristics of the fuel. My conclusion was that in
Avgas was no help in tackling det problems in engines unless those engines
designed for it in the first place. Better to alter the timing to suit the
available fuel, particularly when you can't get Avgas from your everyday
station. What would you do if you went for a touring holiday on the bike have
someone follow with a tanker full of special fuel?
#932 In the USA Sunoco sells a variety of race fuels, their website is There is a dealer close to me that has 110 octane
(R+M/2) leaded, they also offer unleaded up to 104. And leaded up to
117! Also methanol if you are racing speedway or sprint cars.
With a 50/50 mix of the 110 and the 91 octane U/L "premium" sold in
our local gas stations, my VMT starts first kick, no pinking. Since
this bike is not intended for long-distance touring (rather for 100 200 mile rides on Sundays), this works for me. All other Velos in
our garage are timed at 36 - 37 degrees and run 8:1 CR or less.
30 years ago I thought my Venom had a rod knock, took it down to the
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crankshaft looking for a non-existant problem, realized years later
it was pinking.
#934 What about so called octane boosters? Is any one brand
preferred over another?
#936 When my piston "holed" it also bent things in the oil pump making me
that as well as needing now to take the engine apart to clean everything
Would this new filter have saved me?
#938 Unlikely, as the filter is after the pump not before it. What it does
strain out the very fine contaminants that cause wear in the engine.
#940 Octane boosters are a waste of space.
#941 Do it that way and you won't be able to take it apart easily to clean
it when
you do a filter change. The Velo factory guys weren't stupid, their way is
still fairly well thought out most of the time, personally I would leave it
way they intended or replace with the cartridge filter conversion.
#942 Warning! Anything potent enough to raise octane significantly in
small amounts will likely be so poisonous and/or carcinogenic that
you wouldn't want it in your garage, much less toolkit or tankbag.
Remember Dave Allcock...
#1035 On the question of petrol in the UK as an owner of a Lotus elan for
the last 30 years until recently. The Lotus twincam engine with 10.5
c/r & webers carbs, the drop in octane in UK petrol has been a real
problem! in starting & pinking. 95ron & 97 ron is not the same as
the old BS octane figure, that use to be on the British petrol pumps
the MON octane is lower than RON, & LRP has not even got a British
Standard!! The FBHVC lead replacement testing was only carried out on
a Rover A series iron head low compressions engines @ 4 deg advance
for VSR measurements, which is no criteria for a high compression
engine. But in the Lotus world we do know QED with Miller oils had
done engine power tests with QED dynamometer with Millers CVL.
(Competition valve lubricant) on the twin cam. Test showed that it
produced considerable power increase using 95 ron unleaded fuel at
300ml x 20 ltrs further inquires with Miller oils tech dept confirmed
the results that CVL produces a rise of 3 octane & Millers VSP a rise
of 2.
I used VSP in my Lotus for two years before I sold it to great effect
that I was able to advance the ignition back to 12 deg. from 10 deg
which most of us had been running at since the loss of 5 star petrol
in the uk,
I have been using it in the Velocette although the MAC is not a
Performance engine. I think it improves starting? The only problem
with using octane boosting additives is Millers is manganese, Castrol
valvemaster is phosphorous and LRP is generally potassium although
individual oil companies will not confirm this? But what ever you use
you must stick to it as they do not mix, the other unknown factor is
long term corrosion if any? Only time will tell. Which as somebody
has already said, makes Gordon Jennings, thesis on Plugs, a bit old
hat nowdays endoil
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Frame (inc.wheels & tyres)
#21 I found that a set of tires, Avon Speedmaster ribbed front, Roadrunner
rear, lasted 3 thousand miles, period..
#83 Does anyone know the correct tyre pressures for Dunlop TT 100's when
fitted to a Venom?
#84 Modern tyre pressures need higher pressures than those figures
published in 60's and 70's. I have a table of pressures for tyres
which I hope to publish on the technical site soon.
However if my memory serves me well, TT100's are 3.60 X 19 front,
4.10 X 19 rear. That gives pressures of 26 tpi front, 28 tpi rear for
a machine and rider of 580 pounds. This was confirmed by a leading UK
supplier of tyres who indpendantly recogmended 24 and 28
respectively. By the way I run Avon Venoms and Super Venoms on my
Venom at 22psi front 26 psi rear, and they handle perfectly.
#134 I have a 1960 Venom road test that states the top speed is 95mph with 65mph
lights. But with the sidecar on this makes very little difference to us.
Can anyone explain why the forks can be removed with ease but are quite
illegitimate to put back to obtain the correct pressure on the shrouds to
prevent them rattling. Or has anyone learnt the secret.
#136 There is probably some approved method to stop rattles. The hairy method a
few of us use is to run the bike, down a very quiet road with a few bumps
but not too many, with the lower pinch bolts out. Don't brake heavily, it
could be interesting. Stop from time to time to see if that's done the
trick, and when it has, put the pinch bolts back. This is slightly suicidal
and I refuse any legal liability, but it generally works when bouncing up
and down has failed
#138 By the way have you remembered to offset the forks springs to the nearside and include the
rubber washers between the shrouds and springs?.
#144 I start by putting the bottom yoke in the vice. I clean any paint off the
inside of the inside of the fork yoke and grease it. I then put a wedge in
the slots of the lower fork yoke, and check the top spring claw, F262, will
fit easily. I leave the wedge during assembly.
My tools include my version of LET 796, and another device which I can't
identify on the shelf, for holding the damper while screwing the bottom nut.
#90 Avon Roadrunner AM20 90/90H19 front @ 22 psi, Avon Super Venom AM18 100/90V19 rear @
24/26 psi. An added benefit, they even make the bike look faster!!!
#172 I have recently acquired a Venom Clubman which has a very slightly
buckled Front wheel rim.
In addition, the front brake is grabbing and sending a vibration
through the forks which feels like the wheel brake drum has become
slightly oval.
Please could anyone advise the best course of action? Is it possible
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to skim the drake drum, and to straighten a slighly bent rim, or do I
need new components.
Also if anyone has any contacts who have experience of such work, I
woild be very gratful to receive your feedback.
Finally, I am considering at the same time opgrading the front brake
to a twin leading shoe one. Again, any help in sourcing one would be
#173 Is the rim actually dented or merely out of true? A bit of careful and patient
spoke tuning will correct the latter. If it is dented, it must be disassembled
and straightened. Don't let some sharp talk you out of it, as Dunlop alloy rims
are very desirable items.
Personally, I have had little luck skimming Velo drums when not spoked to a
rim. If you can find a lathe that will accept a complete wheel, it is worth a
try. True the rim first.
#226 I have a Borrani WM2/1.85-19/36/Record RM-01-4354 Rim laced to a
Venom full width hub. Does anybody know if a replacement is available
that matches or nearly matches this Borrani
#227 I am assuming you have a flanged Borrani aluminium rim. Currently I have three Velos that
sport alloy rims including Dunlops Akronts, UK made ali rims and have had Borranis in the past.
Borranis are recognised by those in the know as being the best.
Even if you find a second hand Borrani you need to ensure that the dimple pattern, spoke hole angle
and diameters are suitable for lacing to a Velo hub. Currently in the UK to my knowledge there are
two replacement flanged alloy rims available. Unless you look at them closely they look similar to
Borranis or Dunlops. However they are not as well finished, so if you buy one check in the area of the
weld for the quality of finished. Secondly one of these rims has very crude looking dimples, so take
Further details on the rims can be found via the link below.
#229 This is a pretty specific request for info; does anyone know if there is
a replacement taper-roller steering head bearing for KTT's mk 1 and 8? I
just pulled the forks from my mk 8 and the cups are, understandably at 64
years, a little dimpled. As I'm also ready to put my mk 1 back together, I
thought it a good idea to change this out as well. Anyone have any
experience here? Paul d'O
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230 There was an article in UK Fishtail 298 on using taper rollers in a MKII KSS that maybe of use
#232 May I suggest taking the original bearing
races to your local bearing supplier. Try Yellow
pages. If you get the ID right and the OD can be
cylindrically ground to fit. Might be worth a shot
#278 I am ashamed to ask to the member. it is non Velo things.
But I am interesting to know what kind of none original Tele fork fit on the
Velo swing arm frame? and how do they fit ? How handling effected?
I am thinking the machine for novice racing purpose as well as road (
250cc). I would prefer pre-63 folk and English one. ( timing cover said
"MADE IN ENGLAND" is it?),no alternation to the frame ( in case I will
replace it back later) and more widely available than Velo fork with rebound
once I heard that Roadholder would fit, but I realized there were several
type of Roadholders. I gave it up because not knowing what I was looking
#279 You could try a set of Metal Profile forks. These were British, available for
many years without any major changes and were commonly used as an aftermarket
upgrade by racers of the period. You might find some by scouring the
autojumbles or spares advertisements.
#294 I've two sets of suspension units,both incomplete,both slightly
different.The most salvageable have annular spring supports fixed(?)
to the damper unit:the other set has an indent approx halfway up the
damper,presumably for collets.Anybody recognize this description?If
so please where can identification/spares be obtained?
#296 Woodhead Munroes measure 6.5 cm OD and have an annular ring at the bottom.
#300 Does any one know what pressure I should pump the air forks up to on
my '48 MAC I have been told it is virtualy impossible to obtain seals
for them here in U.K is this true.
#301Do not over pressure it. Just a few strokes of the hand pump until the
forks are nearly fully extended. Then with your weight on the saddle,
release some air out of the Kilner valve until the edge of the shroud
coincides with a small dimple, or perhaps a little before if you want a bit
more ground clearance.
The dimple was originally painted with a red dot.
#359 My newly acquired Venom is less than stable at the back end,
especially with a pillion and there is smear of oil on the left
shock absorber. The shocks are the early Woodhead-Monroe type and I
would like to retain the appearance. There is a web site for a place
in the USA that will rebuild these shocks using new parts and
retaining the appearance but I don't want to send them that far, not
least because I'm enjoying riding the bike and don't want it laid up
for both weeks of the British summer!
Hagon have Girling pattern shocks for Venoms available but they have
no parts that are compatible with the "long fat shroud" look of the
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Is there anywhere in the UK that can repair or replace W-M shocks for
Or should I bin them and fit Hagons? (The bike is mainly for riding
and isn't totally original anyway - VR cases etc.)
#363 You could try contacting Martin in the attached Q & A
#404 I have managed to put a dent in the chrome petrol tank of my 1960
Venom. It is about 2cm across and 2-3 mm deep.
Does anyone know anybody who can repair this without having to get it
beaten out rechromed and repainted. The depression (apart from mine)
is about 10cm from the filler cap. I have heard of people repairing
car panels that have minor damage without needing to respray but not
a chrome petrol tank.
#416 Hi - this is Brian (with the original leaky dampers) chipping in
again as there seems to be a dearth of hard info on this topic. I've
solved my immediate problem by buying a new pair of shocks from NJB (reasonable at £78 + post). The bottom eyes of my
original shocks had 2 tapered rubber bushes, the NJB shocks come
withn a parallel bush and shim washers to line them up. They have
transformed the ride and are highly recommended - they look identical
to Girlings.
Now I've got my old shocks off I can see that the dampers are way
past simply refilling. The tube has rusted where the bike was stood
for years and the seal has gone. The options seem to be somehow hard
chrome the damper and replace the seal or get new damper units for
the old covers. I don't think I'll bother as I'm happy with the bike
as it is now but I can't see how drilling/refilling alone can be
#463 For my 1952 MAC rigid documentation say front and rear tyre both 3.25 x 19.
My front tyre is Metzeler Perfect ME 11 - 3.25 x 19.
My rear tyre is Avon Roadrunner 90/90 H 19 - 3.60 H 19.
I was informed that it could be difficult to get the rear tyre homologated in
Germany. Is there any information / documentation available about my rear tyre
size being eligible?.
#463 For my 1952 MAC rigid documentation say front and rear tyre both 3.25 x 19.
My front tyre is Metzeler Perfect ME 11 - 3.25 x 19.
My rear tyre is Avon Roadrunner 90/90 H 19 - 3.60 H 19.
I was informed that it could be difficult to get the rear tyre homologated in
Germany. Is there any information / documentation available about my rear tyre
size being eligible?.
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#471 From the German represantation of Avon Tyres I got confirmation that the "old"
tyre size 3.00/3.25 corresponds with the actual specification 3.60 (or 90/90 in
So they have sent a certificate to me saying that the tyre 3.60-19 is the right
application for a Velocette MAC..
#487 My 1948 MAC has Dowty air filled forks fitted,working fine till last
weekend run of 110 miles,they now lose pressure completely over 4 day
period,anyone else had this problem and is it curable?I have refilled
each leg with clean oil and hope this may help,what grade oil is
best straight 20 grade reccomended originaly.
#524 I hope changing oil has rectified your Dowtys. I had a pair that I was going
to fit to my 1948 MAC. I dragged them around three house moves in twenty
years, leaking oil continuously! I looked to fit new seals but these are now
virtually impossible to get hold of. Carol who does all the UK Velo auto
jumbles had some seals for Dowtys, but I don’t know if she has any left.
Another alternative is that Sammy Miller does/did spring conversion kits for
Dowtys <> if you
get desperate..
#528 Thanks for reply the oil change has made things worse,forks
lose pressure in 10 hour period now,are they likely to "collapse"
suddenly whilst being ridden?Could you let me know how to contact
Carol to see if she has any seals,cheers Dave..
#537 The last number I had for Carol Kear was 01242 239432.
#547 I was wondering what would be some appropriate tires for my Venom.I'm
looking for something a little more modern than what was originally
#548 You can't get any better than a good set of TT 100's they were good enough
for the TT they will give you everything you want with the venom.
#549 I'm a Dunlop fan for the moderns, but on the Velos there is nothing better than
Avons, Speedmaster II front and Roadrunner Universal on the back. They are
made in the old molds but of modern compounds. They wear out very quickly
(<3000 miles on my Venom), but give better grip than the Dunlops on 2MAC. They
also tend to crack sooner. If longevity in your climate is a concern you might
want to stick to the Dunlops.
I went AM20/18 Super Venom on the Thruxton, but will change them out for the
set listed above at the very first opportunity. They may look more old
fashioned but give fantastic grip.
If you have a racing license you might check Race Tire Services to see if they
still have any Sport Elite fronts, K591 100/90V19 race compound, Dunlop made
them for 883 racing. They are really sticky and would work on front or (IMHO)
rear. They fit a 2.15 rim.
#551 Well, here's my two cents on the tire issue. I've always used TT100's
(Dunlop K81) on my Thruxton, 3.25" x 19" front, 4.10" x 19" rear. I've never
had a slide, and the deep ground chamfer on my exhaust pipe and silencer say
the TT 100's are indeed good enough.
On my Viper clubman I use an Avon SM mk II front (3.25x19) and Avon
Roadrunner rear (4.10x19), althought I'm not sure they make that pattern
anymore (same one as on the Geoff Dodkin bike on the cover of Reg Hide's 'All
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Years Vm/Vr/Vmt Service Sheets' etc). This combo looks more 'vintage'. They
seem to work well, but the ribbed SM front does indeed wear out in 3k miles,
as Tom mentioned. They are very 'giving', ie not a hard tire, whereas the
TT100 is fairly stiff by comparison. It would take someone on a smooth
track to tell the virtues of one over the other.
On my mkIV KTT I use the same combo as above (SM/Roadrunner), but using a
3.60x19 on the rear. I've had the front wheel wash out on indifferent
surfaces. Girder forks? Tires? Dunno. But the tire wear is waaay over to
the sidewall, where you wouldn't think it would reach, all the way to those
little teeny ribs, which must reflect the 'give' of the sidewall. If you
were to lean the bike over to the limit of wear on the tire while stationary,
the saddle would have been ground away a little!
#552 More to add to the debate…
#592 Just "lost" the battery retaining strap on my '61 Venom this morning
on the way to work.Found the old-type black battery cover on my left
foot at a set of traffic lights! Retraced my route with special
emphasis on the gutter - found the retaining strap but no sign at all
of the bolt. Question - what is the size and thread type of the bolt??
#593 The bolt is a 2BA thread, I think about an inch and a half long. There is a
trick whick might prevent future losses - fit a nut to the bolt before running
it through the threaded trunnion, as you tighten the bolt it will trap the nut
between the two strap ends and act as a lock nut, and if the bolt should come
loose after this the nut will usually help to retain the bolt and plain
trunnion in the strap.
#653 1960 Venom clubman,
I am using Dunlop K81 (TT 100) tyres front and rear.
What are the sugested tyre pressures????(solo)
#654 There has been a previous thread on the subject
#658 I dismantled the (girder) forks the other day - an interesting
exercise! - but I can't seem to free the bottom of the spring from
the forks, anybody know if it's screwed/clamped on or is it just
being held on by rust? Forks are marked "The Webb" if that helps!
#664 The bottom of the spring is screwed onto a flattened thread: tap it a few
times, lubricate it and then unscrew.....they can be tight.
684 I have managed to find a source of Dowty Fork Seals at a much lower
price than other suppliers charge,that is if you can find a
supplier,I can get them through the hydraulics company I work for email me on [email protected]
#879 Here's a question for the group... where can I get tapered tube for
heavyweight Webb's to replace my damaged ones. And how were they
made originally, was it in one complete tube from the top lug down
or two? (ie. four tubes per set or eight tubes per set).
#882 i belive that percival and webb of dudley west midlands
are still going strong. i think they still make girder forks and do
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overhauls and repairs. i think they are a offshoot of autocycle which
is run by chris williams.
#889 Try :- Ray Daniels
144 Station Road
B33 8BT
Phone :- 0121 789 8900
#953 What is the
width of the 1929 Mk 1 KTT rear drum? Front? Does the rear hub have
a bolt on sprocket? What are the lengths of the top & bottom fork links?
What are the lengths of the top & bottom fork links? The length of brake
rod & diameter & thread? And
finally... was the front rim 21" (WM1) x 36 holes? Was the rear rim
(WM2) 19" x 40 holes?
#954 The rear brake drum and sprocket are one piece
The top links are 3.25" between centres
The bottom links are 3.5" between centres
The carb in 29 would have been a brass Amal (pre mono block type)
The front rim is 21" WM1 36 holes
The rear is 21" WM1 40 holes
Which brake rod are you referring to? - the rear is .25" with a BSF thread;
front isn't (I'll have to check if that's the one you're after.)
The rear brake drum has 1" linings for the KTT, as far as the width of the
overall goes I'll have to do a sketch.
#1033 my 500 velo has a set of ajs or matchless front forks, which i think
are the same, i just wondered why? can any body tell me if there is
any benifit to them.
#1034 You don't give a description of them, but later
model Matchless forks were both compression and
rebound damped with a rebound spring that kept them
from "topping out". The Thruxton and Scrambler Velos
had rebound damping, but for off road the Matchless
forks were a better bet. Norton (I'm in trouble now)
put the Matchless forks on their P-11 desert racer
instead of their Roadholders.endfra
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#1 I have a Viper which has no battery connected - it has 6V electrics
and a Lucas E3L Dynamo. It has a LUCAS regulator - on the mudguard although not taken this apart to see if std or dsomething like JG
conversion underneath/
How do I know whether to use positive or negative earth - some
manuals say negative aome positive - any tests before connection?
If i get it wrong and run the bike - what damage if wrong polarity could I be looking at?
If the battery is connected and the lights turned on - I assume
ammeter would show '-' when lights on if right way round - if
connected wrongly '+'? is this feasible?
Anyone know a source ok KIF magdrives - are these fibre or steel?.
#2 You've worked out the best quick test - checking which way the
ammeter swings. However, if you have an electronic regulator then it
can indeed be damaged if you connect up the battery the wrong way
round. So either look into the "Lucas" regulator can or simply
disconnect it for the test.
Another way, if the ammeter had been disconnected, is to see which
direction the dynamo motors in; but that takes longer and isn't 100%
reliable. Or the colour coding of the wires will indicate what it was
originally.....but an owner may have reversed everything.
It depends if you have an autoadvance unit or manual. If manual, it
is a simple steel wheel. The Owners Club can supply top-quality
drilled and lightened versions of these. If autoadvance it originally
was fibre, that could strip, so steel conversions are available.
I believe Dave Lindsley has everything for K1F magnetos, he's at
0706 365838
196 Pilsworth Road,
#23 . I also converted the shaft of my distributor of my 1969 VMT to ball bearings some ten years ago.
Plus the fitting of Boyer electronic ignition and 12Volts by JG unit and careful stroboscobing, I have
not touched the ignition setting since 10 years and 15000 miles.
