STIH)
STIHL BG 56, 66, 86, SH 56, 86
2008-01
Contents
1.
2.
Introduction
Safety Precautions
2
Specifications
4
3.1
3.2
3.3
3.4
Engine
Fuel System
Ignition System
Tightening Torquese
4
4
4
5
Troubleshooting
Rewind Starter
44
7.1
7.2
General
Removing and
Installing
Pawls
ErgoStart
Rope Rotor
Starter Rope / Grip
Tensioning the
Rewind Spring
Replacing
the Rewind Spring
44
7.3
7.4
7.5
7.6
7.7
7
4.1
4.2
4.3
4.4
4.5
Rewind Starter
Fan
Ignition System
Carburetor
Engine
7
8
9
11
14
5.
Engine
15
5.1
5.7
5.8
5.8.1
Muffler / Spark
Arresting Screen
Leakage Test
Preparations
Vacuum Test
Pressure Test
Oil Seals
Removing and
Installing the Engine
Removing and
Installing the Cylinder
Crankshaft
Removing and
Installing
Bearings / Crankshaft
Piston
Piston Rings
6.
Ignition System
31
10.
6.1
6.1.1
Ignition Module
Removing and
Installing
Ignition Timing
Testing
the Ignition Module
Spark Plug Boot
Flywheel
Short Circuit Wire
Testing
Removing and
Installing
Ground Wire
Stop Switch
31
10.1
10.2
10.3
5.5
RA_296_01_01_01
5.6
5.6.1
6.2
6.3
6.4
6.5
6.6
6.6.1
6.6.2
6.6.3
6.6.4
41
7.
7.8
5.2
5.2.1
5.2.2
5.2.3
5.3
5.4
Ignition System
Troubleshooting
3
3.
4.
6.7
44
44
45
46
47
49
50
8.
Repairing AV System
SH 86, 86 C,
BG 66C, 86, 86 C
52
8.1
Removing and
Installing
Handle
SH 86, 86 C,
BG 66C, 86, 86 C
53
9.
Control Levers
55
9.1
9.2
21
24
9.3
Switch Positions
Setting Lever
SH 86, 86 C,
BG 66C, 86, 86 C
Throttle Trigger
SH 56, 56 C,
BG 56, 56 C, 66
Throttle Trigger
SH 86, 86 C,
BG 66C, 86, 86 C
55
19
8.2
15
16
16
17
17
18
24
27
28
30
31
33
33
34
35
36
36
37
40
40
9.4
10.3.1
10.4
10.4.1
10.4.2
10.4.3
10.4.4
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.4.5 Adjusting Screws
10.5
Adjusting the
Carburetor
10.5.1 Basic Setting
10.5.2 Standard Setting
10.6
Throttle Rod
10.7
Removing and
Installing
the Spacer Flange
10.8
Tank Vent
10.8.1 Testing
10.8.2 Removing and
Installing
10.9
Fuel Intake
10.9.1 Pickup Body
10.9.2 Fuel Hoses
10.9.3 Fuel Tank Cap
11.
67
68
68
69
70
71
72
72
73
73
73
74
75
Blower and Vacuum
Attachment
76
57
Intake Screen
76
Fanwheel
77
Removing and Installing
the Fan Housing
SH 56, 56 C,
BG 56, 56 C, 66
78
11.3.1 Removing and Installing
the Fan Housing
SH 86, 86 C,
BG 66C, 86, 86 C
78
11.3.2 Removing and Installing
the Handle Housing
SH 86, 86 C,
BG 66C, 86, 86 C
79
11.4
Blower Tube
BG Models
79
11.5
Elbow
SH Models
80
11.6
Suction Tube
SH Models
80
Fuel System
59
12.
Air Filter
Baffle / Filter Housing
Removing and
Installing the
Carburetor
Leakage test
Servicing the
Carburetor
Metering Diaphragm /
Manual Fuel Pump
Inlet Needle
Pump Diaphragm
Throttle Lever /
Rotary Knob
59
60
52
55
56
11.1
11.2
11.3
13.
