Maintaining the
Teledyne
Bendix D-3200
series Magneto
• GENERAL: Good standard shop practices and
safety precautions should be observed at all
times to avoid injury to personnel and damage to
equipment.
• This discussion is not intended to replace the
information contained in the Teledyne Service
Support manual and the Teledyne manuals must
be used while actual maintenance is performed
on the magneto.
Recommended Maintenance
Intervals
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First 25 hour: Inspect Contact Assemblies
100 Hour: Inspect Contact Assemblies
500 Hour: Inspect IAW TCM 500Hr. Check
TCM Recommends 4 year overhaul
intervals
Description and Specs.
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The magneto used on F series
Enstrom helicopters is the D4LN3200 manufactured by Teledyne
Continental Motors, Aircraft
Products, Mobile AL.
D - Dual type ignition unit
4 - Number of engine cylinders
L - Direction of rotation from the
drive end
N - Manufactured by TCM
3200 Shower of sparks
starting system
Some C model helicopters use an
impulse coupling rather than the
shower of sparks.
Troubleshooting Tips
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If the springs come out of the distributer block when removing
the magneto cover, there is a special tool that is used to reinsert them. Use some silicone or Teflon spray on the
insulators before installing the cover to prevent them from
sticking in the distributer block.
If there is a significant split between the opening of the right
and left magneto points, or if the magneto to engine timing
has slipped, do not “bump” the mag to correct the timing.
Check the point gap inside the mag to determine if the points
are closing up.
If the engine kicks back during start, particularly just after the
magneto has been installed, remove the retard “P” lead and
check that it is making contact with the copper tang inside the
mag cover.
If the contact assemblies (points) close up during use, inspect
the cam followers closely for damage to both sides of the cam
follower. (See slide 10)
RIGHT CONTACTOR
DATA PLATE
RIGHT MAGNETO COIL
WIRE
RETARD CAM
RETARD CONTACTOR
RETARD CONTACT
FLEXIBLE TAB TERMINAL
LEFT MAGNETO
CONTACTOR
Shower of Sparks
Maintenance Procedures
• Inspection of contact assemblies.
• Adjust contact gap & timing / install new
contacts.
• Install magneto and time to engine.
Inspection of contact assemblies
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Remove the cover
assembly.
Turn engine fan until
points are fully open.
Inspect the contacts for
condition.
Inspect cam followers for
condition.
Check for point gap.
Contact condition
1.
2.
3.
4.
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If gap is less than 0.012, remove
magneto and adjust or replace
points.
Inspect cam follower carefully to
determine the cause of the wear.
If the contact surface shows evidence
of burning, or if the cam follower
shows evidence of melting where it
pushes on the contact spring, the
capacitor needs replacement.
If the cam follower shows excessive
wear or melting where it contacts the
cam, the causes can be:
Lack of lubrication on felt.
Problems with cam.
Bearing in distributor block
running hot.
3
4
This is a cam
follower that
has melted
against the
contact
spring due to
a faulty
capacitor (3)
Replacing Contacts
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Part numbers:
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Right side contact: 10382585
Left side contact: 10400184
Capacitor: 10-400575
Distributer springs:10-50737
• Begin by removing both sets of
contact points, and both cams.
•The bottom cam can be removed
by inserting the blade of a flat
screw driver between the bearing
and the cam, and prying it off.
Install Right Mag Points
•Install the bottom cam with an
appropriate screw and washer
and position it so that the
points will be resting on the
cam lobe. At this point in the
procedure, the positioning of
the cam is not important
except that the points need to
be fully open.
•Install the right magneto
points and set the gap to .016
•Use a business card or
equivalent to clean the oil from
the contact surfaces and wipe
excess oil from the cam
followers with a clean, lint free
cloth.
Set Internal Timing
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Position the rotating magnet so
that the ‘C’ is adjacent to the
mark cast into the inside of the
housing on the top of the
magneto, the mag is in the
neutral position, and the two
chamfered teeth are visible in
the windows in the ends of the
magneto.
NOTE: The impulse magnetos
are time to the K and not to the
C.
Time right contactor
opening
•Loosen the cam from its
tapered shaft and rotate
the cam until the points
open when the L is
exactly adjacent the
marker on the inside of
the case.
•Snug the cam retaining
screw so that the cam will
not rotate on the shaft.