It is clear to fit a sealed bearing towards the CB room of course.
If you use a Boyer (pre digital) ignition, be careful with the coils. I have a collection of outburned coils.
Especially the thin 12V ones ast only 1000 miles. Ernie Brandsen gave then the advise to fit the
genuine thick Lucas 6 V coil with a Norton Commando ballast resistor in series. Till today it does the
trick !
#27 I've had no luck with electronic systems, probably not sufficiently
convinced to persist long enough to clear up all the problems. Means going
to 12v which I have on only one of my Velos.
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With my ball-bearing conversion, I couldn't find an oil seal which fits, so
the outer bearing is sealed on one side..
#88 am in the process of installing a Boyer
ignition on my 1970 Venom Clubman, keeping the bike at 6V. I'm
wondering if there are any other electrical mods I should make at the
same time to improve reliability. Should I replace the original
Lucas voltage regulator? How about the coil? Does static ignition
timing work well on these bikes, or should I strobe it?
Also, I'm assuming this bike is positive ground, since all the pretty
red wires go to the frame :)
#89 You can stay at 6v, but if you intend riding much at night, why not look at
alternators? There are two on the market at least, my preference going to
the one which looks most like the old dynamo. The dynamo style one comes
with control gear, as does the Lucas alternator version.
You can use a cheap voltmeter, a useful bike tool anyway, to check polarity.
Personally, I have never had much luck with electronic ignition systems, and
still use points. As the Velo does not have a fixed mark for strobing, the
result you get depends on your skill setting it up. Which also applies to
static timing.
#91 I have my doubts if you will succeed with 6V and a Boyer ignition. I have a Boyer on my Thruxton
since 13 years, but, as far as I am aware of, it only works with 12V.
I converted the dynamo with a JG unit to 12V and the system works reliable. If you convert to 12V
here is one good tip (from Ernie Brandsen, the electronic wizzard himself) : Use the old 6V ignition
coil with a Norton Commando ballast resistor in series.
#92 I did purchase a 6v Boyer unit,
so theoretically it should work. It's turning out to be a bit more
involved than I initially thought, since I need to replace the coil
(the original coil is 2 ohms, and the unit requires one in the 5 ohm
range. I'm also going to switch to a solid state voltage regulator
while I'm at it
#93 Most electronic devices (semiconductors) need roughly 4.5 VDC minimum for function. In any
wiring system there is a voltage drop across each of the numerous connections. When you include
the effects of time and weather it is very unlikely that your Boyer will have sufficient voltage to operate
reliably in a 6V system. This is also one reason that 6V lights tend to look dim, even if the power
rating (wattage) is the same.
OTOH, you could solder up all the connectors - but this makes repair a bit difficult!
I agree with Herr Patek, the JG has been 100% reliable on both my 60W Lucas (Venom) and 36W
Miller (MAC) dynamos. The Venom has 30,000 miles and 12 years on this setup. I cannot think of
any good reason to stick with 6V. Also, both bikes have magnetos, and after towing a couple of dead
Velos equipped with coil or electronic ignitions I would not use anything else.
#95 When my dynamo burnt out I was toying with the idea of fitting an alternator or converting the
dynamo to 12V. The Alton alternator looks more like a dynamo than the Criterion but I preferred the
bike to at least look original. I tend not to ride the Venom at night as the VFR seems much more
suitable for this.
In the end I had the dynamo rebuilt (cheaper than an alternator) and replaced the KTec (part of the
reason why the dynamo burnt out) with a 6V JG regulator. The only modification with this was to
convert from a positive earth to a negative earth.
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Another useful modification was to replace the dynamo V belt with the owners club tooth belt, which
requires less tension and puts less strain on the dynamo bearings.
I have also had my magneto overhauled (extensively) and it seems to give a hefty spark, so I am also
in favour of points
#97 I got a dynamo rewound to 12v, and the fellow who did it wasn't happy. He
claims there is physically not enougfh room to put in as much copper wire as
should properly be done. He also says there will probably be some inferior
rewinding jobs around. May be that he's a perfectionist.
As long as a modification is easily reversible, I have nothing against it.
#98 Electronic regulators (and 12 volt conversions) have been around for a
couple of decades now. The conversion requires no rewiring or other
mucking about with the dynamo (assuming it is in good shape to start).
There were some problems with very early JG units, but they are quite
reliable now.
If you run electrical accesories such as heated clothing, better buy
an alternator. My vest draws 60W by itself, which would not leave
anything for the lights. Up to now I've toughed it out, but advancing age will
soon force me to install an Alton.
Procedure: (tip o'the hat to FT and Ed G.):
1. Examine machine for magneto. If found, proceed with step 2. If
not, purchase 12V coil or (thanx Johann) Commando ballast resistor. I am not
sure if you need a 12V condenser, wouldn't hurt.
2. Purchase 12V JG electronic regulator, plus suitable battery and
bulbs. The horn will be fine unless you live in Cairo.
2. Polarize dynamo per red book or instructions packaged with
3. Install above listed items. VERY IMPORTANT - install a main fuse
on the battery (10A should do it). Ride away.
On my Venom the ammeter shows charge at anything over 40 mph in top.
The MAC (even with it's wimpy little 36W Miller) performs similarly. The only
dynamo problems I have had with either was when the screws
holding the mounting plate backed out (Lucas). Oh, and the brushes
stick once in a while.
Concering cosmetics, the JG is small and silver in color. It's not
visible under the seat of the Venom, and on ZUMAC I painted it black.
This has not kept ZUMAC from earning a trophy every time I have
shown it.
I use a full sized Yuasa motorcycle battery, wrapped in self-stick
pebble-grained black vinyl film made by 3M. It is used on auto
bodies and a good paint shop should be able to get it. You have to
be within 10 feet - and know what to look for - to notice it. Others
have cut open an old black-case 6v battery and placed a small 12V one
inside. I saw a reference to a metal cover somewhere, too. And the
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sealed type batteries are black already, if a bit dear. There is one
on my Honda XR650L - I think it's called a Dominator in the UK. Personally, I
like having lots of battery; the Venom has been used
for campsite illumination during late night work sessions on VOCNA
Summer Rallys.
This is the best reason for sticking to a mag - battery condition
doesn't affect engine operation. When it finally becomes so
discharged and sulphated that the dynamo field windings can't
function (no charge even when revved), buy a new one. Plus, if you
leave an ignition coil powered up for very long without airflow for
cooling it can explode and spray tar everywhere. Happened to a
friend's Clubman...
#99 I am very surprised to hear that Boyer offers now a 6V electronic ignition unit. Those Boyer guys
are excellent in technical respects, but quite bad in marketing their products. Who knows the exact
difference between a MkIII and a microdigital unit ?
Instead of running their identical advert in all magazines, they should describe their products closer.
The only draw back I always had with all Boyer units were the coils. An A65 twin worked perfectly with
two 12V coils parallel, the Commando only with two 6V coils in series. The 12V converted Thruxton,
blew about six 12V coils of different makes on the most uncomfortable places (single repair lane of
motorway on top of a bridge with no escape lane, big fun !) till my desperate call to Ernie Brandsen
revealed the secret of using the original 6V coil with that mysterious Norton Commando ballast
resistor in series. Why not telling the customer in advance ?
I agree with Tom Ross (hi, how is Mobby Dick?) that the most reliable ignition is a magneto, and in
this case a BTH. Once you have a rewound armature and everything checked over, you should have
no problems. On my Venom I use a manual TT BTH magnbeto with a steel geared Lucas ATD and
this offers the best of both worlds. Reliable and smooth tickover, and the possibility to adjust at full
revs when the engine pinks a bit. I have 8 old bikes and long winter months (lay up periods) and
compulsory daylight riding. So I converted all magneto ignited ones to battery less systems, because I
dont want to buy several batteries each year. I short cutted the cutouts and adjusted the voltage to
about 7V at full revs. The light switch stays permanently on, and from a little over 1500 revs, I have
lights which can be seen, though this does not say, that I see anything at night with a 6V Miller 30W
system, for instance.
One word to the praise of the JG units. It seems they work perfect on Velos, but we tried four (4) on
three different Goldstars, with the effect of boiling batteries, burned bulbs and 3 exploding dynamos !!!
A very expensive try ! It appeared it has something to do with the high revs of the magdynos on the
Goldies (the dynamo rotates with 10500 rpm at full revs). We all reverted to conventional mechanical
regulators then.
Fitting an electronic ignition to an original coil equipped Velo is the easiest (and cheapest) way to
overcome the sloppy distributor spindle. For the Boyer unit it does not matter if there is a bit up and
down clearance on the spindle once the rotor stays between the poles. But you always need to watch
the healthy state of your battery, be it 6 or 12V.
#100 To all of you considering of fitting either a JG or Ktec voltage regluator unit :
There is one major snag with all those electronic regulators. Once your battery is completely flat
(after winter lay up) or because the idiot riding it forgot to switch off the lights, the battery is not
charged at all after a restart (only possible with a magneto), no matter how hard you rev the engine.
We experienced that there must be sufficient voltage in the battery left to get the whole system
working again. At least halve charged !
No manufactor of the those units state this affair in their descriptions !
A mechanical regulator instead also provides a charge to a completely flat battery
#101 I disagree that a mechanical regulator will charge a fully discharged battery.
The field coils of the dynamo must be energized first before the dynamo can
function. However, the mechanical regulator will function at a slightly lower
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battery voltage; the threshold voltage required by the semiconductors in a JG
(about 0.7 VDC) must be overcome. This means that a battery too flat to fire
up a JG might still work with a mechanical regulator. I remain unconvinced
about no battery at all.
#102 I understand that the magneto system is much simpler, and when properly set-up is very
reliable, but, it seems to me that if the battery is kept up by regular running, and the coil(s) are of good
quality, and considering that millions of vehicles of all types use coil/battery ignition systems, if the
quality of the Boyer system is good, what would the problem be, aside from the dynamo being
required for double duty, ignition and lights? My Mac has the 12V JG unit in place with a B-B ignition
system installed in a K1F body by Dave Smith and seems to work just fine, though it has not had a
great deal of usage as yet,
#103 I recently converted my '56 MAC to 12V lights and ignition. It required rewiring the Miller
Dynamo to 12V, using the excellent JG Electronic Regulator, but I left the old regulator box on the
dynamo to look "right". I got a Boyer Bransden 12 V electronic ignition unit very nicely installed in a
K1F Lucas Mag body with new shaft and sealed bearings by Dave Smith Classic Motorcycles here in
the US, along with the required coil, a small German made unit that seems a good one. I got
a 10amph battery that is a bit small but works well. Except for the required extra wiring to be properly
installed, and retiming according to the clear instructions, that's it. The mag on my MAC needed
rebuilding, so I opted for the Electronic ignition and she starts up 2nd kick every time and often on the
first if I do my bit.
Of course, you could just convert to 12V lighting and make sure the 6v mag is is good shape for
ignition. My lower back is pretty bad, so any guarantee of less kicking over is happily appreciated
#107 I think there is a way of using the magneto points in conjunction with a
coil. This is a distant memory from the 60's and 70's.
Can anyone advise?
#108 I have tried JG's K-Tecs, dynamos with little success. I also have a
Criterion type alternator conversion. In my opinion the best solution is the
Alton. It is easily fitted, well engineered, has great performance and is
aesthetically pleasing. I have had mine for 3 years, I did have a strange
mechanical failure outside the warranty period but they replaced the unit,
just for the cost of the postage.
Its performance is superb - and even when you point out that you have an
alternator fitted, the most common comment is "I can't see one. I have
uploaded the information files in the file storage area of the group site,
within the "Electrics" folder.(Dai Gibbison)
#109 in nearly 15,000 miles of Velo rallies here in
the US, the most common breakdown I've seen is due to a non-standard coil
ignition failing, due to either a flat battery or fried electronics, followed
by fibre gears stripping on Lucas mag's
#110 Both my Velos have the
original magnetos, and I have had good performance from them. Indeed, the
Venom's 35 y.o. K1F needed some work a couple of years ago - not the standard
capacitor-and-remagnetizing, just new bearings and insulators. It was then
demonstrated to produce a 1/4" spark when turned by hand. It's a shame that
the Works couldn't get mags by the late 60's - I read somewhere that toward the
end they would send a runner with cash for one or two at a time. A coil system
is relatively "cheap and cheerful."
The problems I have seen with coil and B-B type systems have usually
resulted not from faulty product but with the installation and
maintenance. Bad connections, batteries shorted from vibration, and
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not installing proper fuses result in being stranded. Obviously this is not a
concern with a mag. Most roads where I ride are very lonely, often lack mobile
phone coverage, and vultures circle overhead. And I am not eager to win
VOCNA's booby prize - the highly non-coveted Crock of Sh## Trophy awarded to
the Chase Truck Queen on our Summer Ride.
I should point out that, unlike some areas, daytime lighting for old bikes is
not a requirement in my home state (California). All you need is a brake
light. Also, I have several bikes and am constantly charging flat batteries.
Being able to hop on the Venom and ride off regardless is a real pleasure. As
long as the battery doesn't fall off onto my foot, as happened with a mate's
Velo once!
Also, the added current draw from a coil or B-B will raise the rpm
required for a dynamo to produce a charge. This could be marginal on
a 36W Miller on a slow revver like a MAC.
#112 By the way, are there any sources for good used or rebuilt Lucas K1F mags, or is this a cry in
the dark. Even though I have electronic ignition and 12V sparks for the lights, I'd like to have a
standard mag in reserve,
#115 I ride the MACt three times a week, for at least 20-50 miles per trip. The Miller is converted to
12V so in effect it now puts out 72 volts, though that is a technical rating. It seems to charge up quite
well between 4-6 volts cruising along, but I will always keep an eye on it,.
#117 The Alton was designed by a French Vincent owner, Hervé Hamon; For those who don't know
Alton, it simply bolts on, in place of the Miller/Lucas dynamo and is belt
driven as per the original. If you wish later to go back to the standard
instrument, this is simple, other than the rest of the bike being 12v
#118 I 'phoned Paul Hamon, who is Hervé's brother
He does not recommend toothed belts, and the control gear is sold with the
He has an Email which I don't have yet, but which I'll pass on when I get
#121 All the details on the Alton have been uploaded to the files section of the Velocette e group. Try
this link.
#124 Unfortunately you cannot use your JG with an alternator, as it was designed to regulate a
dynamo. There are sources within the UK that sell reconditioned KIFs but I have no experience of the
quality, so I could not recommend a supplier. If it’s just names and contact details you want I can
provide these
#131 Dai gave the link to take you to his electrical files, where there is the
Email address and other interesting information, including prices etc.
[email protected] is Paul Hamon's address, but have a look at Dai's
files which will give you all you want to know. It comes with control gear.
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#157 Would it be possible to get the names and contact info regarding the Lucas K1F mags we talked
#159 Sorry for the delay in getting back to you. Below you are the telephone numbers of UK suppliers
of reconditioned mags, I have not used them so I can make no recommendations. Some may only
provide exchanges.
Dave Lindsley +44 (0) 1706 365838
FTW +44 (0) 114233 6269
Independent ignition supplies +44 (0) 1237 475986
Dynamos only P Dunn +44 (0) 1782 856839
#165 I am sure many people are famuliar with Dave Lindsley. There was an
article on him in FT 310 which describes his attention to detail.
He has reconditioned both my mag and my dynamo and I am very pleased
with the results.
Independent Ignition supplies have a website at
#182 Looking at page 3 of "Tips" on I read
the following:
"1. When setting the timing on Miller systems, bring the flywheel into
alignment of TDC by setting the hole in the flywheel central to the hole in
the mounting back plate. Adjust the cam unit to just opening the points, in
a clockwise direction, with the bob weights in a FULLY OPEN POSITION. i.e.
fully advanced. This is not clearly stated in the workshop manual."
(End of quote)
Surely this will give a large amount of retard at starting, and will only
advance the spark to TDC at full revs?
I have assiduously studied all the manuals and documentation I can find, and
nowhere do they give a degree figure for the fully advanced setting for the
LE Miller set. They all tell me to set TDC with the holes referred to in
alignment (TDC) and fit the ATD with the points just opening. This would be
fully retarded at TDC, and presumably the degree of advance is set by the
operation of the bob weights, of an amount not specified.
I will do a little experimenting/measuring to find just how much the ATD
does effect an advance, but nowhere have I been able to find a figure
#211 Just finishing the installation of the B-B Mark 3 6v ignition system
on my Velo Venom Clubman. I have two questions:
1) Is there any disadvantage to putting the controller unit inside
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the battery box? Lots of room in there, but it would mean running
wires about 18" long to the coil. The B-B instructions say to mount
the box near the coil.
2) It's been suggested to me that the stock coil may not work, since
it's only 2.1 ohms, and a 5 ohm coil would work better. The only 5
ohm coil I can find is a 12v unit. Is there anything inherently 12
or 6v about a coil, or is the resistance the only differentiator? In
other words, what happens if you use a 12v coil in a 6v system.
I'm beginning to think life would have been easier if I just bit the
bullet and converted to 12v, but I'm too far down this road to turn
back now.
#220 Boyer do sukpply a 12 volt
coil and if you phone their help line after 4 pm I have always found
them very helpful
#269 My Venom is fitted with a BTH mag, which never missed a beat in 30 years. Then the
condenser failed, and I had the mag rebuild in England. The electrician told modern condensers are
not designed for this use, and could fail more or less quickly. And of course it happened few month
and 500 miles later, away from home.
I'm sure this is a common problem. How do you solve it ?
There where an article some time ago in FT about Dave Lindsley. Do you think he can give me a long
term solution ?
Thank you for you help.
Olivier (France)
#337 Having had some mildly worrying times on dark country lanes due to fading Miller glimmer, I
have been wondering if the grass would be greener with uprated electrics.
I have enough bits to change to a Lucas 6 volt late model 60W dynamo and appropriate regulator as
the BMS book suggests Or....
The JG unit has been around for a long time but am I being over cautious in mistrusting electronic
boxes on vibrating British bikes?
I am not keen on the Criterion alternator conversion, preferring the appearance of the dynamo, so is
the Alton unit the (expensive) answer? Is its accompanying regulator just another electronic box?
I have been a VOC member for two years so I haven't got the relevant fishtail articles on Alton and
2CV alternator conversions.
Can anybody give me their real life opinions of these conversions and their reliability on wet winter
#.338 Re alternators etc. These comments are based on my own experience.
I ran my Thruxton for many years with a J.G. conversation with no
reliability problems. The drawback was despite a first class
dynamo, with the headlights on the battery would eventually drain
and the lights. (output checked by suppliers of dynamo)
I decidedduring a bike rebuild to convert to electronic ignition,
(Boyer). I had used it in the past and was impressed with its
performance and advantages. Since the slow running problems with the
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J>G> an alternator conversation was I thought necessary. I was
impressed with the unobtrusive looks of the Alton but thought the
Criterion was a known, proven and made in Britain. I ventured on the
side of looks,but was unable to make contact with the manufactures of
the Alton so the Criterion was purchased and fitted some years ago.
Initially I used a Zener diode and rectifier with no problems. I
later fitted a Boyer power box with does away with the Zener and
other ancillaries, this was several years ago and todate has given no
problems. Electrics are not my strong point but find wiring a
electronic igniton system and the control box as simple as wiring a
three pin plug.
#341 I have run an Alton alternator now for about 4 years and have had no
problems. It does come with a hefty fully encased regulator unit and
the strap will have to be changed for a more substantial type. Their
is a strong magnetic pull compared to a dynamo I also run it with a
club supplied tooth belt.The only critcism if any is the vents on the
body (water ingestion maybe on the exposed posistion on a Velo).
Moreover, as it was designed for the Vincent some maybe supplied with
a parallel keyed shaft for a magdyno not a taper a la Velo.They are
expensive but are a clever bit of design also by the time you've had
a dynamo overhauled bought a new electronic regulator you're half way
to buying the Alton with 150 watts.
#342 I have run an Alton alternator now for about 4 years and have had no
problems. It does come with a hefty fully encased regulator unit and
the strap will have to be changed for a more substantial type. Their
is a strong magnetic pull compared to a dynamo I also run it with a
club supplied tooth belt.The only critcism if any is the vents on the
body (water ingestion maybe on the exposed posistion on a Velo).
Moreover, as it was designed for the Vincent some maybe supplied with
a parallel keyed shaft for a magdyno not a taper a la Velo.They are
expensive but are a clever bit of design also by the time you've had
a dynamo overhauled bought a new electronic regulator you're half way
to buying the Alton with 150 watts.