Special
Servicing Tools
81
Servicing Aids
83
61
62
62
62
64
64
66
q
© ANDREAS STIHL AG & Co. KG, 2008
1
1.
Introduction
This service manual contains
detailed descriptions of all the repair
and servicing procedures specific to
this power tool.
You should make use of the
illustrated parts lists while carrying
out repair work. They show the
installed positions of the individual
components and assemblies.
Refer to the latest edition of the
relevant parts list to check the part
numbers of any replacement parts.
The special tools mentioned in the
descriptions are listed in the chapter
on "Special Servicing Tools" in this
manual. Use the part numbers to
identify the tools in the
"STIHL Special Tools" manual. The
manual lists all special servicing
tools currently available from
STIHL.
Symbols are included in the text and
pictures for greater clarity.
The meanings are as follows:
In the descriptions:
A fault on the machine may have
several causes. To help locate the
fault, consult the troubleshooting
charts for all assemblies and
systems in this manual and the
"STIHL Service Training System".
Refer to the “Technical Information”
bulletins for engineering changes
which have been introduced since
publication of this service manual.
Technical information bulletins also
supplement the parts list until a
revised edition is issued.
Always use original STIHL
replacement parts.
They can be identified by the STIHL
part number,
the STIH) logo and the
STIHL parts symbol (
This symbol may appear alone on
small parts.
Storing and disposing of oils and
fuels
Collect fuel or lubricating oil in a
clean container and dispose of it
properly in accordance with local
environmental regulations.
: = Action to be taken as
shown in the illustration above
the text
– = Action to be taken that is
not shown in the illustration
above the text
In the illustrations:
A Pointer
a Direction of movement
b 4.2 = Reference to another
chapter, i.e. chapter 4.2
in this example
Service manuals and all technical
information bulletins are intended
exclusively for the use of properly
equipped repair shops. They must
not be passed to third parties.
2
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
2.
Safety Precautions
If the engine is started up in the
course of repairs or maintenance
work, observe all local and countryspecific safety regulations as well
as the safety precautions and
warnings in the instruction manual.
Gasoline is an extremely flammable
fuel and can be explosive in certain
conditions.
Always wear suitable protective
gloves for operations in which
components are heated for
assembly or disassembly.
Improper handling may result in
burns or other serious injuries.
Do not smoke or bring any fire,
flame or other source of heat near
the fuel. All work with fuel must be
performed outdoors only. Spilled
fuel must be wiped away
immediately.
Always perform leakage test after
working on the fuel system and the
engine.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
3
3.
Specifications
3.1
Engine
BG 56, SH 56
BG 66, BG 66 C
BG 86, SH 86
Displacement:
Bore:
Stroke:
Engine power to ISO 7293:
Max. permissible speed
(with nozzle):
Idle speed:
Engine leakage test
under vacuum:
at gauge pressure:
27.2 cm3
34 mm
30 mm
0.70 kW (1.0 bhp)
27.2 cm3
34 mm
30 mm
0.60 kW (0.8 bhp)
27.2 cm3
34 mm
30 mm
0.8 kW (1.1 bhp)
6800 rpm
2500 rpm
5800 rpm
2500 rpm
7200 rpm
2500 rpm
3.2
Carburetor leakage
test at gauge
pressure:
Operation of tank
vent at gauge
pressure:
Fuel:
0.5 bar
as specified in instruction manual
Air gap between
ignition module and
fanwheel:
0.15 ... 0.30 mm
3.3
Fuel System
Ignition System
0.5 bar
0.5 bar
Spark plug
(suppressed):
Electrode gap:
4
0.8 bar
NGK CMR 6 H
0.5 mm
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
3.4
Tightening Torquese
DG and P (Plastoform) screws are used in polymer and light metal components. These screws form a
permanent thread when they are installed for the first time. They can be removed and installed as often as
necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is
observed.
For this reason it is essential to use a torque wrench.