Install & Time the Left side Contactor Assy.
Main contactor cam
Left side main
contactor (points)
Retard cam
Left side retard points
• Now Install the left side
contact assembly on to the
distributer block and install
the retard cam overtop of
the main contactor cam.
Adjust the left main
contact so that it opens
simultaneously with the
right side contact.
Check the Synchronization of the Contactors
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Check the gap on both the main
and retard contacts. Both contact
gaps must be .016 plus or minus
.004
If they are not, it is permissible to
carefully bend the steel uprightframe of the contact assembly
untill both gaps are within limits.
If the upright-frame is adjusted by
bending it, the opening of the left
side main contactor opening will
have to be re-synchronized with
the right contactor assembly
opening.
If the contact openings cannot be
synchronized with the gaps within
limits, the contacts will need
replacement.
Retard Timing
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Install the timing light lead
onto the retard contactor.
Electronic timing lights may
require clipping the coil wire
under the timing light lead to
operate.
Set the retard points to open
when the pointer inside the
magneto housing is exactly
adjacent the 20 degree
mark on the rotating
magnet.
This adjustment is made by
rotating the retard cam until
the points open at the
correct time.
Torque the hold down
screws to 21 to 25 inch lbs.
Retard contact clip
20 degree retard position
Installing the
Magneto on the
Engine
Set the engine at the firing
position for #1 cylinder
.
•Remove the bottom spark plug
from #1 cylinder.
•Pull the engine through in the
direction of rotation untill
compression is felt at the spark
plug hole.
•Set the flywheel to the 20 degree
advance position
Set the Magneto at the Firing
Position for #1 Cylinder
•Set the rotating magnet so
that the C is at the pointer
inside the magneto, the 2
chamfered teeth are in the
windows at the two opposite
ends of the magneto, and the
magneto is in the neutral
position.
•Install the plugs in the
housing. The vented plugs
must not be installed in the top
position. Install them in the
side plug positions.
Check the Alignment of the Drive
Gear
•On older magnetos, the drive adapter
may be horizontal while on newer mags,
it is vertical
•Check that the alignment of the gear
adapter in the engine is at the same
relative angle as the one on the mag.
•Occasionally the gear adapter in the
engine will come out while removing the
magneto.
•The gear adapter has an odd number of
gear teeth and if the alignment is just a
little off, it can be pulled out and
reinstalled 180 degrees off which will help
align the gear adapter to the magneto.
Install the Magneto on to the
Engine
•Install the magneto
on the engine.
•Install the hold-down
clamps, washers and
nuts.
•Tighten the nuts so
that they are snug,
but so the magneto
can still be swiveled.
Time the main points to open at 20
degrees BTC (Before Top Center)
•Attach the timing light to the main
contactors.
•Turn the magneto until the points
just open when the flywheel is at
the 20 degree BTC position.
•Tighten the magneto hold-down
nuts.
•Re-check the firing position by
rotating the fan backwards and
then forward until the points just
open. Check that the marks on
the flywheel are in the proper
position.
Checking the retard timing
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Attach the timing light to the
retard points. (copper tang)
Turn the engine with the fan until
the timing light indicates that the
retard points have just opened.
Check the flywheel to verify that
the points have just opened when
the flywheel is ½ tooth after TDC.
If adjustment is required, loosen
the retard cam attach screw and
using your fingers, or a pair of
snap ring pliers, turn the retard
cam until the points just open
when the mark on the starter is ½
tooth after TDC.
Re-torque the cam attach screw.
(If your engine starts when the
starter button is released, it is
most likely timed at TDC which is
too advanced.)
Close it up
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Torque the slotted contact screws and the cam retention screw to 21-25 in
lbs.
Connect the coil wires to the contact terminals.
Spray the insulating sleeves with MS-122DF TFE (Teflon dry lubricant
release agent) to prevent the insulators from sticking in the distributer block.
Install the cover and torque corner screws to 30 – 35 in lbs.
Look down into the retard ‘P’ lead socket and verify that the copper
contactor is positioned so that the ‘P’ lead will make firm contact with it
when it is inserted into the socket. Is possible to distort the copper contact
with the cover while installing it.
Install the ‘P’ leads.
Check that the helicopter has been completely assembled and check the
magneto operation.