#344 I purchased an Alton direct from the manufacturer in France about six years ago. My views are
as follows;
The Alton is simple to fit; the most difficult task is removing the front engine plate to get at the1/4 BSW
bolt that holds the dynamo strap on. You need to do this to fit the substantial slotted strap that comes
with the unit. The rest of the installation took about 30 minutes.
#346 Don't know if people are generally aware of this, but a modern
alternative self-generating magneto ignition system is being
developed by Rex Caunt Racing using the BT-H trade mark. The results
can be seen at or by following
the links from
Rex makes ignition systems for classic racers which are considered to
be one of the best. The magnetos are not cheap, estimated price on
his web site is £500, but it might be worth it for a reliable system
and a weight saving of over 3/4lb over a Lucas K1F. Base mounted
units already in production for AJS/Matchless etc are available with
a choice of 2 advance curves built in so I would guess that they can
be run without an ATD - another positive point for those who want to
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run a tacho drive from the timing cover but don't want the hassle of
manual advance.
#347 I have heard from a "reliable" source that the Altons are hard on
bearings, and have a lifespan of 10,000 miles or so. How many miles
do you have on your second unit?
Even if true this would probably not matter to most owners, but for a
machine used regularly it could be a concern. I should also point
out that my Venom has needed new bearings in both dynamo and mag
during its 33,000 mile history. The screws backed out of the dynamo
end housing, apparently a common complaint.
#348 I have completed just over three thousand miles with the Alton, and unless it stops raining soon
I won’t be adding many more miles this year!
A friend has a Criterion and has had to change the sealed bearings in that after approximately 3000
#381 My recently acquired '61 Venom Clubman has original Miller electrics all working v well! But - it has a Cibie head lamp unit that has no
provision for a pilot/parking light. It has a current MOT but my
local testing station is telling me that I need to have a pilot
light. The Miller light switch clearlyy has pilot and main beam
positions. Any thoughts/advice??
#382 My recently acquired '61 Venom Clubman has original Miller electrics all working v well! But - it has a Cibie head lamp unit that has no
provision for a pilot/parking light. It has a current MOT but my
local testing station is telling me that I need to have a pilot
light. The Miller light switch clearlyy has pilot and main beam
positions. Any thoughts/advice??
#383 Change the sealed beam unit. Remember the pilot bulb assembly.
Contact R F Seymour Ltd. 01 844 217 277. They will sort it
#384 I guess the real question is - is it a legal requirement to have a pilot light ? If it is, how come my
Velo came with a valid MOT??
#385 The Cibie light unit makes a big difference to your headlight at night. I assume you have the
concave lens that was fitted in the seventies.
I have a Cibie fitted with a pilot, but they are now have convex glass. You should be able to get them
from M & P in the UK cost GBP 33. M & P part number 525 334.
#386 As far as I can ascertain the pilot light is obligatory on all vehicles fitted
with lighting systems - but some testers are more lenient than others as we all
#395 Seymours advise me that if no pilot light is
fitted then, so far as the MoT is concerned that's fine i.e. if there's no
pilot light in the light unit it doesn't have to work!!. But if a pilot light
is fitted then it must be in working order.
#396 Sorry guys, I do believe that Seymours are wrong in their interpretation of the
regulations. As far as I can make out the pilot (or front position light as it
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is termed in the regs) is the obligatory part of the lighting system on all
vehicles fitted with lights. The relevant parts of the MOT testers manual are
as follows. These are taken from the general testers manual, but the Motorcycle
testers manual is the same in essence.
This inspection applies to: all vehicles except those used only during the
hours of daylight, and which are not fitted with any front or rear position
lamps or have such lamps permanently disconnected, painted over or masked. If
no front or rear position lamps are fitted to a vehicle, there is no legal
requirement to fit any other lamp.
Obligatory front position lamps (side lamps)
lamps required by regulations to be fitted to a vehicle to indicate its
presence and width when viewed from the front.
They must show a steady white light to the front, or a yellow light, if
incorporated in a headlamp which emits yellow light.
The light must be visible from a reasonable distance.
Method of Inspection
1. check that two side lamps and two rear lamps are fitted to the vehicle, one
of each on each side.
2. check the presence, condition, security and operation of the switch.
Reason for rejection
1. An obligatory lamp missing
2. A missing, insecure or faulty switch.
As I said before, different testers might interpret the regulations
differently, but as I see it the key statement here is "If no front or rear
position lamps are fitted to a vehicle, there is no legal requirement to fit
any other lamp." Headlamps are covered by a separate part of the regulations.
When the regs go on to say that a vehicle should fail the test if an
"Obligatory front position lamp (side lamp)" is missing, on "all vehicles
except those used only during the hours of daylight", I think this is fairly
clear cut.
Pete C.
#397 Pete - that is very helpful but I now have another opinion from an MOT station
that confirms Seymours view! The reasoning is as follows:- My Miller switch has
two positions in which the headlamp bulb lights but only one of the positions
dips. Therefore the non-dippable headlamp constitutes the "front position
light" as required by the regs. Apparently the regs say nothing about the front
position light being a separate bulb/unit etc from the Headlight. Therfore a
light unit with no separate pilot is absoultely OK as long as the headlight
bulb is switchable from two independent positions - in one case it is the
front psoition light and in the second it is the headlight.I guess the easy
answer is to take the bike to Seymours - or a like-minded testing station - to
get the MOT - when do we ever use the pilot light anyway??
#398 If you have converted to 12 volts I recommend buying a Hella H4
headlamp lens and specify the one fitted to early Minis. This had a
sidelight. Also Ring do one the same.
#399 In your case you will be absolutely correct, and this may be a way round the
problem, but I don't think that was the way the switch was intended to be wired
up originally. I think you will find that the first position was intended to be
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wired to the pilot light, but somewhere in the machine's past it has been wired
directly to the dip filament in the headlight instead. In this configuration
the dip beam does in fact become the pilot light, since it is independant of
the dip switch and satisfies all the criteria of the test, albeit a bit grey in
terms of being a separate light bulb. When you move the switch on to the
headlight position the power is routed through the dip switch before going to
the headlight, so you then of course satisfy the criteria for the headlight.
What you lose however, is the failsafe position that should the dip filament
fail (a very likely scenario!) you do not have the pilot light to enable other
road users to see you without being blinded by your high beam. I agree that we
seldom if ever use the pilot light through choice, after all what chance have
you of seeing anything beyond the glow on the front mudguard, but the general
principle is that, as stated in the regs, "The light must be visible from a
reasonable distance," indicating that the idea is not to see, but to be seen..
#419 Miller lights in good condition are impossible to get hold of. If you are
lucky you may be able to get a NOS Lucas, the correct item should have the
words “motorcycle” and “700 Headlamp” embossed in the glass. If you want to
use a halogen bulb (recommended) try your local Enfield India dealer who
should sell them to fit (they may even sell Lucas light units). The bulb is
not the same as the modern halogen bulbs.
Alternatively buy a Cebie light, which are excellent and no one will notice.
You can do what I did on my MSS to keep it original; bought a light unit,
smashed and removed the original glass and used silicon sealant to bond the
existing Miller glass into the unit..
#530 Could you please tell me where I could purchase a 6 volt Boyer Ignition
system for a 1961 Venom Clubman?
#532 I bought mine from Dave Smith Classics.
#553 want to get a few basic spares that do not seem to be
available through the velocette spares.
1. 24w/24w 6v SBC double filament bifocal. (pre-focussed type)
Lucas168 or Philips 6722 are not listed any more.emailed Grove
Classics 2 weeks ago but got no reply's, the bulb in the Miller
head light is a Stanley 6v 18w18w SBC which is a bit of an odd one?
#554 I fit a 6v halogen bulb which will fit strait in to the Miller / Lucas
headlight unit. They are made for Indian Enfield’s and I usually pick them
up at auto jumbles for £5. Try calling +44 (0)1454 323434 who sell them for
£7. I would phone Grove classics rather than e mail, when you will receive
excellent service.
#557 A 30w main and 24w low beam is available from Walridge Motors
([email protected]). It is their P/N BULB 312. Lots in stock $5.67ea
Canadian. I do notice that my supposedly optimally functioning Miller dynamo
still does not keep up with the 24w low beam at low rpms. Thus the 18w Stanley
bulb that David Gibson describes is an interesting possibility. David does not
provide a wattage rating for the halogen bulb he describes.
#652 Spent part of the w'end investigating a low / zero charging rate on
my '61 clubmanised Venom. The Miller ammeter was showing a very
intermittent or zero charge. Dynamo drive is a vee belt and no sign
of slipping. I discovered that although I have a Miller headlamp
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switch and ammeter I have a Lucas dynamo - I thought that these did
not come into use until '65?
I couldn't make out any model number on the casing - but I assume it
must be an E3L? If this is correct can I get 12 volts from it?
I discovered a Lucas RB108 regulator fixed under the seat but the
bonded rubber mountings had parted and hence the regulator was held
in place only by the wiring. Does anybody have any experience / tips
for repairing the bonded rubber mountings ? I have done a quick fix
of taping the regulator body to the mounting bracket but clearly this
is not a long term solution!
The various tinkerings seem to have solved the charging problem - a
nice steady 7 - 8 amps all the way to work this morning.
#656 Rubber mounts normally go. Answer - Super glue
#674 I've just had a magneto overhaul and refitted it and done all the
business with TDC finders and degree discs. My problem is with
refitting the auto advance mechanism. It came off fine, the bolt
loosening and tightening as it drew off the taper just like it says
in the manual. Putting it back on, the fibre gear meshes perfectly
and the bolt screws on but goes solid about 3/8" before the bolt head
buts against the mechanism leaving the horseshoe washer and the round
plate that locates on the 2 little pins totally loose. I took the mag
off about 3 months ago and I've never messed with an auto advance
before so it may be that there is something else under the bolt head
I've forgotten. I also wonder if the auto extraction (can't get my
head around how that works) in reverse means the bolt goes tight
early and then loosens but I'm reluctant to apply too much force
without asking first. I can't see how I could have put the mag on
wrong. Any thoughts welcome!
#675 Forget about the Mag.
With the ATD in your hand / on the bench, screw the bolt
in until it slops about. Your then past the self extract thread
and can get on with the fitting.
#678 your advice was sound and the ATD is on and the timing
A couple of lessons I've learnt which may be of use to other ATD
virgins: on manual advance mags I've tended to hold the gear or
sprocket on the taper by finger pressure whilst tightening - if you
try that with an ATD you push the ATD body too far in ahead of the
bolt so the mag thread and the extractor thread can both engage
locking everything up. Basically refitting the ATD and setting the
timing are 2 distinct operations, my main mistake was trying to do
both together, best to get the ATD on first and then set the timing.
#688 Wholeheartedly Agree. Dave Lindsley converted mine thus and, I
think,even used
the original cam ring with a bit of deft grinding. Never gave a moments
trouble since. I used to find that the fibre gear would strip if you cogged
down for a steep hill or to overtake. Sadly the bike is no longer in one
piece. Starting was vastly improved too.
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#689 There is a gent in the midlands who will take your ATD unit, remove
the fibre
pinion and cast it into the bin for you, then replace said item with a
beautifully machined and lightened steel pinion which will solve all the
shedding problems and still retain the advantages of an automatic timing
device. Drop me a mail and I'll put you on to him.
#692 That man is John Hales, who can be contacted on +44 (1509)
813507. His price now is around £60
#709 Anyway I now have an early Venom and am considering
upgrading to electronic ignition.
My question - does anyone know where I can get a waisted 3/16 box
spanner to remove the magneto
#712 if you are such a heathen (like I am) as to fit electronic
ignition, why not go all the way and just fit an allen headed bolt, it
life oh so simple. It's fine if you are not regularly taking it off, (then
stud would obviously be better - so you don't wear the hole in the
#713 Fit a BSA "long magneto nut" and solve the problems.
Autocycle Engineering sell them at £4.99.
#724 If you have ignition trouble, make a two foot stick with a small damp
attached to the end and also a wire between the damp sponge and the other
of the wire (grounded) with a 12 volt neon lamp somewhere in series.
Start the bike and slowly wipe the HT lead from pickup to spark plug cover.
Any flashing of the neon lamp indicates a crack or leak and the whole
assembly should be replaced and reevaluated.
#743 i have just accuried a 12 volt 110 watt criterion
alternator which comes with zenner diode and heat sink. the bike it
came off used the mk one venom clubam/ mss/ viper type battery
platform which had a 12 volt 14 amp hour on it. i plan to put it on
my bike which has a mk 2 toolbox come battery holder. < same as
thruxton > the problem i have is that the battery which goes inside
it is quite small, alot less than a 14 amp hour. i am a bit concerned
that the alternator might overcharge the battery with dire results.
should i look to relocate the battery and fit a decent amp hour size.
any feedback on this wellcome.
#751 I was led a merry dance by a carb spitting problem at kickstart/low
The culprit turned out to be the ( peripheral ) slip ring in my manual BTH
magneto; there was a section missing! Presumably, at higher revs the points
operating arm jumped the gap.
#768 A tip for other electrical know-nothings like myself.
I've a very pretty, obviously re-conditioned,model of
one of these which I was considering setting up on the
bench to see what joy I could get from it.
However, along with the stampings E3LM-LO 6v etc.,came
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an arrow pointing in the exact opposite direction to
what I needed.
A quick pnone call to Dave Lindsley(see prev.msgs)set
my mind at rest.
His first comment was that the whole caboodle was a
re-con job ,and that the laminated case was from
another model,but it would be perfectly O.K.
To check(on bikes),join 'F' and 'D' contacts
together,run a wire from here to the pos. terminal of
6v battery.Run a wire from neg. term.of batt. to the
case of the dynamo and the dynamo should run as a
motor in the correct direction.
If it doesn't,just reverse the brushes(with wires).
#778I have just fitted an electronic ignition on starting, the bike it
charging. I have sent the dynamo for repair and I am informed that it is
burnt out due to the electronic ignition and it has been suggested that I
back to Magneto. Have you any thoughts on the subject please, also any
thoughts on converting dynamo from 6v to 12v while it is in for repair.
#779 IMHO, I don't see how the ignition module could "burn out" the dynamo
(generator). Those are big wires in there. The only way I know a
generator could "burn out" is through a massive short circuit, that
heats up the armature and the solder melts and is thrown out. The
ignition module only draws a couple of amps. You should have some
seriously melted wiring if you had a short of that magnitude. BTW, I
would convert to 12V if you can. Much more efficient.
#780 The Boyer ignition module draws less than a tenth of an amp, it's
the coil that uses two or three, same as a regular coil/points
setup. I'm with George, it takes a dead short to burn out a dynamo.
I have had excellent results from electronic voltage regulators made
by "JG", even the little 36 watt Miller on our '56 MAC maintains a
charge at any speed over 40 mph in top, with lights on. We have them
also on Zuma's 1950 MAC, and my Venom. These regulators "trick" the
dynamo into producing 12V by raising the cutout voltage.
Although the '56 has a Boyer, I still prefer magnetos 'cause I hate
the sight of all those wires! Simple is best. But I would look for
another specialist for advice re your dynamo and ignition bits.
#788 it dawned on me that I had made a foolish mistake
recently in claiming that I had traced starting/spitting problems to the
fact that a section was missing from the cam on my manual BTH magneto. Of
course the cam is steel and easily inspected. It was the brass HT pick-up
ring that was found to have a section missing.
#792 If the alternator/zener is operating properly, the battery will not
overcharge no matter what size it is.
On the other hand use the largest battery that wll fit and use a sealed one
is even better.
Podtronics makes
full wave bridge
limits and there
volts,the actual
a good alternator cum regulator that should do better than
plus a zener diode. Keep in mind that Zeners come in all
are manufacturing tolerances, even if the Zener says 14
limiting voltage can vary by a few tenths. The state of
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battery will depend on the type of riding you do ( daytime, nighttime, fast
and long, city trips, etc.).
Many prblems can be traced to negligence of not keeping the battery topped
up. That's why I suggest a maintenance free type.
#797 As soon as I'd sent the e-mail earlier I had a thought and explored
the insides
of the "RB108" regulator. All is not what it seemed! Mounted inside is a
solid state 12v voltage regulator made by TEB Technology. This still
explain the dynamo marked Lucas E3LM-LO, 6v and running in the opposite
direction to that marked on it. The system is positive earth if that is
#806 I have added a copy of an excellent article explaining, how and why to
uprate your dynamo to 12 volts to the files are on the group site.
#808 Here are three short answers to your electrical system questions.
1. The dynamo can operate in either direction, this is determined by
connections and polarization, as described in Dai's articles and the
literature that accompanies the electronic regulators.
2. Opearation at 12V reduces losses in the wires and connectors,
giving brighter lighting. Sealed headlamp units are also commonly
available in 12V.
3. The original Lucas regulators shatter at the mountings (takes
about 10k miles). The various electronic ones do not.
Also, the contact points in the Lucas reg can stick, burn out, etc.
etc. You could adjust a Lucas reg to give 12V if you wanted to, but
most owners take the easy path and fit an electronic one.
#818 The insides of an RB108 are essentially the same as an MRC2. Someone
replaced the original guts and replaced it with some solid state thing.
Best solution, use a Podtronics from Kizer.
#821 The lighting system I'm building up on my MAC is
The voltage regulator I have, which looks in good
nick,has a flat base with two bolt holes at 3 5/8"
centres.It's not obvious to me where it's meant to be
#823 that one is usually somewhere under the seat.
Often bolted to the rear mudguard.
Recommend you throw away the 'innards' and install a
new electronic regulator into the box.
I'm told that the Podtronic device is 'The Best'.
#834 The original position for the regulator was on top of the dynamo, it
moved in 1958 to the top of the rear mudguard. You can just about see it in
this photo.
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#840 I've got a 1951 MAC, with a new 6 volt battery and bulbs - but it
won't charge.
I'd prefer to hide the regulator unit in the old Miller case above
the dynamo as it would be too visible sited on the mudguard,
(separate seats)
I've got a 12 volt JG unit (which won't fit in the Miller case) and
also the converted 60 watt dynamo which worked perfectly last time I
used them on my Venom - about 17 years ago.
Is it best to use the 12 volt system although it would mean buying a
new battery, bulbs and headlight(and horn?).
I've heard of K.Tec and now I hear about Pod Tronic.
From real experiences, which is best and where do I contact the
various companies and how much do they cost?
#843 The Lucas MCR2 voltage regulator I have looks in good
condition, but as indicated in recent messages it
seems like a 'Podtronics' item maybe a better
long-term bet.
So,where can these items be found in the U.K., and at
roughly what cost?
#845 SRM Engineering have recently started importing
the Podtronics regulator.
SRM Engineering
Unit 22 Glanyrafon Industrial Estate,
SY23 3JQ
#849 For anyone else interested in similar
technology,here's the reply I received from
[email protected] :'We have choices of 6v & 12v conversion
Podtronics,both available in pos. or neg. earth.
Units are wired in same manner (FADE) as standard
regulators & so are simple to install;comes with
diagrams anyway.Units are(here I guess they're talking
about the model I asked about) £64.88(incl p&p and
#867 I am uniquely qualified to give you advice on dynamos an voltage
I have tried to get them working on three Velos and failed every time.
Having spoken to others 12v dynamos are better than 6v, but they need to
at greater speed to maintain a charge.
Anyway here's my input
K-Tec - cheap aprox GBP25, available from lots of classic bike dealers.
never got one to work and there is absolutely no technical support.
JG - more expensive larger, and if you buy it from the right place you
should get technical support. Still need a knack to get them working.
I have heard lots of good things about the support and product made by CMES
in Bristol, telephone number +44 (0) 1454 323434, but I have never used
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#870 What I'm looking for is an original wiring diagram for a 6v system
(Lucas).I presume there must have been such a diagram issued with the
Owner's Handbook.
#978 By the way does anybody have a horn for sale or know where I can get
#986 Try Taff Isaac at Swansea. He will advise you on which horn you should
He prefers it if you have an old one that he can restore for you but does
have some that he has already restored.
His EMail address is [email protected]
#1032 does any body have any info on 2cv alternators for velos i think
there are 2 sorts, the early one has no built in rectifier where as
the later one has a built in rectifier.if any body has done this mod
have they a wireing diagram.iwould like to have negative earth if
thisis possible.
#1073 just to say there is at least one UK supplier offering an
alternative/improvement to the std Velo dynamo strap - its not me
and I dont own any shares in the company either !! but they do work
well - I have one on each of my VM's to secure the Alton on one,
dynamo on the other.