Fastener
Thread size
For component
Torque
Remarks
Nm
Nut
Screw
Screw
Screw
Screw
Nut
Screw
Screw
Screw
Screw
M5
P 5x18
D 5x24
D 5x24
D 5x24
M 8x1 L
P 5x18
P 5x18
P 5x18
P 5x18
Screw
Screw
Screw
Nut
Screw
Screw
D 5x60
D 5x20
D 5x20
M 8x1
D 5x20
D 5x20
M 10x1
D 4x18
D 5x20
Screw
Screw
Filter housing/carburetor/spacer flange
Fan housing, outer/inner
Fan housing, inner/crankcase
Fan housing, inner/engine pan
Fan housing, inner/cylinder
Fanwheel/crankshaft
Handle/cover/plug
Handle/handle frame/plug
Handle molding/fran housing, inner
Handle molding/handle/handle frame/
plug
Engine pan/crankcase/cylinder
Fan housing/spiral housing
Muffler/cylinder
Flywheel/crankshaft
Spiral housing/crankcase
Spiral housing/engine pan
Spark plug
Ignition module/cylinder
Spacer flange/cylinder
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
3.5
3.0
8.0
8.0
8.0
17.0
3.0
3.0
3.0
3.0
9.0
6.0
9.0
17.0
6.0
6.0
12.0
3.5
6.0
1)
5
Remarks:
1) Degrease crankshaft/flywheel and mount oil-free
Use the following procedure when refitting a DG or P screw in an existing thread:
Place the screw in the hole and rotate it counterclockwise until it drops down slightly.
Tighten the screw clockwise to the specified torque.
This procedure ensures that the screw engages properly in the existing thread and does not form a new thread
and weaken the assembly.
Power screwdriver setting for polymer: DG and P screws max. 500 rpm
Do not use an impact wrench for releasing or tightening screws.
Do not mix up screws with and without binding heads.
6
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
4.
Troubleshooting
4.1
Rewind Starter
Condition
Cause
Remedy
Starter rope broken
Rope pulled out too vigorously as
far as stop or over edge, i.e. not
vertically
Fit new starter rope
Normal wear
Fit new starter rope
Very dirty or corroded
Clean or replace rewind spring
Insufficient spring tension
Check rewind spring and increase
tension
Rewind spring worn
Fit new rewind spring
Starter rope cannot be pulled out
far enough
Spring overtensioned
Check rewind spring and reduce
tension
Starter rope can be pulled out
almost without resistance
(crankshaft does not turn)
Guide peg on pawl or pawl itself is
worn
Fit new pawl
Pawl spring fatigued
Fit new pawl spring
Models with ErgoStart
Spring broken or fatigued
Fit new ErgoStart spring
Starter rope is difficult to pull or
rewinds very slowly
Starter mechanism is very dirty
Thoroughly clean complete starter
mechanism
Lubricating oil on rewind spring
becomes viscous at very low
outside temperatures (spring
windings stick together)
Coat rewind spring with a little
standard solvent-based degreasant
(containing no chlorinated or
halogenated hydrocarbons), then
pull rope carefully several times
until normal action is restored
Starter rope does not rewind
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
7
4.2
Fan
Always switch off the engine before
working on the fan.
Condition
Cause
Remedy
No suction
Fanwheel loose
Tighten down fanwheel nut firmly
Fanwheel blocked
Clean fan housing
Catcher bag full
Empty the catcher bag
Fan outlet blocked
Clean fan housing and outlet
Fanwheel worn or too many blades
broken
Fit a new fanwheel
Intake screen very dirty
Clean intake screen and fan
housing
Fanwheel loose
Tighten down fanwheel nut firmly
Fanwheel worn or too many blades
broken
Fit a new fanwheel
Shredder blade loose or worn
Tighten down or replace the
shredder blade
Poor suction
Poor blowing performance
Leaves are not properly shredded
8
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
4.3
Ignition System
Exercise extreme caution while
carrying out maintenance and
repair work on the ignition system.
The high voltages which occur can
cause serious or fatal accidents.
Condition
Cause
Remedy
Engine runs roughly, misfires,
temporary loss of power
Spark plug boot is loose
Press boot firmly onto spark plug
and fit new spring if necessary
Spark plug sooted, smeared with oil Clean the spark plug or replace if
necessary.