Also - might seem obvious - but Ive found this bolt can be a b*gger
to remove after long use (esp if previous owner loctites it
in....!!) so its worth a blob of grease when fitting. I do quite
high miles (hence the Alton)and have had no trouble with anything
coming loose here.endele
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Cables & controls (incl.brakes)
#39 The Scitsu electronic tacho
#44 Bob Jolly makes replica mk VIII magnesium hubs/brake plates/shoes (yes these
are mag too), in Australia, they cost about $800 us/ea, depending on exchange
#172 I have recently acquired a Venom Clubman which has a very slightly
buckled Front wheel rim.
In addition, the front brake is grabbing and sending a vibration
through the forks which feels like the wheel brake drum has become
slightly oval.
Please could anyone advise the best course of action? Is it possible
to skim the drake drum, and to straighten a slighly bent rim, or do I
need new components.
Also if anyone has any contacts who have experience of such work, I
woild be very gratful to receive your feedback.
Finally, I am considering at the same time opgrading the front brake
to a twin leading shoe one. Again, any help in sourcing one would be
#174 Before you buy a TLS, make sure the drum is round and the linings well matched.
Give the original brake a fair trial. I changed my Venom over to a Dodkin/Velo
TLS in 1988. It has never been much more powerful than the original, and is
utterly useless when backing down a ramp! Perhaps the racers find it more fade
resistant, but don't assume that it will let you do stoppies.
#175 Grove Classics sell the iron half of the front hub for a Venom/Viper approx
?150, if you need tp replace it.
#737 Velo. VM6333E had been abandoned in swampy Louisiana after the speedo
had done its magic on yanking the handlebars to full right lock - it didn't
take a forensic scientist to figure out the cause of its loss of favor with
the original owner
#739 I'm intrigued by this common reference to the speedo
cable somehow becoming wrapped around some other
component.There's even a part in the VSL list which
seems to be designed to prevent this occurence.
I haven't run my being-rebuilt bike yet,but I can't
visualise how this situation would arise.
Are we talking rear wheel drive,single sided hub or
I'd be grateful if someone could describe in simple
terms the cause & the remedy of this problem,
#740 This can only occur on machines with QD rear hubs, and rear wheel
driven speedo
(which is just about all of them unfortunately).
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The cable runs past the hub on the way to the speedo that is ususally
off centre on the handlebars, right?
One day, one of the cap nuts from the QD hub works itself loose, right.
time later, just as you're peaking out in third gear exiting a sweeping
hand bend, the nut decides to exit the sleeve in the hub, right?
Instead of whizzing out and disappearing without consequence, as the tube
resides in is in the top arc of its travel or the bottom arc of its travel,
instead it decides to poke its head out just as it passes the speedo cable,
It jams and
axle, there
force being
on the back
as the cap nut attempts to coil the cable outer around the rear
is an immense and unplanned tension in the whole speedo cable,
transmitted right up to the point where the cable is anchored,
of your offset handlebar mounted speedometer, right?
Now simple high school physics comes into play - turning moment = force x
length of lever arm. Basically the whole plot takes an unexpected turn to
left or right (depending on which side the speedo is mounted).
Hence the sad tales of these hapless riders, such as the former owner of
PD'O Endurance in Louisiana.
The solutions?
A dab of loctite in each cap nut on assembly, and/or
A push in plastic or rubber plug in the open end of the 3 tubes in the rear
hub, and/or
Mount your speedo directly over the centreline of the steering head (not
practical), and/or
Leave your speedo cable and your brake levers at home and attain some
cornering speeds!!
#742 John is nearly correct, actually the problem only exists for full
width hubs, the older "cotton reel" hubs don't trap the cap nuts
("acorn nuts" here in the US) so they are not a problem.
#744 Re Speedo cable causing problems, I mounted a holding
clamp matching that for the tacho cable on the other
side of the under tank strap. This I made tight on
the cable and only tight enough on the tank for the
strap to perform its original function. Theory was
that if the cable started to pull, the clamp would
twist and give a few seconds vital warning that
something was not quite right.
Obvious solution is to never leave home without first
checking your nuts.
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#817 Mike Fotherby at Grove Classic had half a dozen scrambler brake drums
a few
months ago - they may be all gone now but worth a try. He also had some
#959 I've got
to the fitting of the speedo.
It's a Smiths 3" Chronometric & looks in v. good order apart from the
alloy spigot which carries the thread for the speedo cable.This has
been cross-threaded at some stage and may not retain the cable nut(I
haven't got a cable yet).
Does anyone have any good dodges to avoid an expensive solution,or at
least know what thread is used on this item?
#982 I noticed some of the newer cables are a very tight fit so you might
find they
will work for you when you try your new cable.
#984 An unholy but effective dodge is to hacksaw through the cable nut end,
across the
threaded section, in an "X" fashion and fit a small hose clamp over this
You then slip the cable nut over the alloy spigot threads and tighten
the hose clamp
until it engages what's left of the threads. You then can carefully run
it up snug and finish
tightening up the hose clamp to lock it in place. Properly placed, the
clamp screw will
not even be visible.
#1001 Every screw in your smiths speedometer and the gearbox
on the back of a Shadow clock is Metric.
#1002 You are correct in saying that the screws on the Smiths Chronometric
instruments are metric, and also that the two screws that hold the
into the case are an unusual thread, but the size you give is incorrect.
are in fact M5 x 0.75, not 4.8mm diameter. I have tried without success to
source these from every possible supplier, including the current owners of
Smiths rights - Speedograph Richfield in Nottingham. Beware of ordering
screws from SR - they will supply plain ordinary 2BA screws and charge an
unbelievably extortionate price for the privilege of supplying the wrong
I can only report them as being one of the most unhelpful companies I have
had the misfortune to deal with! The good news for those who want to
manufacture their own screws is that taps and dies are listed as available
the Unithread web site ( At £11.70 each for taps and
for dies they are quite expensive, but that's the price you pay for
The correct thread for the cable connection is M12 x 1.0, not ½" BSC x 26
hence your sloppiness, .
Apparently this is because the original Smiths instrument company started
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in Germany before coming to the UK between the wars, so is not quite as
as most people believe!
#1012 , I have just checked with Johnson's the thread is M12 X
1.0 at the speedo end, on the rear drive end it is 1/2 BSC X 26 tpi -endcab
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Chains/Belts & Chaincase
#20 The only thing I want to do now on the MAC, aside from regular proper maintainance is to find a
relatively decent cure for the primary case leakage, which is pretty massive, even after a new seal
was put on. May resort to black silicon sealer.
#25 Most pin type p/chaincases distort finally, so you'll hit this problem with
second-hand cases. I wonder if belt primary drive might not be the solution,
for Velo singles in general.
#28 I've been let down on
the side of the road on a Velo have been primary chains, and both times it
was my fault. The second was trying to run an open case using spray chain
lube, when I lost the oil drain plug on a long ride. Au revoir to chain and
clutch chainwheel both
#31 I was pondering that very thought recently, but though I have seen belt drive units for several of
the more popular parallel twins, nothing for anything so esoteric as a Velo single..
#34 There are two manufactures of belt drives for Velocettes one is by a guy called John Watson
telephone +44 (0)1768 898599, the other is Kevin Thurston telephone +44(0)1525 404699 – both I
have seen, but not used and look well engineered.
#71 I recently fitted a beltdrive cum clutch kit onto my Venom.
As the space inside the primary case is very crammed, a bit of machining of the pulleys was required
to get the required clerances. But otherwise the kit was of unusual high tech quality and fitted straight
forward and the back up help from the manufactor was more than excellent.
Contact John Watson
at [email protected]
Clutch action is better and sharper, and neutral can be found at standstill too.
But do not expect a complete dry primary case. I recognised oil still collecting in it as the crankcase
blows always a bit into the p.c.c. and also some oil from the sleeve gear bush dribbles in it.
I fitted the belt kit because I got tired of cleaning the rear wheel and the garage floor after a fast blast.
I assume the Mac case and clutch is similar to the Venom, but Mr. Watson will know upon these
#133 I've been in touch with Dave Smith of Dave Smith Classic Motorcycles, in Illinois, at
[email protected] and he handles the John Watson belt primary drive system. He is going to get
back to me on my MAC, regarding pricing, because there is little call for this system on the MAC,
mostly the Venom, and I would need a different ratio compared to the Venom, of course. Supposedly
a good quality unit with no major obstacles to installation besides replacing the clutch plates as the
new basket will have friction material as produced, so new plates would help guarantee proper
#135 A word on belt primary drives. As we all know, the mainshaft breathes some
oil into the primary chaincase. But neither the belt primary drive, nor the
dynamo/alternator belt drive really appreciate oil. The primary chaincase
also stops oil from getting at the generator drive. This should be borne in
#137 Most of these primary belt kits come with a complete new clutch. A Velo
clutch will work dry, or wet, but not both ways in alternance..
From experience, the best pressed-metal primary chaincases don't keep oil
well enough, Velocette or other. The same chain, inside a good, oiltight
alloy chaincase gives no great problems. Years ago, I met somebody who had
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cast up an inner Velo primary chaincase out of alloy, but retained the
pressed steel outer. I meant to follow this up, but for some reason didn't.
#139 Glad you brought this up. I have wondered how the generator/alternator v-belt is kept from
slipping with the engine breathing oil mist into the primary case. The belt primary drive I am thinking of
is of the notched tooth variety, and some oil shouldn't affect it too much, especially as these new
plastic/metal core belts don't stretch basically, keeping potential slippage to an absolute minimum.
#140 I guess the cast alloy back half of the primary would keep it somewhat more leak
proof holding normal warpage over time to a minimum. Was this a pin or band type case?
You see, this is one of the things I love about owning this dear old MAC. While I can appreciate
wanting to keep these fine machines absolutely pristine, it is most enjoyable to figure out practical
ways to improve on a good basic design from an earlier time, while keeping the overall feel and
"character". I plan on coming to the Spring Opener of the VOCNA, and plan to ride the several
hundred miles there, alone if needs be, but with another member if possible. More enjoyable and
perhaps handy in case of an oopage of some sort. I expect my MAC to behave in an exemplary
manner, i.e. to get me there, enjoy the rally, and get me within 1 mile of home before tossing
something out the exhaust.
I did find out recently what drippy mess it makes to overfill the Primary case with a less then
perfect felt wiper seal in place over the clutch. 2 1/2 ozs. of oil just didn't seem enough, but, there you
#143 I've seen some weird systems with standard chaincases. One, probably
practical but not too pretty, was to weld a "blister" down the bottom of the
chaincase, to increase the capacity. Another guy put his engine breather
into the chaincase, not the oil tank.
Some schools of thought say to take the engine breather, the one under the
mag, straight out the back of the bike. This, they claim, avoids re-cycling
sulphur-laden oil back to the engine. This breather can be retro fitted.
Stay around long enough, you'll hear everything from the brilliant to the
dangerous in mods. As you say, if there is a real need, probably something
can be done nowadays. Somebody over here says to take the alloy tube out the
centre of the filter. The purpose of this tube, as fitted by Velocette, is
to stop the oil in the filter going into the crankcase when the motor is
stopped, and the Velo attitude seems to me correct. Never assume you know
better than Hall Green: they were pretty practical fellows.
#143 I'm still on primary chains, but I've noticed basically three schools of
thought on primary belts. Original chaincase, with the newer narrow belt,
which presumably means the mainshaft breather oil wanders about inside the
chaincase unless there are some holes somewhere behind. A home-made belt
cover, where it is hard to know just what is going on, or nothing at all.
We raced a Venom with no primary chaincase, just some foam strapped to the
frame under the ESA to keep oil off the track. It was a while ago and I
don't remember clearly, but the quantities of oil coming out were not
massive, and we didn't have a generator drive. Could be it isn't a big
problem. I had a Venom Club, and from time to time, possibly connected with
bore wear and engine speed, it spat out considerable quantities of oil via
the engine/oil tank breather. A friend, more thorough than I, believed on
his similar Club it was the oil frothing too much and thought he'd pinned it
down to a certain make of oil- we're talking of 25 years ago. The only
result was I checked engine oil, as a reflex, every time I stopped.
The alloy rear half of primary chaincase was a pin type. He'd beefed up the
flange on the inner but did say that for a sand casting, his inner was
pretty thin. With a bit of imagination, it would be possible to fit the
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outer half of the primary chaincase only with a belt drive, which would trap
the mainshaft breather oil, and look more "classic". 25 years or so ago,
somebody in California I think made a complete alloy primary chaincase but
it was noticeable to say the least. Mechanically, probably a lot better
#147 In [email protected], "Bruce McNair" <[email protected]> wrote:
... 25 years or so ago,
> somebody in California I think made a complete alloy primary chaincase but
> it was noticeable to say the least. Mechanically, probably a lot better.
> Bruce
The patterns to said item were in my possession up to a few years ago. I was
unable to find a foundry to complete a set (and was unwilling to try myself a
la John Britten) so they went back to Olav Hassel. They were originally made by
Bob Strode of Washington State for a Venom Special road racer and included an
outboard swingarm trunnion support as part of the casting. The trunnion was an
inch longer to fit the case. Another friend had the finished bike until
I think Olav had one set made, but his latest creations (a Metisse and a racing
rigid MAC) had modified original items. Between the casting and machine work it
became a lot of effort to reduce the minor oil loss from the pressed steel
case. Never rode the Strode bike, so I can't offer an opinion re handling.
ps Translation, please, Mr. McNair - by "pin fixing" do you mean screw-type
#148 Yes, pin type is the same as screw type cases. Don't know why, but, there it is.
#149 I'm interested in the idea of a primary belt drive as most of my time is spent trying to keep the oil
in the chaincase or at least off the garage floor.
One thing that has always worried me even in the standard chaincase with the small amount of oil in
it, is the lubrication of the clutch ball race assembly.
Having just replaced one it is not the cheapest item in the clutch
#150 Yes, lubrication is marginal as designed. The result of Britain's use of
roundabouts instead of stoplights? Many owners change the ball bearings for
straight rollers; one can file the cage to suit. This has been successful for
many. The increased contact area seems to compensate for the rollers skidding.
For a more direct solution, I found a tip in an old FT that specified an oil
slot, cut horizontally in the "thrust cup" (C29/26) just above the ball race. I
used an abrasive cutoff wheel in a Dremel tool. The slot is about 1/16" wide by
1/2" long, cut from the clutch side, and slopes down toward the bearing when
viewed in cross section. This has improved oiling so that I am still using the
original ball race, now with 30K miles on it. Thanks to Joe Keys.
If/when I change to belt drive on the Venom I will probably change to rollers
(and keep the slot). The oil from the crankshaft breather should be enough in
the original primary case to reach the bearing. And of course I "never" sit at
a stop with the clutch in...or follow stop-and-go traffic up Pikes Peak...
#151 I was actually referring to the large clutch ballrace assembly C26AS that is an interference fit in
the chainwheel assembly although the same problem would also exist for the clutch thrust bearing if
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there was no oil in the chaincase, as you point out. I have converted my clutch thrust bearing
assembly to rollers also.
#168 I just fitted a Watson belt drive kit onto my Venom Clubman. I use it within the original primary
chaincase. The reason for fitting it was not a clutch problem, it was only the habit of oil spreading on
the left side of the bike and accumulating in the flanged alloy rear rim after prolonged high speed
outings. I got bored of cleaning the bike from oil.
Now I expected no oil loss as none is in the case. But bad news. The engine breathes out enough oil,
that the case slowly fills up with oil again which finds its way out of the case after a certain milage.
Question : How can a garter seal be fitted into the drive side crank case ? It seems there is not
enough meat in the case to give a good seating. I have a "top hat" steel insert in the drive side case
plus a parallel roller bearing conversion. The breather hole in the crankshaft is filled with Araldite. The
engine cases are converted to the VMT type breather system. As I see it, the seal must run on the
boss of the (machined) gearbox sprocket, on which the pulley is bolted on. Is this a very thin seal ?
Would the oil not breath also between sprocket and shaft ?
Would scavenging be improved if that restricting "filter plug" is replaced by a normal plug ?
This reply addresses several emails I received about the belt drive,
garter seal and shielded gearbox bearing and engine breathers.
Hi Tom.
Saw Steve Leonard in the Island in January at the MMCC annual dinner
and will pass on your good wishes when I go over in August for the Manx.
I am trying to persuade John Watson to join this website so that he
can be contact anybody interested in his belt drive.
His E.mail address is [email protected] The belt in
his road going conversion is unaffected by oil.
There is no number for the shielded bearing as it's a modified
original sleeve gear bearing, although there is another on long term
trial in a road going Velo. Unfortunately they are likely to be pricey,
around £85 last quote. But I have recently been given the names of
two companies who may also be able to make such a bearing at a more
reasonable price. Cost likely to be dictated by demand.
I may also show them a chain wheel bearing and get it costed.
The garter seal mod is not too difficult to achieve, but I think is
dependant on certain factors:- the "shoulder/boss" on the inside of
the front sprocket/pulley where it abuts the main bearing inner race needs
to be sufficiently wide for the seal to run on it, mine is approx
200thou and poses no problem. I think that depth was achieved by machining
the inner sprocket face to clear the reinforced "Walker" crankcase.
The shoulder needs machining to be perfectly concentric and smooth so it
doesn't tear the seal lip.
I then measured the thickness of the alloy where the crank sticks
through the case. My crankcase was about 9mm thick, and as it isn't
load bearing where the seal fits could stand to be reduced to accept the
seal. I then bought a seal which was 4mm x 35mm (diameter of the
sprocket shoulder) x 42mm. The seal is a NAK VG - 4 x 35 x 42. The drive
side crankcase was then machined from the outer edge to a depth of
4mm to accept the seal, which can then be replaced without having to
split the cases. This mod should also be possible on cases
which have been "top hatted."
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In answer to Johann Patek's question about replacing the filter
plug, I believe Veloce used a standard gearbox filler plug instead of the
filter plug in later engines, whether for cheapness or any particular reason
I'm afraid I don't know.
I think the answer to an oil tight engine is sufficient/effective
breathers in the crankcases. From the various engines I've seen it
doesn't have to be fitted under the mag, better in an accessible place like
the top of the crankcase over the "map of Africa" But it does need
the internal drilling through the crankcase between the flywheels and timing
gears as on Thruxtons and later Venoms.
I have also blocked off the hole in the crankshaft and the fit of
the sprocket on the main shaft doesn't seem to matter as the engine is
no longer excessively pressurised, at least not below the piston crown.!
#246 Big-bore race bikes are not a good example of my o-ring proposal, they can
change chains and sprockets every race if needed. They use the 520 size to
reduce drag. Street riders need longevity, or they change for the "pose"
factor. A 33% reduction in bearing surface between chain and sprockets seems
like an awful lot. Chains are relatively cheap and available to me, rear
drum/sprockets are not. Plus I am basically lazy and prefer riding to
wrenching any day.
Guess I'll have to find out for myself - but I think I'll thin the gearbox
sprocket from the backside only.
Also, one should use 428H instead of plain 428, it's stronger, lasts longer,
and fits fine in the primary or on MAC final drives. The H means reinforced
(thicker) side plates.
lengths to suit Japanese bikes. I do this and get two primary chains,
it works out cheaper. The joining link has to be 428H as a 428 will
not fit due to the H chain been slightly thicker.
#239 Has anyone tried to use a 525 O-ring chain on the final drive of a S/A Velo?
It is only about .020" wider overall than a standard 530, and the 18% reduction
in roller width should be more than offset by the modern chain's resistance to
stretch. I'm getting 20 - 30,000 miles from the O-ring chains on my more
modern bikes. The ones on the Venom don't last but 6 - 8,000, and the
sprockets wear accordingly.
This is not a good idea for a racer, as the o-ring chains suck up a bit more
power, but for a tourer it seems more reasonable.
#240 Decided to get a new final chain for my '56 MAC, getting ready for the Spring Opener. Is 428
size the proper size to use on this sweet old thing? Have heard a lot being discussed on chains, and
overload has set in
#241 You will have to skim the sprockets down to 5/16" width to use 525 chain, otherwise there
should be no problem. Most modern racers use 520 chain regardless of capacity, I've been looking
after a 160BHP Yamaha R7 now in its 4th season's racing which runs 520 'O' ring chain and never
had one break yet, touch wood! The chain size is still imperial, given in eighths of an inch, hence 530
is equivalent to 5/8" x 3/8" i.e. the 5xx is for 5/8" and the x30 denotes 3/8". 525 is therefore 5/8" x
2.5/8" (or 5/16") and 520 is 5/8" x 2/8" (or 1/4"). There are exceptions such as 532 and 632 chains
available which were fitted as OE to such machines as the Kawasaki ZX10 and Suzuki Hayabusa, but
the xx2 here refers to roller diameter which is larger than the standard designation for these chains
and will not fit normal sprockets. The main thing to watch on a Velo is clearance behind the chain
which is tight especially to the primary chaincase and will not permit use of an 'O' ring 530 chain due
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to the wider overall width of the chain. I would advise use of a 520 'O' ring chain and skimming 1/8" off
the back side of both gearbox and rear sprockets if you go down this route, you should have no
problems with stretch if the correct adjustment is applied
#242 See my posted reply re 'O' ring chains for info on chain sizing. 428 is one of the strange ones
which doesn't fall quite right in the general rule, but is equivalent to 1/2" x 5/16". I've been using a DID
primary chain on my Venom which is sold as an endless primary chain for speedway bikes and is
exactly right for the Velo
#249 Re chains. On all my British bikes I have owned the past few years,
Velo's and Goldies I have always used on the primary drive DID 428H.
The H denotes heavy duty. 428 is equivilant to Renolds part no
110046 and 530 is equivilent to 110056. I tried using a heavy duty
530 on my Thruxton and found it very lightly touched the outer
primary chain. If you go to a bike shop you can buy 428H in long
lengths to suit Japanese bikes. I do this and get two primary chains,
it works out cheaper. The joining link has to be 428H as a 428 will
not fit due to the H chain been slightly thicker.
#251 My reference to race bikes was intended to demonstrate that the
smaller width of chain was not likely to reduce the strength or
ability to transmit power, and yes, I agree that race bikes can
change chains every race if budget or sponsorship permits. On the
other hand, underfunded teams such as the one I support have to make
things last as long as possible and we would expect to use no more
than a couple of chains in a season of short circuit events, although
I would always fit a new chain before a TT race (different
riders/team/bikes/environment). Gearing is changed for different
circuits, but mostly only the rear sprocket and then we generally use
a range of only three or four teeth for all the circuits in the UK.
The front sprocket is the usual (very) hard steel type, but the rear
is Dural, and we are still using the same set of sprockets we started
with in '99. The machine has done 3 full seasons of British
Superbikes and is currently leading the MRO National Powerbike
championship so is fairly hard worked.
We use Regina 520 ORS, and I'm very careful about adjustment - make
it too tight and neither your chains nor your sprockets will last
long. A bit of extra slack might mean it slaps on the swing-arm
occasionally but shouldn't do any other harm. If it's too tight it
not only affects chain wear but also increases stress on gearbox
bearings and upsets suspension function.
Given the amount of oil that finds its way on to the chain from leaky
primary chain cases on Velos I have my doubts as to whether there
would be any gains in running 'O' ring. The additional drag is
unimportant when you have 160BHP but is a significant performance
loss when you only have 40 horses. 'O' rings are great on modern
machines which don't leak oil and the chain would get little
lubrication otherwise, but I find the standard Regina "Professional"
grade 530 RS non 'O' ring chain to work well and have seen little
deterioration in 3000 miles so far on my Venom. I would also add that
changing the chain before wear reaches a point that the sprockets
begin to suffer will extend the life of these expensive items quite
You're right about the 428H, Regina's stuff has 2.0mm thick side
plates as opposed to 1.8mm on their standard chain. As far as joining
links are concerned you should ONLY use links made by your chain's
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manufacturer for that specific chain, there are so many differences
between chains that only the right thing will do!
Pete C.
#253 I agree with Pete C's comments about chains, I use a 520 on sprockets
thinned down on the inside and even with an alloy rear sprocket (the hub's
machined to take Vincent sprockets), they don't need adjusting even during
practice and racing at the Manx Grand Prix.
But where does he get 40 horses out of a road going Velo? Surely he doesn't
believe the figures in the red book, next he'll be quoting 100 mph for a
standard Venom!
Anyone want to peck at the corn I've scattered?
#252 I run a 530 O-ring. I moved the countershaft sprocket out about .050 so it clears the primary
cover. Obviously this mis-aligns it to the rear sprocket but it has not been a problem (put a straight
edge across your sprockets sometime, I bet you'll be surprised how far out they are).
I make my own front sprockets out of worn out Velo sprockets by turning off the teeth and welding on
a new outside from any donor sprocket, this gives the .050 offset. I tried shimming out the sprockets
once but it doesn't help the already fragile drive dogs.
Regarding horsepower loss, I got answers ranging from nil to 10 hp. Regina chain told me there is
some power loss when the chain is cold but when it heats up it's insignificant. Somebody once did a
dyno test, sure wish I could find it. Many small displacement dirt bikes use them.
#255 To the racers: Racing experience, while impressive, has nothing to do with the
question. Long-term durability is the issue, not strength. If I have to throw
a new chain at it every few thousand miles, what has been gained? Been there,
done that.
If you believe the chain manufacturer's literature, a properly lubricated
o-ring chain has no more drag than a standard one. Even 400cc commuter bikes
come with them. The o-rings serve to keep grit and dirt out as well as keeping
lubricant in. When someone reports 20,000 - 30,000 miles on a standard 530
drive chain, I'll buy one like it!
#284 Interesting; In getting the '56 MAC ready for the Spring Opener, I replaced the felt seal that is
positioned over the clutch inside the outer primary case half. Making sure the seal was as even and
as far down in its positioning ring as it would go, I had applied Seal-All adhesive to its positioning ring.
After the adhesive had dried, I soaked the seal in oil over night, but I noticed the seal was not
softened up much, and was pretty firm to begin with. I put all back together, cursing the rubber
seal/metal retaining ring set-up, but finally got it right. Upon operating the clutch lever after this, I saw
that the primary case "bulged" noticeably when the clutch was disengaged, lever pulled all the way in.
Obviously the felt seal was interacting with the clutch, reducing free movement. I decided to carefully
run the bike a bit just to see, and except for there being almost immediate take-up of the clutch in low
gear from a standstill, shifting up and down while running seemed normal, no graunching or hard
changes. So, can anyone tell me if this is normal when initially running a new felt seal, and will some
running in reduce contact or? Thanks
#285 felt seal case-bulging is normal with a new one, at least they've always
done it on mine for the first few months. I've also opened my primary case
at times to find a lot of wool fibers in there. Maybe it quiets the chain!
#286 The felt seal thing; when heated up from hard riding, the clutch would drag when I went from
neutral to low gear, once to the poinmt of stalling. i now am wondering if this is a direct effect of the
seal contacting the clutch combined with some swollen friction plate material, or if the clutch alone
would create this situation. I adjusted the clutch as close to perfect as I could, which is pretty good, so
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it probably isn't a matter of adjustment being off. But if it is like a number of other older bikes I've had,
mostly dry clutch, the plates will swell after hard usage
#793 I have a copy of the BMS Velocette Singles Service Series book which
covers the Venom.
With the inner primary chaincase removed they refer to the bolt head
at the top/front of the engine plates. It says if you want a leaky
chaincase (is there a choice) fit a standard bolt at this location.
This one must have a thin shallow head to provide essential clearance.
If this is true does anyone know where to get one or do I just need
to grind a bit off mine!
#798 If it were me I'd just grind it off (but then again I'm not a purist).
got various electrical "bits" off mine at the moment, so have a good view
the bolt. Its head is about 7/32" thick giving about 1/16" clearance to the
inner chaincase.
#810 Had a quick look at the book. It shows the offending bolt
but if you look closer it is being used / shown with the optional
additional stiffening plate so I suppose that if you use one of those
you need to thin the bolt head down.
#1041 Opening the primary case, I saw the
following problem I never experienced : The primary chain has seized links,
some rollers are broken. The chainwheel is out of alignement, outside 2.5
or 3
mm. There is no sensible end play on the sleeve gear.
I'm puzzled as there is no provision to shim neither the drive pinion nor
clutch or the sleeve gear. Where could this trouble could come from, and
how to
cure it ?
#1045 if everything in your clutch was fitted the right way, my suggestion
that the big threaded ring that secures the main bearing loose and the
whole clutch moved away from the gearbox because of the force you put on
it when operating the cluitch. If the bearing sits relatively tight in
the housing, you won't feel any play.
Anyway, if this is the case you should have encountered some clutch
drag. Maybe you adjusted it and some time later it occured again and so
#1051 regaurding
primary chain alignement, they are usually out of line by about 4-5mm
my freind herman jassing from holland has encountered this problem
and i have fallen foul of it as well. the standard primary chain is a
bit weak if you tend to give the bike a bit of stick. you can fully
streach a chain in 1500-2000 miles if you ride a bit hard. i was told
to fit a 428H DID primary chain which has thicker side plates and is
a heavy duty chain. its a tight fit to the primary case but they are
ok. i fitted one and ran the bike. i had to take the outer chaincase
off and to my horror the chainwheel was eaten away on one side very
badly where the chain was trying to align its self and pulling into
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the chain wheel because the sprockets were out of alignment. it hadnt
done it with a standard chain but the heavy duty chain showed up the
problem. the chainwheel is a fixed item so any adding shims has to be
done at the engine sprocket end. if the engine sprocket is too far
out, you can allways let it down by use-ing grinding paste and a
mirror. rember that a mirror is flat because it is ground and a pane
of glass is not. it seems that all the bikes that were made were not
too well aligned on the primary side. herman has checked alot of
velocettes and they all needed aligning on the primary side. i hope
someone can use this information. p.s. remember that if you do
decide to fit a heavy duty primary chain allways rivet up the link as
split links are a definate no no.
#1053 i mentioned about primary chain alignment and i said
that you either had to shim or let down the front engine sprocket. i
was lying in bed when it dawned on me that i should have said shim or
let down the inner cush drive, as it is that that will determine the
alignment and not the sprocket. my mistake.
#1057 I have taken the bearing ring nut out, it was ok, and the bearing is
snug fit
in the case, so any end play would have been noticed. Thanks for the idea,
Billy, do you mean that's normal to have 3 mm or so out of alignement, and
not why my "normal" chain has been destroyed ? The outside of the
teeth is worn too (the chain wheel is outside alignement).
So the only two other possibilities I consider are lack of oil (there were
few in the case), or too tight a chain. It was ok when I opened the
recently, but I remember last year I found it over-tightened once.
Just in order to check the sleeve gear bearing, is there a way to take it
without opening the gearbox ?
#1060 I have done quite a bit of primary chain (well belt in my case)
work. One thing I have noticed is that if checking with a straightedge
across the chain wheel the state of the trans in the mounting plates has a
significant effect on alignment measurements. This applies to rear chain as
well. The effect riding the bike has on the trans (notice how when you
adjust the primary chain, making sure to leave the jack screw pushing the
trans forward, then go for a ride the primary chain still tightens up as
trans gets pulled back on the drive side only) will change alignment. So
might try moving the trans in the plates and see if there is any change.
Also main bearing shimming will of course change alignment by a small
as will clutch plate thickness.
#1062 It is also possible that the clutch chainwheel bearing is worn, loose
missing (yes, I've seen it missing!). Also, of course, the sleeve gear nut
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being fully tightened would cause misalignment.
#1063 have you checked the mainshaft nut under
the cap on the gearbox cover? That could allow the
clutch to slide over to the left, wearing the outside
of the clutchwheel's teeth.
#1064 The final drive sprocket is mounted on the mainshaft, not the clutch.
#1067 When you checked your
primary chain did you check in five or six different places on the chain.
Every primary chain I have checked has variable tension depending on the
concentricity of the chain wheel. If your unlucky it can vary between tight
to flapping about. It's also interesting to check (with a gloved hand) when
everything is hot, I am surprised how tight it gets on expansion.
#1068 when you stripped the clutch to check on the sleeve gear
bearing was the chainwheel still tight and central on the large
I think Paul Zell has the right idea when he refers to the clutch
plates and inserts wearing and misalignment taking place. Have you
measured the inserts and the steel plates and compared them with the
thickness of new items? I have seen Velo clutches where it is
possible to rock the chainwheel even when the clutch has been
adjusted perfectly, due to worn inserts. A combination of the above
and your own observations of little oil and tight chain could have
caused overheating leading to seized and broken rollers, culminating
in the wear you noticed on the chainwheel. As Geoff states the
mainshaft nut in the box shouldn't affect the clutch, which should
still work and rotate even if the mainshaft is out of the gearbox,
but don't try it too often as the pressure exerted is taken by the
unsupported clutch and bearing and may distort or crack the alloy of
the gearbox shell. you stated in your second reply that the bearing
spacer was the original and the gearbox bearing was still tight so I
can't see what else could cause such misalignment other than the
#1069 I always check the chain tension in different places. For years, I
always had it on the slack side. But last time, I remember I tightened it
more than usual, to the specified value (red book) 1/2 or 1" free play
thinking it would get some more play when hot.
This, added to dry case, could explain the chain havoc.
But this doesn't explain chainwheel misalignement. I checked all the clutch
parts :
Chainwheel was true on the backplate, as well as on the sleeve gear.
Thickness of all plates is right, a bit less than new parts, a bit more
used ones. Some plates are not perfectly flat, but as far as the clutch
worked properly and didn't drag, I do not think this could cause a real
thickness excess of the assembly. Anyway, even without any friction and
plain plate, i.e. assembled with backplate and chainwheel alone, the later
is still outside about 2 mm.
The alignement was checked with a ruler on the outer face of the engine
sprocket (in different positions of the engine, and sprocket). The edge
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point at the outer face
tooth instead. I reckon
the box in the mounting
But I can be wrong, and
of the wheel teeth. It does at the middle of the
this measure must not be affected by the position
plates, as far as the shell is tight between them.
I'll try Paul's suggestion.
Misalignement could be due to wrong spacer length (Dai, do you know the
right length ?). Maybe it has been like this for the last 35 years (never
checked it before), and the oil + tension revealed the prob. This would
such a misalignement is acceptable.
#1070 The primary chain normally tightens when it get hot.
#1071 maybe your problem is due to warped gearbox mounting plates. During
several decades of hard work this might happen. At least my plates were
warped when I stripped the bike although it was fitted with the double
plates at the drive side.
#1072 Both my spare parts list for MAC (spring frame model) list
B35/3 sleeve gear distance piece for the MAC. not B35/2 ? could this
be the problem.endcha
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Racing & High Performance
The easiest way to get your Viper to go faster, is to fit a Venom barrel
and head. Better yet, a Thruxton barrel and head! I have a Viper clubman,
and it won't do over about 90, with a fairly fresh motor. But, I remember at
Montlhery several Vipers, and in discussion with their owners, they all
claimed to get over 100mph out of them, with no great trickery. Any thoughts
on this, fellows?
P d'O
#54 Try shedding some pounds. This is easier to do to the bike than the rider. A 50 pound reduction
in stock bike weight should be close to trying to gain 5 hp on a Viper. I have a Venom based racer
that is down to 240 lbs with fuel and oil (non-stock frame). It makes a big difference
A box of clean spark plugs and a selection of sprockets will do wonders. Spend the time dialing in
your carb and ignition. Make lots of high-speed runs and immediately take those plug readings. A
crisp running engine can add an easy 5 mph to the top end
#35 The easiest way to get your Viper to go faster, is to fit a Venom barrel
and head. Better yet, a Thruxton barrel and head! I have a Viper clubman,
and it won't do over about 90, with a fairly fresh motor. But, I remember at
Montlhery several Vipers, and in discussion with their owners, they all
claimed to get over 100mph out of them, with no great trickery.
#36 I am taking up sprinting using a 1937 MSS running on methanol with an 1 3/16 inch 10TT9,
running on a standard M18/2 with standard followers. The clutch is to Thruxton spec. In my first year
my key objective is to be able to slow the beast down, as currently it has a rigid MAC 6 inch hub
(frame and forks are MSS/KSS). I seem to have been spending the last month converting a cast
MAC/MSS 7 inch front hub to fit the webs. Turned up lots of 5/8 inch to ½ inch spacers (in titanium),
and converting a 5/8 inch diameter spindle to having ½ inch BS Cycle ends. Titanium is a funny
metal; do you know you can get it to ignite when you turn it?
I have been researching the subject of speed. First thing is to speak to all the fast Velo boys at the
meetings; they are only too pleased to be of help. Secondly there have been some excellent articles
on tuning Velos in Fishtail and Fishtail West by Nick Vann, Dennis Quinlan, Bill Melville, Marin
Violette, Robert Gussman,peter Witman and Laurie Nunn. These appeared in a reprint of the
technical articles in Fishtail, by our American cousins. If you struggle in getting a copy of these articles
e-mail me direct(Dai Gibbison)
#58 questions
Valve to Piston clearance - what is the consensus then ? I've been
quoted anything from 50 to 150 thou.
Compression Ratio - is 10:1 enough (or too much ?)(I dont want to run
meths, cos I want to ride crmc too)
I'm just replacing an iron barrel
with an alloy one to lose 7lbs, and replacing the steel tank with an
alloy one to lose another 7 lbs, and the frame is already delugged
#59 While you are busy tossing the weight off your frame, think about getting some serious weight off
your valve train. That will help you raise the rev limit.
Velos breathe fairly well with the 17/8 cam. Problem was they tangle valves just over 6200 rpm
(Venom). Actually they seem to be pulling hard until then which indicates that power is still being
made. Lightening the valve train will allow the revs to increase. There is a problem with this though,
as the revs increase the stresses on the crankcases built substantially. As such, at the same time you
lighten the valve train think about using parallel roller main bearings or machine a steel top hat
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reinforcement piece for the drive side main bearing if you stay with the taper rollers. The drive side
case is definitely a weak point.
I run a 9.75 to 1 compression ratio, Sommerton polydyne cam, and my rev limit is 7,500 rpm (self
imposed). I have run it out to over 8,000 rpm (undergeared and I wasn’t going to let that Manx get
past me on the long straight) and the bike is still pulling hard. I wouldn’t try go to this level without
extensive engine work. I have lots of mods, titanium bits and extensively reinforced engine cases (and
even they have cracked).
Many bikes tend to run out of breath as the revs increase. The Mac, for example, with its mild cam
just tends to let you know that there is no gain in wringing the throttle any more, time to shift.
#60 I have sent you instructions and diagrams of how to lighten, rockers, followers and pushrods on a
Velo direct to your e-mail, as if I publish I may be breaching copyright! Cary these out, and purchase a
set of alloy collars and up rated springs from Nick Payton (about £38 ) and you should be on your
way.(Dai Gibbison).
#61 In reply to your E-mail a short message from Holland.
I'm a member of the VOC and the VCN, that's the Velocette Club Nederland.
Racing is with the HMV, Historische Motorsport Vereniging, a bit like the
Racing Section of the VMCC.
What do I race?
Well, I guess some of you know this bike from the past, it's the
ex-Wilkinson 1938 MSS outfit.(John Nienhuis)
Gidday all,
I'm Mike Tesser from Western Australia.
I am a member of the local WA Historic racing Club and have a '38 Mac.
I'm having trouble with second gear, it broke and I am advised by those
that know that this is a common problem and the best way out is to
replace it with a pre-war MSS box, or it will just continue to happen.
Any thoughts? I am having great difficulty in finding a replacement 2nd
gear in Oz.
The Mac has close ratio gearset and close ratio sleeve gear, SW
springs, triumph front wheel, and runs on Methanol. The barrel has had
the cast iron fins removed and replaced with shrunk-fit alloy roundies
for better heat dispersion. I was using Castrol "R" but due to the
difficulty in obtaining it and the high cost, am flushing out the
system and replacing it with a 50w oil, any suggestions on what to use
given that it does not get very cold over here and we do a maximum of
about 6 laps per race, three races a day plus 2 practice sessions.
4 others from our local Velo club are also racing this year having
built up pre-war 350's to come and play! We are trying to encourage
other pre-war machines as this class is just me at present, so I'm
looking forward to solving a few minor niggles before the season
starts. I have passed details to them about this much needed forum and
you should hear from them shortly - some of you may know them, John
Jennings, Paul Barfoot and Kelvin Climo.
I've posted a photo to the forums photo page if you want to have a
Regards to you all,
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#65 I have checked the spares lists of the major suppliers in the UK and no one has this gear
available as new old stock. Probably because they break!
Hello MT,
yes, if the power goes up on your MAC, the second gear will continually
be a source of trouble. I don't know whether it's cheaper to have a batch of
gears made or replace your 'box with one from a K or MSS, as you'll have to
make frame mod's as well. Probably the cheapest way is to source used MAC
clusters and expect a gearbox teardown frequently.