Fuel/oil mixture
– too much oil
Use correct mixture of fuel and oil
Incorrect air gap between ignition
module and flywheel
Set air gap correctly
Flywheel is damaged or pole shoes
have turned blue
Install new flywheel
Ignition timing out of adjustment,
flywheel warped, key in flywheel
sheared
Install new flywheel
Flywheel magnetization weak –
pole shoes have turned blue
Install new flywheel
Irregular spark
Check operation of stop switch and
ignition module.
Faulty insulation or break in ignition
lead or short circuit wire. Check
ignition lead/ignition module and
replace ignition module if
necessary.
Check operation of spark plug.
Clean the spark plug or replace if
necessary.
Also refer to carburetor and engine troubleshooting.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
9
Condition
Cause
Remedy
No spark
Spark plug faulty
Install new spark plug
Faulty insulation or short in short
circuit wire
Check short circuit wire for short
circuit to ground
Break in ignition lead or insulation
damaged
Check ignition lead, replace ignition
module if necessary
Ignition module faulty
Install new ignition module
10
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
4.4
Carburetor
Condition
Cause
Remedy
Carburetor floods; engine stalls
Inlet needle not sealing
– Foreign matter between valve
seat and sealing cone or sealing
cone worn
Remove and clean the inlet needle,
clean the carburetor
Inlet control lever sticking on
spindle
Clean the inlet control lever or
replace if necessary.
Helical spring not located on nipple
of inlet control lever
Remove the inlet control lever and
refit it correctly
Perforated disc on diaphragm is
deformed and presses constantly
against the inlet control lever
Fit a new metering diaphragm
Poor acceleration
Setting of low speed screw too lean Check basic carburetor setting,
correct if necessary
Setting of high speed screw too
lean
Check basic carburetor setting,
correct if necessary
Inlet needle sticking to valve seat
Remove inlet needle, clean and
refit
Diaphragm gasket leaking
Fit new diaphragm gasket
Metering diaphragm damaged or
shrunk
Fit a new metering diaphragm
Spacer flange damaged
Install new spacer flange
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
11
Condition
Cause
Remedy
Engine will not idle, idle speed too
high
Throttle shutter opened too wide by
idle speed screw LA
Reset idle speed screw LA
correctly
Oil seals/engine leaking
Seal or replace oil seals/engine
Throttle shutter stiff or torsion
spring on throttle shaft fatigued or
broken
Free off throttle shaft or install new
carburetor
Idle jet bores
or ports blocked
Clean the carburetor
Setting of low speed screw too rich
or
too lean
Reset low speed screw L correctly
Setting of idle speed screw
incorrect – throttle shutter
completely closed
Reset idle speed screw LA
correctly
Engine stalls at idle speed
12
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Condition
Cause
Remedy
Engine speed drops quickly under
load – low power
Air filter dirty
Clean air filter or replace if
necessary
Throttle shutter not opened fully
Check rod
Tank vent faulty
Replace tank vent
Fuel pickup body dirty
Install new pickup body
Fuel strainer dirty
Clean fuel strainer in carburetor,
replace if necessary
Leak in the fuel suction hose
Fit new fuel suction hose
Setting of high speed screw H too
rich
Check basic carburetor setting,
correct if necessary
Main jet bores or ports blocked
Clean or replace the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
13
4.5
Engine
Always check and, if necessary,
repair the following parts before
looking for faults on the engine:
- Air filter
- Fuel system
- Carburetor
- Ignition system
Condition
Cause
Remedy
Engine does not start easily, stalls
at idle speed, but operates normally
at full throttle
Oil seals in crankcase damaged
Replace the oil seals
Engine leaking or damaged
(cracks)
Seal or replace the engine
Piston rings worn
Fit new piston rings
Muffler / spark arresting screen
carbonized
Clean the muffler (inlet and
exhaust), replace spark arresting
screen, replace muffler if necessary
Air filter dirty
Replace air filter
Fuel suction hose kinked or torn
Fit new hose or position it free from
kinks
Tank vent faulty
Check the tank vent and replace if
necessary.