If your average race is only 6 laps and you're running on methanol, I
would think synthetic 20/50w oil should be plenty for your bike; you might
even get away with straight 20 or 30w synthetic, and I know several vintage
racers who use this. NSU used pre-heated 15w in their GP racers, and that
was 1950's oil. I doubt your engine will get hot enough to really thin the
straight 50, so you'll be losing hp to drag. People use straight 50 to keep
film strength in a really hot engine, but I think in your case it's just a
that's my two cents, Pd'O
#72 Hi Mike et al from NZ,
I have a rigid MAC, alloy eng#16798, (did this start life as
an iron one? -I don't know.) Its close to standard tune other than
raised compression and an older cam (M17/4) but will get to 85MPH
under ideal conditions.
The bike is road-legal and quite light (as am I) and I have used
it with '500' top-gearing, giving a sort-of 3speed plus overdrive
effect in an effort to get more useable ratios. Have gone back to
standard for now and its perfect for 'pottering' as is but on the
winding hilly stuff then Im not really happy with it.
Question is- where do you get a close-ratio set for the early
type (rigid) MAC gearbox? There are no alternatives listed in
the spares books I have.
#75 Can anyone help me with this one?
My Mac racer (pre-war) has Iron head and barrel, with fins machined off
and aluminium fins shrunk fit, running methanol.
Should I run a copper head gasket as per later models, or just lap it
in as per earlier ones?
At the moment the exhaust valve is just marking the piston and rather
than reset it, I'm thinking that the extra clearance gained by using
the copper gasket might be a better option.
Any thoughts?
I think the copper gasket is essential in this case unless you want to start
machining things like piston crowns. If fact, you could pretty accurately
measure your piston/valve clearance by varying the head gasket thickness (it
will compress slightly when you torque the head bolts). Especially as it
seems about at Zero at the moment; a good starting point!
Just out of curiousity, what sort of CR are you running with that piston?
Paul d'O
#77 Cam is Long-stroke MSS 17/3, CR is (If I remember correctly) about 9.5 to 10-1.
I'm also having trouble getting it past scrutineering as the G/box leaks through
the housing somewhat more than acceptably, however I think that this is due more
to worn bushes than anything else as I have fitted new bearings and oil-thrower
shims and the problem persists.
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#78Strangely enough while a close ratio gear cluster was never listed for a MAC, it was for a GTP!
(Owning a GTP, I can’t think why).
The alternative that some of the serious racing carry out is to grind Venom gears to suit.
#79 One way is to run the engine at tick over, and slowly screw out the adjuster until you just feel the
cam follower and valve lift lever (on the engine) make contact. Keep your hand on the lever, you will
feel when it makes contact. Back it off two to two and a half turns and tighten the lock nut. That should
give you 80 to 100 thou clearance. Check that the valve lifter works OK
#161 I raced on short circuits from 1990-95 with an alloy chainguard over
the chain using only chain lube, the clutch release bearing having
been assembled with grease and I didn't have any problems only
renewing the grease occasionally.
In 1997 I started racing in the Isle of Man and reckon I do about 700
miles during practice and race week. I use a belt drive that John
Watson and I developed, which runs dry. I lightly oil the chainwheel
bearing, but just used grease on the release bearing and have not
suffered any problems.
Try a belt drive, it's so simple and John even makes one that can run
within the primary chaincase with or without oil. I also used a
shielded sleeve gear bearing to keep the oil inside the gearbox and
the front pulley on the crank has a "garter" seal to keep the oil in
the engine
#170 I'm in the process of adding crankcase and timing case breathers to
my race viper and venom.
The viper had a small bore breather (1/8 in) on the timing case and
the rocker inspection cover which were obviously far too small to do
anything useful. I've now added a 3/8in hole from the timing case
into the crankcase and a 3/8in bore breather fitting under the mag. I
think these should be enough to stop the piston pumping oil out the
main bearing on a 350.
The venom only had a 1/4in 8in bore breather fitting under the mag,
which I judge as woefully inadequate. This is being uprated to 3/8in
bore too, and i will put a 1/2in breather hole from timing case to
crankcase. These are essential mods for race bikes - or road bikes
used in anger ! If you dont screw the throttle, you wont pump much
out of the main bearing !
The side benefit that noone seems to discuss is that these breathers
shoul also allow the timing case oil drain work, as the piston will
not be pumping oil back up it all the time !
Tony Ainley has a specially made garter seal on his main cos he races
hard !
BTW - there is another belt manufacturer - Ray Thurston's son - who
fits a seal as standard on his kit..
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#238 I am sprinting an iron engined MSS that runs on methanol. What spark
plugs do you use, or would recogmend in iron MSS/MAC?.
#244 I am a velo-novice, probably the youngest member and building
the MOV racer for 2 years. A lack of finance makes my Velo sitting
on the table for 2 years now!
I am becoming a table velo-tuner till I found here to ask
questions to you like experts.
Topic is balancing. Have ever someone balanced the cam wheel
(M series). I think that it have to be balanced with cam in-situ?
I have heard high REV makes a drive side crankcase to crack.
#283 Over the last ten years or so I have been planning to build a MAC sprinter. During that time I
have been researching what I need to do to tune the engine by reading about and speaking to
everyone that races iron Velos. In the end I opted for a 1937 MSS, which is very similar to a MOV.
Some of what I have described, I have carried out – some I will carry in the near future.
Crankcases. The MOV/MAC crankcase is as thick and strong as a Venom, it also has less
cylinder overhang. David Holmes and Nigel Lines who have produced the fastest iron
pushrod Velos have not reinforced the crankcases, so I doubt if you will need to. One of our
fellow club members has converted his main bearings to roller mains, but I am not sure what
best solution is in this area. My MSS has been converted to post war specification that is
taper rollers similar to a Venom. Polish both the inside of the crankcase and the crank to
reduce drag. Also polish the con rod to reduce the likelihood of the rod fracturing. I am not
sure what the balance factor is best so I would leave it as it is.
Cams – The ideal cam for a MOV is a M17/6 similar timing to a Venom but slightly less lift.
Unfortunately they are very difficult to find. Use a M17/8, but you will need to remove about
3mm. from the valve spring cup and the bottom of the rocker box where the rocker touches
when on full lift. Finally if you can’t get hold of any of the above, you can use an iron MSS
cam M17/2.
Valve Gear. Lighten the rockers, cam followers and pushrods as shown in the
attachments. There is also an oiling mod to supply additional oil to the guides, but it is difficult
to describe in print.
Carb – for a MAC a 1 3/32 inch TT carb is the most appropriate and as big as you should
go. However a 1 1/16 inch Amal 276 will do a similar job. Increase the induction tract length
by fitting a one inch spacer between the carb and head. You can use a larger inlet valve up to
1.5 inch. Ideally use a Nimonic 80 exhaust valve from a Viper and turn it down to fit. The
exhaust valve needs to be a loose fit in the guide to avoid seizure. Ideally you should remake
the guides out of aluminium bronze.
Valve springs. Use light alloy collars and springs available from Nick Peyton. Approx cost
GBP 38. You could also consider fitting rocker return springs available from R. F Seymour,
although the jury is out on the benefits of this.
Pistons – methanol pistons although rare do exist. However the most common solution is a
high compression Triumph piston. It will need some fettling to make it fit and to obtain the
correct compression ratio.
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Oil system. Replace the single worm oil pump drive with a double drive worm from a 86mm
Velo. While you are at it, fit a 86mm cam steady plate with the cam oiling jet. This will involve
silver soldering a boss onto the existing timing cover feed pipe and drilling into the pipe, not
the easiest of jobs. If originality isn’t important use a Venom / Viper timing cover and save
yourself all the extra work. If you have a crankcase with the rear cylinder oiling jet you can
blank this off by using an ordinary bolt, rather than the oil feed bolt. Then drill two small holes
the same size as those found in the cam oiling jet in the feed to the back to the cylinder – this
is tricky to get them at exactly the correct angle to spray oil onto the cams. Finally silver
solder two one eighth inch bore pipes near to the bottom of each of the valve spring cups to
help drain the oil away. Use of flexible tube to connect this to a Venom type pushrod tube.
Finally buy a copy of Phil Irving’s book “Tuning for Speed”, it’s packed with practical and useful
information. Perhaps some of the MAC racers in the group can comment or add to my note
May be vibrations or force makes to flax the crank shaft?
What I think is, primarily chain sprocket have to be run as close
as crank centre to reduce effective distance of shaft. This mean
sprocket as close as crankcase?
The end of shaft there is a shock absorber. I think they have to go
as they are hanging a lot! This mean have to use rear hub like
Triumph (with absorber inside) or convert to the primarily belt
#257 1961 Venom with fairing and 3.9:1 top gear = 110-112 mph
Standard Venom top gear ratio 4.9:1 = 96 mph.
#259 In 1952 a methanol-burning MAC set an AMA record of 111.80 mph at Muroc Dry
Lake (now Edwards AFB). The surface was loose silt, giving very little
traction. Not bad for 350cc, eh?
Even more amazing (if even less believable) is the performance described on the
advertisement I have posted in the photo section (under Tom & Zuma). Was the
air thinner back then? Horses bigger?
#560 I got a 58 Venom since two years now and try to get it to its 100 MPH told
By now, the Lucas Racing magneto has been overhauled and the carburettor is a
new Amal Monobloc (checked and re-checked by my workshop), fitted with a 330
main jet. Test after test, the engine is very smooth, but the power "flattens"
when reaching 75/80 MPH with only 3/4 throttle with some impressive vibration.
Looking for any possible reason, I would like to know if this 100 MPH
performance can be reach with the standard 18 teeth sprocket, or if I need to
fit a 19 or 20 teeth sprocket in order to be able (may be) to get the bike to
160 km/h ?
Regarding the vibration, may be the wheel chain tension is too high, and I will
correct that as soon as I got time.
Another question is that it seems that the engine oil is "jetisonned" through
the oil breather tube. I got a recovery bottle (half a litter), fitted with its
own breather tube facing the road to limit the spillage. What is intersting is
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that the bottle is full after 300 or 400 km, but when oil drops comes out of
the forward outlet tube, the oil consumption is then ridiculous.
I had in the past a Ducati Darmah. In the oil breather line, there was a
restrictor dedicated to prevent the oil breather to act as a jet pump (or a
jetison as we call in my job).
Does the oil breather adaptor mentioned in the Velocette Parts List contain a
restrictor or shall I fabricate one in order to be sure that only oil "smoke"
only goes through the breather line ?
The fact that oil consumption comes back to normal figures when the bottle is
full tends me to think I shall.
#566 You will need minimum 19 tooth sprocket, or an enormous rear tyre with an 18
tooth sprocket to pull the ton on your Venom, assuming 6200 rpm rev limit.
For an Avon 100/90x19" rear tyre gearing charts show these speeds per 1000 rpm
and maximum speds in top gear for the commonly used gearbox sprockets. All
speeds quoted are mph:
18 T 15.389
At 6200 rpm
19 T 16.244
At 6200 rpm
20 T 17.099
At 6200 rpm
21 T 17.954
At 6200 rpm
##567 Firstly welcome to the group. Earlier posts discussed top speed of a
standard Venom and in my opinion a well set up Venom with the rider sitting
upright will do about 85 mph + - 5 mph. The 100 mph in past road tests, were
when riders were flat on the tank. Why? Due to the petrol now available,
most Venoms have to run with compression ratios of 8;1 rather than the 8.75:
1, which reduces the power by approximately 2 BHP. Amals tell me that a TT
carb only flows 3% better than a Monobloc so it’s not that. Finally I think
as riders we are all presenting greater wind and frictional resistance as a
result of maturing!
How can you make it go faster? Apart from setting the engine und the rest of
the bike up well, short of fitting a Thruxton head, probably you could get
your Venom head gas flowed. Has anyone noticed that some Venom heads are
stamped G or OK on the cylinder face, anyone know what this means? You could
also fit a spacer between the carb and head to get the induction pipe length
to resonate at somewhere between 5-6000 RPM (if you have room between engine
and oil tank). Lightening the valve gear will only really allow you to rev
quicker and safer. The M17/8 is the best readily available cam around.
Even at 85 mph a Venom does not normally vibrate to any noticeable degree.
Check the following
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Head steady fitted and tightened
Engine bolts tight and holes not worn.
Check your petrol and oil tanks are tight (I spent days worrying about
excessive vibration, only to find I had not tightened the petrol and oil
tank bolt)
Check ignition and cam timing.
Check the carb is set up OK
#571 Don't forget the most important part needed for a ton-up Velo, as used on the
24 hour record bike - a good racing fairing! Worth at least 10 mph, given
proper gearing.
#572 regaurding vfr 232 a 1960 venom
clubman which was a very fast bike. it was fitted with a 12r box. i
was reading one of the posts regaurding max rpm <6,200> and top speed
with a 19 tooth sprocket, which was about 100 mph. i know for a fact
that vfr 232 was cable of a bit more than that. it used to show 105
on the straight with me lying prone. the question i have is, was
there three top gears. one for mss one for venom and one for tt
close gears. 26 teeth seems to ring a bell. if a bike was fitted with
a higher top gear,it surely must give it more top end. my bike was
allways good for 90 in third. i still have the bike, allthough it
hasn't run for some time, but if someone wanted a go on it to prove
its output, i wouldnt be against it. did a tt close box have a
higher top gear than a standard 12 box ?
#573 Top gear ratio is all in the sprockets, not the internal ratios of the gearbox,
as I've never heard of an internal top gear ratio other than 1:1 in a Velo.
The options on sleeve gear and (I think) first gear are what differentiates the
suffix R from the standard series 12 box.
A close ratio sleeve gear in any box will leave top gear at the ratio
determined by the final drive sprocket (or custom combinations of any of the
other sprockets for that matter) but it will bring all of the intermediate
gears closer to top - for instance a 17 tooth sleeve gear (in place of the
standard 16 tooth) in my MAC racer left me with 1:1 top but overall drive
ratios of all the other gears were higher by the equivalent of almost two
gearbox sprocket teeth, when compared with the overall ratios available with
the standard sleeve gear.
So if you'd like to run a 19 tooth sprocket for your ton and a bit Venom, but
have first, second and third the same as if you had a 21 tooth sprocket, then
go close ratio sleeve gear, which for series 12 gearboxes means an 18 tooth
sleeve gear as the standard sleeve gear in the series 12's is a 17 toother to
start with. For sidecar use go 16 tooth sleeve gear - it will have the
opposite effect, and was used in the wide ratio series 14 boxes.
And of course whenever you change sleevegear the layshaft pinion needs to be
changed accordingly (from 16/28 to 17/27 to 18/26 and so on).
Read the chapter on gearboxes in Burris - its a good explanation for those
wondering how the hell to calculate these things called gear ratios.
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#575 thanks for the info regaurding sleeve gears, mine has a 18 tooth
fitted, it is a genuine 12r box. these boxes make a world of diffence
for performance on a venom, but are a pig to use in traffic. they are
definatly for the open road. regaurding fitting a thruxton cyl head
to venom, if you dont shorten the barrel by 90 thou it will be as
flat as a pancake. i considered trying to buy the venom cyl head
patterns and having my own head made. thruxton valve angles are at 39
degrees wereas venoms are at 45 degrees. if i had some venom head
blanks i could have the valves at 39 degrees and keep the stock venom
valve sizes. a thruxton inlet valve at 2 inches is a bit on the heavy
side, and a venom inlet valve at 1 inch and three quarters is a
better bet for higher rpms. any feedback on this is welcomed. when
fitting a thruxton barrel to venom head and tightning up the vavle to
piston clearances, these bikes transform into a fast bike. dialing in
the cam is a must for performance as is accurate ignition timing, it
needs to be set at 38 degrees, and on the money. i seem to remember
that taylor gue of stroud in the sixtes made a venom very fast and
that when they were doing a road test of a thruxton in motorcycle
sport in 1966, they also tested his bike to compare it with the
thruxton and found it to be a faster bike. dig out your old copies
and have a look.
#577 Could you tell me how fast the fastest Venom has ever been, because my 1961
Venom Clubman comfortably went off the clock (about 110 - 115 mph)
#578 RE top speeds. A few years ago while managing a bike shop, Triumph
Bonneville owners would often come in telling us their T120 actually
did 120 mph, we use to tell them to write to Triumph and tell them as
they would want to buy the bike to find out why it was so fast. I
think the same applies to some Velocette owners.
While at the Manx this year I had a T shirt printed with the
slogan "The older I was the faster I was". When wearing it people
came up to me laughed and said they were going to get one for
Re sprockets, I have had no trouble in the past purchasing 21 and 22
teeth ones. The 22 teeth one made my Thruxton do 150 mph (more
dreams), me thinks.
##579 question, does anyone on this forum have
a venom with close box, thruxton barrel, ported head, mk1 and a half
concentric <rubber mounted> carb with stack, modifed cam followers,
dialed in cam <m17/8> clearnces tightned up < valve to piston >,
manual comp mag <set at 38 degrees fully advanced>, piston
compression about 11 to 1, <it pinks on pump fuel and needs octane
booster>, clip ons, rear sets, two way forks, 20 spring clutch
carrier, alloy rims, thruxton gas and oil tanks, and tls front
brake, well i have and i stand by what i say that it used to
indicate 105mph with me lying prone, with a cronometric speedo fitted
and also a cronometric rev-counter
#580 My measurements have differed from yours as follows:
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The valve angle difference between my Thruxton head and Venom heads is not 39
and 45 degrees, more like 39 and 40. Have you seen any documentation on
All my Venom heads have 1-13/16 inch intake valve not 1-3/4.
My Thruxton cylinders are only .040 to .060 shorter than Venom, none as much
as .090.
Perhaps changes were made along the way. As for top speeds, I have noticed
the same bike will do 100 one day and barely manage 95 the next on exactly
the same stretch of road. Seems to depend on air temp, density, direction,
how much air my jacket is catching, etc
#582 Can't tell you how fast the fastest road going Venom is, or was, but can tell
you that Down Under the Sid Lawrence piloted racing 500 (originaly based on an
MSS I believe) was electronically clocked at 132.35 mph down conrod straight at
Bathurst in 1966. It remains the fastest pushrod single ever clocked at
Bathurst. It was in no way a road machine, with Featherbed frame, fairing,
squish head, and home made GP carb (engineer extrordinaire Allan Russell made
one when the team couldn't buy one!). For full details ask DQ or JD - they
were both involved in the development of the two "Smith" machines, one of which
in later years was ridden by Lawrence.
As for the capacity for sustained ton up speed of basically stock Venom based
machines don't forget the Montlhery record breaker. It had to be lapping at an
average approaching 105 to allow for the stops (and the gearbox repair).
#587 Concerning speeds; When I first bought VMT 260 it would do 110 no
problem, in a racing crouch, but not 'under the paint', and on level ground
(actually the first time was on the Golden Gate Bridge at 4am); this was
clocked from a calibrated BMW. Over time this decreased until it would no
longer do 'the ton' as the top end slowly wore out. Then I knew it was time
for a rebuild! It was surprisingly consistent on top speed once it was
properly warmed up, like at least 30 miles.
Maybe your Venom will do 105, but the best I've ever managed on one (and
I've owned three) has been about 98mph. The Thruxton would out-pull the
Venom any day from a rolling start.
And concerning the record breaking Venom; this has always given me
confidence! In fact, VMT 260 had logged many many hours at over 90, and as
JJ can confirm, is as docile and reliable as could be asked for.
I think the top speed for a Thruxton at Bonneville is only about 118,
#614 Venom top speeds , I doubt very much if a standard Venom will top
95 and ever did . The Clubmans models however are another thing .I
know we has the slide rule deminstration that at 6200rpm on 19-21
teeth the VM will not do 100mph , but science says the Bumble bee can
not possibly fly either . I think there are a number of factors to
consider . a) we all love a downgrade and following wind . b) no-one
throttles back at precisely 6200rpm . c)If you look at record
breaking and timed runs they are always 2 way and there is ALWAYS a
difference .d) gearing calculations will probaly be inaccurate due to
the tyre fling the dragsters love and rely on so much at high speed .
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I have in front of me a Motorcycle Mechanics from March 1965 with a
road test on a VM Veeline Clubman ( has the Avonaire fairing ). quote
highest attained speed 104mph ( electronic timing ) , highest
indicated speed 112 MPH .
#617 The Sid Lawrence,record of 132.32mph DOWN conrod straight at Bathhurst
as the fastest single pushrod ever
#622 for people who have never seen or
heard of Bathurst, that conrod straight is unlike any where else in
the world. It`s comparison to Bray hill was to emphasise it`s
gradient,and that it is miles longer, The records achieved there are
the lucky one`s that have not put their con rods through their
crankcases hence it`s name conrod straight.
#627 Having ridden a Velo over the TT/Manx course under racing conditions, I
think it fair to say that Bathurst would be faster.
I've see motorsport from Bathurst on TV and I think the greater length
would allow the extra speed.
Tim Johnson on his Venom went through the Grandstand speedtrap at this
years Manx at 110 mph, admittedly he was still accelerating and he had the
joy of plunging down through Bray Hill, but I doubt he would exceed 120.
#700 I am one of the mad group in West Aust who are racing
Macs however I have encountered a problem. When I
rebuilt my MAC I used a SKF NJ 2/22 TN9 roller
bearing on the drive side ( this bearing has the same
I/D same O/D but is 3mm slimmer than standard).
I need another bearing for my spare motor and
I have been told by my local SKF supplier that it is
now deleted from production and they don't have
anything near.
Can any one advise a suitable alternative or locate
a bearing to help.
#789 I am putting together (just starting) a scrambler project but know
very little of original specifications. It's a later bolt on rear subframe model. I know several superficial differences between it and
the road going models but need some finer details i.e. engine and
gear box specs, I suspect a Venom engine but are they standard or
modified? What gearbox, ratio's etc. Any info gratefully accepted.
#942 Warning! Anything potent enough to raise octane significantly in
small amounts will likely be so poisonous and/or carcinogenic that
you wouldn't want it in your garage, much less toolkit or tankbag.
Remember Dave Allcock...
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#943 if all fails should I fit a compression plate to lower the ratio if so
what size, where should i get it from (Its a thruxton standard bore).The
in there now came from Goodmans. Is there a superior piston out there that
handle this problem?
#944I have spoken in the past with a fuel chemist, and he recommended
xylene at NO MORE THAN 10% to gas if octane boost were needed. Toluene I
would imagine is much the same, but I wouldn't add 20% as this might bring
new problems due to altered burn rate and excessive heat.
#945 The Velo tech website (thanks again Dai) has the formula for C.R. vs.
compression plate thickness. Plates normally come in 0.030" and
0.010" thickness, I'm running 0.050" under my Venom's similar barrel
(it came with these plates from the factory). It never pinks now,
even on our watery U/L premimum, as long as the fuel mixture is
adequately rich. Plates are available from the Usual Suspects - oops
I mean Sources, check the List archives. As a Velo rider, you will
soon be on a first name basis with them. And I strongly recommend
that you join the VOC and VOCNA; the VOC's Spares Service is
excellent. See the VOC website for links.
I assume you have an Omega piston, I have had some trouble with them
seizing but never had one fail structurally. There are few
alternatives in any case, unless our Aussie mates have made some
more? Pretty please?
But before I detuned my VMT I'd double check the ignition timing,
make sure you haven't fitted an extended tip sparkplug (such as NGK
BP7ES instead of B7ES) and that the fuel mixture is adequate. There
must be no blocked jets or air leaks.
#959 I might make another suggestion since most of the logical things have
been mentioned, if you want to take advantage of your compression and
use the highest available octane, install a cam with more overlap and
a even little more lift (commonly referred to as "hotter")if you feel
cheeky. This will effectively lower compression by opening the valves
longer during the cycle and give you the power that the compression
is there for and should stop the pinging if everything else is
standard settings. The shim plates are poopy in comparison.
#961 Increasing overlap gives more time for the fresh fuel/air mixture to
cool the combustion chamber. It will also reduce low rpm power and
fuel economy; there is no free lunch here. I have two modern, 4valve per cylinder motorbikes that suffered intake valve damage from
inadequate cam overlap for their higher-than-original compression
ratio. The symptom is that the intake valve clearances close up over
time. Interestingly, the seats are harder than the valves these
days. The cure in one case was to change the cams, in the other a
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reduction in compression ratio is needed - it already has a hot cam.
The easiest way to increase overlap on a Velo is to increase the
radius of the cam followers - oops Veloce already thought of that!
The difference in power characteristics between MAC and Viper
illustrate the difference perfectly.
#962 I meant to mention that this cam change should include a duration and
timing change as well (this goes with high peformance cams as a
matter of course), which will require a regrind. It is definitely
true that changes like this are detrimental to low end performance,
you will get a lumpy idle and less grunt off the line, but in the mid
range and up, it will be sparkling! I like regrinding because you can
get a higher lift without a taller cam profile from centerline (the
backside of the cam is ground down to give the higher lift), thus
avoiding clearance problems.
#1020 I have my race venom in bits just now, so I will measure the
pipe for you.
It is more than thruxton spec, so I think it classifies as 'tuned' !
I run end-cans on the venom and viper for racing that seem to do
enough silencing, and will measure those for you too.
In general terms, if you are going to sprint, you will obviously get
a bit more power if you run an tuned straight pipe, but you always
lose out if you think in absolutes !
The answer is usually a compromise, and reverse-cone megas are
exactly that.
#1030 I have now spent the season experimenting with
a variable exhaust pipe extension and settled on 45 inches along CL. This
seams to resonate with the induction length at about 5500 RPM. I knew I got
it right as for the first time the bike wanted to over rev, the valve hit
the piston and the rest I am sure you can imagine.
#1055Here I am spannering my Venom racer, trying to reduce all the leaky
areas ...
I've fitted a much larger bore to the engine breather - ok.
I've drilled the timing case to crankcase hole - ok.
But - I undid the pokey leaky external (1/8 bore !) pipe and
fittings to see that the fitting in the crankcase shows me the side
of the flywheel ... now this type of mod is a 'good idea' is'nt it ?!
Well, surely if it lets all the oil out straight onto the flywheel
it's going to cause drag ?
#1058 I assume you are talking about a drain mod from the timing chest to
crankcase? - There is no technical article that I am aware of.
If you think it through the oil supply to the timing chest is constant, so
you are going to get the same amount of oil through to the sump, it just
takes a quicker route to get there. The scavenge rate is greater than the
feed, so when running most of the oil is scavenged from the crankcase. The
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cupful or so that you get when you drain the chain case, is the oil that
makes its way from the rest of the engine when the pump has stopped.endrac
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#5 I'd just like you to know of the existence of yet another, even more
specialised egroup concerning Velocettes; the KTT egroup. It was founded
with much the same idea as this Velocette technical forum, to create a space
where owners of KTT's could join heads on ideas, parts, data, opinion, etc.
If you fall into this category, join up, we could use your input!
yours, Paul d'Orleans
moderator, [email protected]
#29 the Velo OC Thruxton Registrar would be glad
for anybody to sent him the numbers of their Thruxton, whether or not the
owner is a VOC member. His name is Ray Thurston
#31 By the way, I am wanting to obtain the Haynes manual for the Velo Singles to add to my growing
library, but no luck.
#43 the compendium of tech articles which dai referred to was put together by
Tom Ross, who can be contacted at; [email protected]#p...
#54 I copied the list you provided through the VOC of all the technical reports from past Fishtails. Is it
possible to get copies of any of these, and if so, how?
#55 The only way you can get copies of these individual articles is through the VOC UK club librarian.
His details are in the back of Fishtail
#50 Yes, the Haynes is out of print. I have an original copy of the Service Manual for the 1953
SwingArm MAC which should probably cover 99% of the 1956 models main service needs. Also
picked up an original copy of the owners manual which is a LOT morein depth then the ones we get
these days. "Warren Troy" <[email protected]
#51 Warren, there are several sources for out of print Velo manuals. As
Bruce mentioned, ebay is a good one and Velo manuals crop surprisingly often.
To skip all the browsing through Harley parts, I usually shorten a search to
'velocette', or 'motorcycle manual'.
There's also, where I've found literally hundreds of
difficult to locate titles on motorcycles. If you log on, it's pretty
self-explanatory, and there's none of the waiting as on ebay, but be careful,
you may get hooked.
Also, there's ARTCO, that's,
#57 I have both the Haynes manual and the Main-Smith one.
I find the alternative pics the most useful parts, as their tech
stuff is mostly the same as in the red book.
# 169 I have just jumped on here.....
I have inherited a Velocette from my late Grandfather. It is a 249cc
2-stroke, dating from 1929, reg no EN 4251 (light two-fifty, or Model
U, maybe looking at the pictures etc on the velocette owners club
website). Owned by my Grandfather since about 1938, and ridden
extensivelt around the Lake District between than and when it was
last ridden (when it was involved in an accident) in around 1953. I
believe that it is essentially complete, although it obviously needs
a full restoration! The bike is currently in the Lakes, waiting for
me to move it to Scotland so I can start the (what will no doubt be
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long and protracted!) restoration!
I believe that the reg number was registered with DVLA in the early
80's when they went computerised, so I am interested in becoming the
registered keeper, but we cannot find any documents amongst my
Grandad's effects. I have got the from from the PO, but it has a
space for chassis number, so anybody got any idea where I might find
this, to save me hours grovelling round with an inspection lamp?
I'd be interested in getting in contact with anybody out there who
has tackled the restoration, or keeps up, a similar machine, so I can
depress myself with the task ahead....
#171 Richard
While I don’t have a model U, I do have a GTP that is similar in a lot of ways - the next generation so
to speak.
The issues I foresee MAY be the following. They are mainly limited to sourcing parts that are beyond
If the steering races are worn, these are impossible to get hold of. Similarly cups and cones for the
wheels are difficult. I also believe it has a three speed box and parts for these are difficult to get hold
of. The engine is simple as with the GTP just phosphor bronze bushes for main bearings.
Frame number should be found on the lug at the junction of the seat tube and top rail on the off side
of the bike. If not look around near the bottom of the down tube again on the off side
#184 Hi! I have a 1960 350 Viper with clip ons Webb racing tank & Webb
racing seat.Brought to NZ in 1970. [2] A 1948 MOV very good order.
[3] A 1954 MAC first of the swingarm model.[4]A 1961 VEMON ex
Stevens Velo agent of London personal bike with lots of his goodies.
Shipped to NZ,then Australia,back to NZ,i am the 4th owner.Plenty of
Velo crankcases[short stroke]& long stroke,brand new air forks
outers,bronze head for a 350 Mac,gear box parts,new big ends &
valves.Brand new front double link brake unit.I can be contacted at
my e-mail address.Cheers Ashley. New Zealand. [email protected]
#200 Just snapped the chain on the Bandit but only about a mile from home.
The chain was lying at the side of the road in its much lubricated state. The
problem was to pickup same without incurring much blackened fingers.
Solution: - Go to the trees at the side of the road and retrieve some of the
plastic bags hanging from their branches.
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#222 I am about to help a friend who has just acquired Venom to complete his
first service. To help, I have put together a service checklist that you may
find of use. Please let me know if there are any errors or omissions.
#302 Finding it hard from archive photos to tell which alloy surfaces should be polished and which left
'rough' on my '68 Clubman 500 rebuild.
Timing chest cover is obvious but what about brake plates and surfaces on other side of hubs?
Gearbox cover on kickstart side? etc.
#304 Regarding which areas to polish on a Velo resto;
timing cover
valve inspection cover
gearbox outer cover
brake plates
hub backs
Some people do a lot more, like crankcases and gearbox cases, and some
Velos came with unpolished timing covers and gearbox covers (the Specials,
with fiberglass engine covers), which sometimes show up on other bikes.
Engine/gearbox cases were very clean as cast, but not polished
#306My '68 VMT came from the factory with fully polished engine and
gearbox cases. It is totally unrestored (some might say neglected)
and the only remaining polished area was found behind the primary
case! The first (and only previous) owner was definitely not the
polishing type, more of a "working machine" sort. OTOH, my Veeline
was completely "as cast". It had f/g covers that hid everything up
to the bottom of the fuel and oil tanks. The difference is very
obvious, the castings are quite rough. I polished the timing cover on
the Veeline myself, not a Simichrome job, needed my buffing wheels
and plenty of compound. Still not sure if it was a good idea.
I have read that the factory left the engine and gearbox unpolished
on Specials and Veelines to save the labor. Plus it cools better.
But most Velos came with polished cases. Not like a mirror, just
bright. I applaud any attempt to resist "overpolishing" your Velo,
too many are overdone.
#307 I have owned both my Venom and MSS since 1973, they too were unrestored. Polished areas
were consistent on each set of castings covering the following
Timing cover
T/S crank case around timing cover periphery, front edge of pump housing, front edge of filter bolt
housing, front right hand side of T/S crank case
D/S crank case barrel flange, front and bottom of face of crankcase
Gearbox cover and sleeve gear cover
Top inch or so of the shell where the serial number is, right the way around to the concave front side
of the shell.
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Front and rear break plate
Front full width hub on the near side
3 hole disc only on the rear FW hub
I was also told by an ex Velo dealer
#308 This email message is a notification to let you know that
a file has been uploaded to the Files area of the velocette
File : / Click Here!
Uploaded by : jossph6ys <[email protected]>
Description : No matter what your credit is like ,there is a card here for
You can access this file at the URL
To learn more about file sharing for your group, please visit
#323 The Red Book is essential. I only use the Haynes manual in conjunction
with the Red Book because of the photographs. The other manual I refer
to frequently is the BMS Service Series book. It has lots of useful tips.
#330 Okay,so I'm green.After all this is my first
attempt;,but what is the Red Book & where is it
#332 Generally, when people on this side of the pond speak of the Red Book
they mean the Service Manual published by the factory. The Burgess book
is another good source of information, but the emphasis is on the older
(pre-'53) machines
#333 I've found that ebay is actually a good source of manuals, even if one
went to an insane price recently. I've bought manuals for just about
everything there, or found connections to people who have them; sometimes it
just takes diligence. If you send an email to a vendor (those are the people
with 300 plus beside their name!) asking them for something specific, you
might get lucky. Currently the price average for a 'red book' or Haynes
manual is about $40us. Often these are advertised in the Fishtail or VMCC
newsletter, or even Old Bike Mart. Seek and ye shall find. Also, for those
literate souls with a computer, may be useful; just type in
'velocette' under the book title, and you may be surprised at what you come
up with.
#334 The “Red Book” refers to the original service manuals issued by Velocette for the MSS, Viper,
Venom and Thruxton models. They differed slightly over the years, the final ones being the best (and
the easiest to obtain) publication number F484/11R dated march 1971.
The “Red Book” Paul refers to written by Burgess covers M, K , GTP and LE is not as comprehensive
as model specific books, but is worth buying if you see one. For earlier Velos service manuals are
brown, buff and pink!
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You can buy photocopy reprints of any of the service manuals from either the Velocette Owners Club
or Bruce Main Smith publications Personally I prefer to buy original
second hand copies, which are often available from the booksellers at auto, jumbles, normally
retailing at GBP 12. When I next go to an auto jumble I will provide details of the sellers.
Finally, I believe that the Red Book is the best and despite having built four Velos I always read the
relevant section in the Red Book before starting work on any job no matter how small.
#335 Thanks for your replies re. 'Red Book'.I've got the
Service Manual - I just didn't understand the
terminology - the cover of my copy is white.
#355 The Model U I have inherited has now arrived at my house, and I have
had a chance to examine it in detail for the first time. AFAIK it
was last used around 1953 when involved in an accident - but some
work has since been done by my Grandad - the tank for one has been
taken off and cleaned.
I am trying to understand the controls it should have (getting ahead
of myself? - I think so - the engine is stuck (piston in bore) - I
have filled the cylinder with diesel, just waiting for it to do its
thing). The bike has been modifed in use (I'll post some photos when
the film is developed), and is fitted with a twist grip - is this
original? What is the small thumb lever on the LH handlebar for should this be connected to the decompressor on the engine (and what
is that for anyway?).
The bike is also fitted with a type FD Maglita - but the lighting
function has been disconnected - a groove has been machined into the
flywheel to take a v-belt, and we found a battery support bolted onto
the frame, so assume that at some some time it has been fitted with a
dynamo. Has anybody got any info on the Maglita?
Thanks in advance.... My plan is to get the bike back up together
for 2004 when it will be 75 years old, so this will no doubt be the
first of many pleas for info!
Amazingly BOTH tyres hold air, and the rear - which looks as if it
was almost new when it was taken off the road - has obviously been
kept in the dark as it still looks serviceable - the bike will
rarely - if ever - be ridden on the road (for one thing I don't have
the necessary full bike licence - yet!)
#358 There was even a super-sports variant, the USS,
> produced in 1929 only, which was good for nearer 60mph.
Mine was registered in July 1929 according to DVLA (fortunately the
appropriate things were done in the early 80's and I was able to get
a new V5 without any trouble). What were the differences for the USS?
> As regards the controls, I have seen them with both lever and
> throttles.
Dismantled the twstgrip last night - it is indeed the internal scroll
type. Not sure it is original as it is fitted with a distinctly
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homemade looking shim on the bar.
> Reversed clutch and brake levers,
? Front brake is set up on the right - is this normal or reversed?
> magneto lever on the left,
Can see no evidence of a cable entry to the Mag, but then most of it
is covered with about 1/4" of oily dirt- which has fortunately kept
the worst of the rust at bay.
> I don't know that all the two-strokes had decompressors (the
> early 20's models didn't), but if yours has one it's for
stopping/slowing the
> machine, not for starting.
Definitely got one above the LH exhaust port, but no cable connected.
> I hope this helps, best of luck, Pd'O
Yep, always keen to learn/understand more - I am a long way off
worrying about getting the controls right though!
#439 There does seem to be a lot of conflicting
technical information for Velocettes.
#447 I have a Le Velocette mk1
I am trying to identify the greyish colour, that they are painted.
Does anyone know the exact colour and where I can get it
#452 According to Roy Bacon's book "Velocette Flat Twins" the colour schema for the
Mk1 from 1949-50 is:
Main frame pressing, top and bottom fork crown, front mudguard, front fork
front fork lower shrouds and saddle bracket in silver grey. Polished alloy leg
shields and wheel rims, chrome plated fork stanchions and headlamp rim, dull
chrome plated exhaust pipes. Black headlamp shell, handlebars, headstock,
radiator surround, rear engine pressing, rear fork footboards, cylinders, sump,
hubs, generator, silencer box, number plates, battery strap, stand, rear brake
pedal and pannier frames. Also saddle top and pillion black and black footboard
#453 Can I use Araldite "Rapid" to plug a leak in a petrol tank?
#455 Many years ago I used Araldite to repair seeping welds
underneath a Gold Star petrol tank that had being
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repaired and welded by a tank repair specialist and
had no problems. I got the weeping area hot with a fan
heater so as the Araldite ran into the weeping area as
well as on top of it. It worked for me.
#457 As Araldite is epoxy, as far as I know, it is supposed to be petrol
#462 Thanks for your reply. I went ahead and used
Araldite Rapid (a large blob, reinforced with a small piece of cloth)
before I'd read your message. Bottom line is... it
worked! That's 3 days with no sign of a recurrence of the leak.
Speaking to a chemist I gather there's apparently no reason why
Araldite should dissolve in gasoline. I guess the only problem may be
lack of adhesion of the resin to the metal surfaces over time. Still this was a cheap temporary repair that lasted a 250 mile ride on a
sunny day and longer. I left a polymerised "blob" of Araldite
immersed in petrol in a jam jar overnight as a control after
effecting the repair and there's no sign of deterioration of the
polymer. So - this was a "cheap fix". Time will tell.…
#468 Some of the MAC / MSS type single width hubs seem to
come in a kind of metallic green'ish colour.
Does anyone know :a ) what the color was ( is now )
b ) was it specific to some models
c ) what models ( was it the Green bikes only ).
#469 Vipers were made in a colour called Willow Green between 1956 and 1960 – not
sure of the equivalent colour today.
#470 I also used araldite to repair a T90 cylinder head same place and
also araldited a TR6 clutch together,we also use it where I work to
repair steering units for the Challenger tank..
#486 Don Mitchell Tel: 0116 277 7669 has some original copies of the red book called
"Service Manual for Viper, Venom, MSS, Clubman, Scrambler Models and Thruxton
supplement" Publication number 484/12R probabaly issued in about 1972. 124
pages. About £12. This is very similar to the photocopied (larger size)
reprint issued by Veloce Spares under part number VSL102 at £7.70.
#490 There is "VELOCETTE MOTOR CYCLES, a practical guide covering models from 1933"
by R. W. Burgess, edited by C. A. Pearson Ltd., my photocopy is from the 3rd
edition from 1956.
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Another "Red Book" in the same format is "The Book of the Velocette (Covers the
LE and Valiiant "twins" and the Single-Cylinder models up to 1958)" written by
Ferrers Leigh, edited by Sir Isaac Pitman & Sons Ltd., mine is the 2nd edition
from 1959.
#553 3. does anybody know the ISBN No. for Ivon Rhodes book Technical
Excellence Exemplified I am told it is out of print now ?