Insufficient cylinder cooling. Air
inlets in fan housing blocked or
cooling fins on cylinder very dirty
Thoroughly clean all cooling air
openings and the cylinder fins
Engine does not deliver full power
or runs erratically
Engine overheating
14
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
5.
Engine
5.1
Muffler / Spark Arresting
Screen
Spark arresting screen
Always check and, if necessary,
repair the fuel system, carburetor,
air filter and ignition system before
looking for faults on the engine.
1
296RA002 TG
– Remove the fan housing, b 7.2
: Unscrew the stub with spark
arresting screen (1).
1
296RA000 TG
– Clean the stub with screen (1) or
replace if necessary.
– Reassemble in the reverse
sequence.
296RA004 TG
1
– Troubleshooting, b 4.5
– Insert the screws trough the
holes in the muffler.
: Push the gasket (1) over the
screws – the gasket is held in
position.
1
: Take out the screws (arrows).
296RA003 TG
296RA005 TG
– Remove the muffler (1), check
and replace if necessary.
: Inspect and clean the sealing
faces (arrows), b 13
296RA001 TG
1
: Remove the gasket (1).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
– Carefully place the muffler (1) in
position.
: Line up the screws (arrows) and
check the position of the gasket.
– Insert screws (arrows) and
tighten them down firmly.
– Install the fan housing, b 7.2
– Tightening torques, b 3.4
15
: Fit the spark plug (1) and tighten
it down firmly.
Defective oil seals and gaskets or
cracks in castings are the usual
causes of leaks. Such faults allow
supplementary air to enter the
engine and upset the fuel-air
mixture.
– Tightening torques, b 3.4
1
296RA008 TG
Leakage Test
This makes adjustment of the
prescribed idle speed difficult, if not
impossible.
Check that the gasket (1) is in
position.
Always perform the vacuum test
first and then the pressure test.
296RA000 TG
1
Moreover, the transition from idle
speed to part or full throttle is not
smooth.
: Loosen the screws (arrows).
The engine can be checked
thoroughly for leaks with the pump
0000 850 1300.
– Lift the muffler (1).
3
O 16
Preparations
1
296RA007 TG
296RA006 TG
1
– Remove the fan housing, b 7.2
– Pull the boot off the spark plug.
: Unscrew the spark plug (1).
– Set the piston to top dead center.
This can be checked through the
spark plug hole.
16
Test flange (1) 1128 850 4200 can
be modified as shown above.
: Fit the sealing plate (1)
0000 855 8106 between the
cylinder exhaust port and muffler
and tighten down the screws
moderately.
The sealing plate must completely
fill the space between the two
screws.
1
296RA010 TG
5.2.1
296RA009 TG
5.2
: Fit the test flange 5910 850
4200 (1).
– Remove the carburetor, b 10.3
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
5.2.3
Pressure Test
1
5.2.2
: Push ring (1) to the left.
: Operate the lever (2) until the
pressure gauge (arrow) indicates
a vacuum of 0.5 bar.
Vacuum Test
Oil seals tend to fail when subjected
to a vacuum, i.e. the sealing lip lifts
away from the crankshaft during the
piston's induction stroke because
there is no internal counterpressure.
A test can be carried out with pump
0000 850 1300 to detect this kind of
fault.
296RA012 TG
: Fit the nuts (arrows) and tighten
them down firmly.
1
296RA013 TG
296RA011 TG
2
If the vacuum reading remains
constant, or rises to no more than
0.3 bar within 20 seconds, it can be
assumed that the oil seals are in
good condition.
However, if the pressure continues
to rise (reduced vacuum in the
engine),
the oil seals
must be replaced, b 5.3.
Carry out the same preparations as
for the vacuum test, b 5.2.2
– Always carry out the vacuum test,
b 5.2.2, before the pressure
test.
: Connect pressure hose (1) of
pump 0000 850 1300 to nipple
(arrow).
– After finishing the test, push the
ring to the right to vent the pump.
1
296RA012 TG
– Continue with pressure test,
b 5.2.3
: Connect suction hose (1) of
pump 0000 850 1300 to nipple
(arrow).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
17
5.3
Oil Seals
2
It is not necessary to disassemble
the engine to replace the oil seals.