#555 The ISBN is 0-85045-717-3. Yes, it is out of print. It frequently
turns up on a search for "velocette" on eBay.
#595 Please do not laugh at my Velo. Velo is not only metal but rubber
bands and clamps. because since I get as basket of parts, I do
not know where I can get bolts and nuts. I saw stainless ones (
too expensive ) every where but I need is good set of nuts and
bolts for my MOV. Do I have to buy one each from the parts
catalogue or some one selling the set( for engine and gear box)
I am happy enough with steel ones but if they are well sorted (
length of threads ,etc)
#600 I've often sen adverts selling bikes which mention that the
Registration Number is non-transferable. When I got my Velo last
week, included in the paperwork was a form from DVLC saying the
previous owner had been successful in his application to register
the bike under its original number, and adding that the number was
Just out of interest, can anyone explain why some numbers are
transferable and some aren't?
#603 In the early eighties the Driving and Vehicle Licensing Agency computerised
their records. At that time you had to apply with your buff log book to
register your bike - if you did then your numbers transferable. After that
date you had to apply to get your original number and depending on the mood
of the DVLC ,you may or may not have received your original number, however
it won't be transferable. The above explanation is a little over simplified
but basically that's it.
#610 In the early eighties the Driving and Vehicle Licensing Agency computerised
their records. At that time you had to apply with your buff log book to
register your bike - if you did then your numbers transferable. After that
date you had to apply to get your original number and depending on the mood
of the DVLC ,you may or may not have received your original number, however
it won't be transferable. The above explanation is a little over simplified
but basically that's it.
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#616 Can anyone tell me which numbers (engine, gearbox, frame) should match?
My 1951 MAC has matching engine and gearbox numbers but they don't match the
frame number.
#632 I have never known all the numbers to match, as Velocette built engines,
frames etc and put them into the stores for assembly later. The only way to
confirm this is to check them on the original factory records held by Ivan
#633 I can confirm that it is rare for any two numbers to match. The gearbox
number would be stamped with a prefix which I assume Tom is ignoring.
Depending on the model there are generally a different number of digits in
engine, frame and gearbox numbers. Then there are various alphabetic
prefixes and suffixes. I would guesstimate that 50% of machines no longer
sport the original set of numbers.
I keep a selective record of the machine details returned by VOC members,
some 5000 plus machine entries to date. Within the bounds of
confidentiality, I will be happy to interrogate them on request.
#634 This is getting even more puzzling then, because my bike has engine number with
the prefix "MAC" and gearbox with the prefix "9-" both followed by the same
5-digit number. (The frame number is different.)
#655 Velocette MAC 1951
Today I began the process of neutralising the rust in my tank and applying a
sealer. The first stage was to pour in a de-greasing agent and slosh it
around. Then I had to wash out the tank with clean water to remove all trace
of the sudsy stuff.
When I'd finished I noticed that all the water has made the "velocette"
tank-transfers wrinkle and start to lift.
As it was a sudsy water solution which caused the problem, I'm assuming that
they were the slide-on type transfer and I've got a couple of questions if
anyone could advise me on how to go about replacing them when the job's
finished:Any tips on the best way to remove the old transfer remains?
The VOC parts list includes " A132 - Tank Transfer (modern)" Is this the right
one, and if so, is it a slide-on type?
I was thinking of applying the slide-on type transfer and then giving the whole
tank a coat of spray laquer. Does this sound like a good idea?
I'd be grateful for any pointers.
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#657 I have got the same problem the Velocette tank transfer has wrinkled
its been like it since I have the bike so have no idea what caused
it, the rest of the tank is perfect,
The problem is how to remove it without damaging the enamel? I have
two water slide transfer to replace them, I am told if you use a drop
of washing up liquid in the water, it reduces the surface tension so
they can be positioned easily without wrinkling, and gently pad dry
with a tissue then leave for 24 hrs, before trying to use any sort of
fixing spay, I certainly would not try lacquering the whole tank, as
any Paint sprayer, will tell you need to remove all the silicones
from the surface which is very difficult to do, without damaging the
I am not sure of the best way to fix the transfers, onto a polish
surface so they are permanent. Are there any experts out there to
tell us the secret.?
#661 I've got an old Velo manual - unfortunately it's lost its front cover so I
don't know the precise title or year but it has the following section on
"fixing transfers":
"Transfers are printed on duplex paper and the two sheets must be separated
before transferring. Divide them by rubbing a corner of the transfer.
Apply a very thin and even coat of adhesive varnish to the face of the
transfer and keep as close as possible to the lines of the design. Allow the
varnish to set until very tacky and then place in position. Press down evenly
and firmly and drive out all air bubbles by rubbing with a soft cloth rolled
into a ball, commence in the centre of the design and work out to the edges.
Then with a damp - not wet - sponge or washleather press down again taking care
not to move the transfer. When you are absolutely certain that every part of
the transfer is in contact with the surface apply water freely with a wet
sponge. When the support/backing paper is well soaked lift it up starting at a
corner and peel and/or slide off. Press the transfer down again. Sponge with
clean water to remove all traces of material on the surface of the transfer this is very important as unless properly done the transfer will crack on
drying. To remove all traces of adhesive varnish around the edges of the design
use a wet sponge to which has been added a drop of paraffin, quickly wipe off
with a damp washleather. When the transfer is dry - about 24 hours - varnish to
add lustre. It must not be varnished directly it is transferred."
#663 My 1952 red book manual for the MAC. chapter on transfer, is more or
less the same as Professor Lunt, quoted. except it says use the old
fashioned goldsize, instead of varnish. but that was 50 years ago.
The A132 tank transfer (modern) is now the replacement supplied from
Veloc spares ltd, which suggests it will be the modern water slide
type, not the old duplex type transfer, So the water slide type
should be applied as I said in my earlier mailing. It is the way to
spray fixed it after? to stand up to the all that spit & polish that
we lavish on our pride & joys these days, I would make sure it is not
a cellulose base spray.
#666 I cannot say I have fully mastered applying transfers even after rebuilding
a few bikes, but here's my experience.
Varnish transfers - when you get them right they are the best, but they are
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not easy to apply. I have an oil tank with all the letters attached but if
you look closely it looks like "alphabetti spaghetti" . Follow the
instructions posted by George. I have used Polyurethane varnish
successfully, but you must get the tackiness just right. Buy a spare
transfer and try applying one on a can first!
Waterslide are easy to use but they can appear translucent rather than
transparent. There is no need to use washing up liquid as they float off
easily, infact it may cause problems with subsequent lacquer adhesion.
For both types of transfers I always rub the tank down carefully with
something like 1000 to 1500 grade wet and dry to remove any high spots. Rub
two pieces of wet and dry against each other first to make it even finer.
After doing this you can polish back with T cut if you want.
You can lacquer over the transfers, I have used two pack with no problems,
but I suggest you buy a spare transfer to see if there is any reactions
#715 I'm about to buy a 1958 Venom. I want to restore it to what it
looked like (without being obsessive about it). I'd like paint, transfers,
mudguards, seat etc to be right but I'll use stainless fasteners etc.
welcome on how to find out original spec as looking through various
websites I
can find lots of 1958 Venoms which look quite different from each other.
also like advice on which workshop manual(s) are best.
#716 Best thing to do is get all the manuals and info and decide which
picture of a
58 you like best then buy or build or adjust the bike to suit you. Parts
always be added or replaced. I think overall it is good to buy the bike
running and fixed up as there is a lot of problems in a rebuild that are
frustrating. I have done this to a 59 and it turned out to be a great bike,
one i had done by someone else was horrible. With the Velos you get a lot
flexibility as to what the bike "should look like".
#719 I would concur with the what everyone else says regarding rebuilding
Venom. Attached is a link to 1958 road test of a Venom in Clubman trim,
which you may want to use as a starting point.
Even the official Velo catalogue for 1958 was incorrect as that
year the tank had badges rather than transfers.
Contact Mortons Motorcycle Media who can provide you with photocopies of
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road test for that year
#731 you might want to get a good record first of everything that this
motor does or doesnt do 10 miles wouldnt be enough to find that
out.......especially with a bike your not familiar with...I have done a
few,,,,,,,there easy to take apart not so easy to put back properly
Detailed notes on the workings and the dismantling always help including
....also what is the known history that may help too.
#769 Would anyone happen to know the approximate weight of a MAC. (If
anyone has
specific data to hand, mine is a tele/rigid).
#773 according to MOTOR CYCLING, July 26, 1951, weight is 330 lb (dry
weight?) for
the rigid MAC with Velo front fork.
#777 I just weighed ZUMAC, our 1950 iron rigid MAC w/teles. It's complete
and running, but no toolkit and has about a gallon of fuel in the
tank. 150 front, 164 rear, so Walter's number is "wet". Oh, and
there's no pillon seat, you can see this bike in the Pics section.
#807 I've been in Velo's for 20 years, been active in
the Aussie club, but have never seen a Scrambler in Australia. (I
also ride dirt hence my interest in them) Does anyone know if any
were imported down under or were they a US only model?
#822 Hi Dai. sorry for being a bit dim about computers, but I have a
problem in storing your file in my docs/velocette folder? unlike the
excellent compendium articles file in word format which can be
browsed offline at leisure. the Dr sparks scaned files are in jpeg or
gif format so cannot be stored easily offline? they seem to req photo
editor or pro paint to open them and then enlarge to a read them some there any way round this one? rather than having read them on
#836 Done, loaded as a rich text format for your word processor
#825 One of the previous postings suggests Car Plan Vauxhall
Antique Gold as a good match for petrol tank lining colour. It seems to be
unavailable, at least round where I live. Any others suggestions welcome.
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#831 You might want to contact one of the specialist painters such as
who do gold lining on petrol tanks and have the original templates.
They are extremely helpful and answer EMails.
#835 I use 0.25 inch gold tape from car accessory shops, applied before the
pack lacquer - I think it looks excellent. You need to use a hairdryer to
soften the tape to make it bend round corners. It's not an easy job
#838 If you right-click on the file name you will be given the option
of "Save target as" which will give you the opportunity to save
the .jpg or .gif file to your hard drive, the best place will
probably be under "My documents" or one of its sub directories such
as "My pictures" or "My photos" so you can find them again easily.
Click "Save" and the job's done, then you can open the files offline
at your leisure using most graphics applications or simply double
click to open with your default application. From there you can
usually print the document as you would normally.
#839 Try now, I have saved it as a Word file - 800K, so it will take a
while to
download if you use dial up.
#910 is there a list of the 1008 genuine thruxtons worldwide.
#920 Ray Thurston of the Woburn Centre keeps a Thruxton Register.
#921 For a good few months now I have disabled the files attachment
facility on
our e group, so if you find a mail from the group with a file attached it's
probably dodgy.
#997 I have heard the term 2 pack paint but here in Canada it is
not a term we use. I assume it means paint and hardner but really I
don't know. Could anyone help me to understand this term and to
perhaps lead me to find the correct blue and silver colour for the
67 VMT. Paint codes useful in North American would be good. Also
what recommendations do you have for the type of paint to use, and
lastly what is the best method to deal with the tank transfers. It
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seems the 40 VMT's that came to Canada were delivered with this
colour scheme.
#998 What seem simple jobs never are are they? I've spent a while this
trying to remove the closing/fastening screw from the toolbox lid so I can
with a bit of rust…….
#1000 The knob assembly comprises 5 items, and is assembled in the lid.
There is the
knurled knob, the stud, two plain washers amd a double coil spring washer.
latter three are placed on the reduced diameter outer end of the stud, one
plain inside the lid and the other washers outside the lid, and the knob is
either screwed on, or pressed on, and locked. It is not intended to come
#1014 Martin Arscott sells self adhesive transfers at GBP5 a pair. Tel
862966 or mail [email protected] I have used both varnish and waterslide
transfers. Varnish are very difficult to apply, and waterslide leaves a
slightly white finish. For your tank I would recommend two pack (see )successfully as you can
repolish it. I have painted four Velo tanks with two pack, I recommend a
clear lacquer over both the paint, transfers and lines - sorry I don't have
the correct paint codes
#1031 Tom Ross <[email protected]>" <[email protected]> .
Dai, everyone, I have the VOCNA copy (thanks Dennis Q.) of invoices
for Velocettes received by Lou Branch, the US distributor, from 1950
to 1960. Any member with a machine from this source and time period
is welcome to ask for a copy, scramblers were particulary popular.
#1036 I am always envious when I see Velocettes with polished timing covers
and gearbox end covers.
My timing cover is smooth but ther gearbox is a very rough casting.
Has anyone any useful advice on how to improve the gearbox
appearance. I am not necessarily after a mirror finish but at least
an improvement on what it currently is.
#1037 It basically requires lots of elbow grease but have a look at it has a wealth of info on the
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##1039 It basically requires lots of elbow grease but have a look at it has a wealth of info on the
#1050 first q is , are there many velo owners in the San Francisco area and
you need parts how do you come by them.
#1074 I have a Thruxton motor and a (real) bolt-up Manx rolling chassis I
am building into a Norcette/Velton or whatever - a nice bike anyway.
I am using std Velo transmission etc. One of the rules of the build
is that I dont cut any of the frame (or the Velo bits either).
I have restored/built a lot of bikes but would be pleased to hear
from anyone who has done something like this - I think my only real
concern is getting the engine plates right - i.e. getting the
balance/weight distribution correct. I am working from pics of Bill
Swallows old racer as a crude guide, but that frame was heavily
modded so its only a very rough guide.
I am happy to experiment with different plates - thats part of the
fun - but it would be good to hear of anyone elses experience in
this respect.endmis
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#15 Got a few Velo bits from Grove Classic Motorcycles in England, pretty fast
service: [email protected]
#32 I have been in touch with Ed Gilkison and Geoff Blanthorn, and Dave Smith of Dave Smith
Classic Motorcycles, and they are all good fellows to deal with, whether for available parts or good
#160 Sorry for the delay in getting back to you. Below you are the telephone numbers of UK suppliers
of reconditioned mags, I have not used them so I can make no recommendations. Some may only
provide exchanges.
Dave Lindsley +44 (0) 1706 365838
FTW +44 (0) 114233 6269
Independent ignition supplies +44 (0) 1237 475986
Dynamos only P Dunn +44 (0) 1782 856839
#248 I agree with Dai, Seymour's are wonderful people.
#273 If you want to update with a practical solution for everyday use with a modern
carb I would suggest contacting Phil Allen at:
Allens [email protected], Unit B9, Moorbridge Road, Bingham, Notts
Tel 01949 836733
Fax 01949 836734
Open Monday to Friday 9 to 5, Saturday by prior apointment
Phil has Mikuni alternatives with suitable base setup and a good supply of
spares should they be needed.
#274 Anybody contacting Allens, please don't ask for Phil, he recently died of a
heart attack. The business is still being run by his wife Jane and Phil's
assistant Darren. They still know what they are doing/talking about and have
plenty of stock.
#279 rebuilding the Lucas magneto? I have sent off the armature to Independant Ignition Supply in
Devon(?) They seem like competent folks, and their prices are quite fair
#280 sent my magneto
to him which he extensively overhauled. I was impressed with the
service and how helpful he was. Mine has been running perfectly for
the last year.
I would give him a call and discuss your concerns. His number is
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Tel +44 (0)1706 365838
#342 I have run an Alton alternator now for about 4 years and have had no
problems. It does come with a hefty fully encased regulator unit and
the strap will have to be changed for a more substantial type. Their
is a strong magnetic pull compared to a dynamo I also run it with a
club supplied tooth belt.The only critcism if any is the vents on the
body (water ingestion maybe on the exposed posistion on a Velo).
Moreover, as it was designed for the Vincent some maybe supplied with
a parallel keyed shaft for a magdyno not a taper a la Velo.They are
expensive but are a clever bit of design also by the time you've had
a dynamo overhauled bought a new electronic regulator you're half way
to buying the Alton with 150 watts
#346 Don't know if people are generally aware of this, but a modern
alternative self-generating magneto ignition system is being
developed by Rex Caunt Racing using the BT-H trade mark. The results
can be seen at or by following
the links from
Rex makes ignition systems for classic racers which are considered to
be one of the best. The magnetos are not cheap, estimated price on
his web site is £500, but it might be worth it for a reliable system
and a weight saving of over 3/4lb over a Lucas K1F. Base mounted
units already in production for AJS/Matchless etc are available with
a choice of 2 advance curves built in so I would guess that they can
be run without an ATD - another positive point for those who want to
run a tacho drive from the timing cover but don't want the hassle of
manual advance.
#370 By the way, while Ken Gardner has retired and sold his business to Mike Fotherby (who
appears to be doing a great job) Ken has retained stocks of Velo two stroke parts mainly for his own
restorations, his number is 01608 684904. Please respect his retirement and only use him in
#392 I recommend the following supplier of parts. Mike is in the Woburn group of
the VOC.
John Shipman
Mike Fotherby
Grove Classic Motorcycles Ltd
Tel: (+44) 01582 873066
Fax: (+44) 01582 873654
[email protected] [yes, "" is correct!].
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#408 (suspension unit rubbers) If you can provide a pattern or drawing, Hill’s Rubber Company in the
should be able to make them for you or grind down the VSL ones. They are not
normally very expensive; telephone number is =44 (0) 1189 580535.
#409 I think this is a spare that is still available.
Contact Seymours' (01 844 212 277) or other dealers.0
#352 For the colour schema Velocette had their own identification which gave the
original polychromatic Silver Grey of the 150 the no. 1.
For to get this colour I recommend to contact
Bullers End
43, Bradford Lane
WS1 3LU.
#472 Anybody know of a good machine shop (preferably around Glasgow /
Edinburgh)? I have got the engine in my U stripped, and now need to
get a new bottom end bush made
#474 You could try Owen’s Velocette drawing office for original copies of the
drawings of the bushes if you want a machine shop to make them up. (Also
remember to check the wear on the shaft)
#475 have a look at the Scottish bit on the VOC web site.
There are a couple of people listed there who might be able
to help you.
#478 Paul of Grangemouth Ship Repair uses Smith Electrical (Don't worry about the
Contact Eddie Williamson Tel: 01 324 888 020.
#485 Here are some useful suppliers for Velocettes:
Control cables: Johnson's Cables Tel: 01844 237479
Wheels: Essex Wheels Tel: 01787 460230
Speedos: Jim ??? Tel: 01604 861930
Tyres and tubes: John Lovick Tel: 01760 722886
Number plates: P Mellor Tel: 01484 653559
Chrome plating: S B Products Tel: 01733 266138
Brake relining: Terrac Engineering Tel: 01604 647655
Magneto and dynamo repairs: Dave Lindsley Tel: 01706 365838
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Spares: Grove Classics: Tel: 01582 873066
Spares: Veloce Spares Ltd. Fax: 0116 275 2703
Painting: Lewis and Templeton Tel: 024 7660 4663
Transfers: Robert Derrick Tel: 01454 260596
Service manuals and other books: Don Mitchell Tel: 0116 277 7669
Sprockets: Sprockets Unlimited Tel: 01386 831341.
#520 Martyn Bratby can be found at:No1 The Coachouse Works
Limepit Lane
WS12 4PA
Tel 01543 572583
He does Velocette clutch plate inserts and replacement clutch friction
plates (also a vast array of springs and reconditions carburrettors).
#642 I have been trying to contact Goodman Engineering, Evesham, regarding
their verification service for several days - telephone is out of
order and e-mails are returned "unknown address" - any information
about them please??
#643 Simon Goodman sold his business to Grove Classic Motorcycles about three
months ago. Mike Fotherby's number is 01582 873066.
#728 Does anyone know of a good supplier of s/s tube offcuts in lengths
suitable to make my own tiddly mudguard stays-1/2" & 3/4" o/d ?
#729 Metal Supermarkets
At an address near you
#730 Mail Order Metals in Nottingham
Tel 0115 9748211
Fax 0115 9745469
Email [email protected]
Web site
can supply the S/S tube
#796 The best source of the unique parts is in the USA try this guy
[email protected] ( Olav Hassell ) he is most knowledgeable
and an avid scrounger / source of Scrambler parts.
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#809 Re parts sourc in the usa;
Ed Gilkison has quite a lot of stuff, but can be very slow in delivery. If
he doesn't have it, often he will refer you to another who might;
[email protected]
#815 Olav, I've found
him very knowledgeable and willing to 'work' at sourcing parts for you
and he's in virtually the only place where Scrambler spares can be found.
If you go back to Fishtail # 319 page 48 you'll find all his contact
#830 Dave Smith is at 815 254 3998 ; [email protected] He used to be the
exclusive dealer for Goodman's here in the US, and is a valuable resource
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