Ignition side
1
– Remove the fan housing, b 7.2
– Remove the flywheel, b 6.5
: Push ring (1) to the right.
– Apply a thin coating of sealant to
the outside diameter of the oil
seal, b 13
– Slip the oil seal, closed side
facing outwards, over the
crankshaft stub.
1
296RA015 TG
: Operate the lever (2) until the
pressure gauge (arrow) indicates
a pressure of 0.5 bar. If this
pressure remains constant for at
least 20 seconds, the engine is
airtight.
– If the pressure drops, the leak
must be located and the faulty
part replaced.
To find the leak, coat the suspect
area with oil and pressurize the
engine. Bubbles will appear if a leak
exists.
– After finishing the test, push the
ring to the left to vent the pump –
disconnect the hose.
296RA016 TG
1
296RA014 TG
2
– Free off the oil seal in its seat by
tapping it with a suitable tube or a
punch.
: Apply puller (1) 5910 890 4400
with No. 3 jaws 0000 893 3706.
: Use press sleeve (2)
1121 893 2400 to install the oil
seal (1).
The seating face must be flat and
free from burrs.
– Wait about one minute, then
rotate the crankshaft several
times.
– Degrease the crankshaft taper,
b 13
– Clamp the puller arms.
– Remove the test flange.
– Pull out the oil seal.
– Install the carburetor, b 10.3
Take care not to damage the
crankshaft stub.
– Loosen the muffler and pull out
the sealing plate.
– Clean the sealing face, b 13
– Tighten down the muffler firmly.
– Lubricate sealing lips of new oil
seal with grease, b 13
– Reassemble all other parts in the
reverse sequence.
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
18
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Fan side
5.4
Removing and Installing
the Engine
– Remove the engine, b 5.4
296RA017 TG
1
– Free off the oil seal in its seat by
tapping it with a suitable tube or a
punch.
: Apply puller (1) 5910 890 4400
with No. 3 jaws 0000 893 3706.
296RA020 TG
296RA018 TG
1
: Fit the installing sleeve (1) 4119
893 4600.
– Apply a thin coating of sealant to
the outside diameter of the oil
seal, b 13
The complete engine has to be
removed for access to the piston,
cylinder and crankshaft.
– Slip the oil seal, closed side
facing outwards, over the
installing sleeve.
– Remove the fan housing, b 7.2
– Remove the installing sleeve (1).
– Remove the air filter, b 10.1
– Pull the boot off the spark plug.
– Clamp the puller arms.
– Pull out the oil seal.
– Remove the filter housing,
b 10.2
Take care not to damage the
crankshaft stub.
– Remove the throttle rod, b 10.6
– Lubricate sealing lips of new oil
seal with grease, b 13
1
2
: Use press sleeve (1) 1121 893
2400 to install the oil seal (2).
– Unscrew the spark plug.
296RA019 TG
– Clean the sealing face, b 13
2
1
– Install the engine, b 5.4
– Tightening torques, b 3.4
296RA021 TG
– Wait about one minute, then
rotate the crankshaft several
times.
: Disconnect the short circuit wire
(1) and ground wire (2).
– Put the wires to one side.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
19
Installing
296RA023 TG
: Disconnect the fuel hose (1) and
fuel return hose (2) from the
stubs (arrows) on the connector.
– Remove the fanwheel, b 11.2
1
296RA026 TG
296RA025 TG
1
296RA022 TG
2
– Check the engine and install a
new cylinder, piston, crankshaft
or crankcase if necessary
– after removing the muffler,
ignition module and spacer
flange.
Take care to avoid pinching the
short circuit and ground wires
between the engine and fan
housing.
It is not necessary to disassemble
the engine any further to replace the
oil seals.
: Push the straight crankshaft stub
(1) into the fan housing bore
(arrow).
– Inspect the oil seals and replace
if necessary, b 5.6
– Push the engine against the inner
fan housing.
: Check that the oil seals are
correctly seated
– they must be flush with the
edge (arrow) of the crankcase.
296RA027 TG
: Take out the screws (arrows).
296RA024 TG
1
: Push the complete engine (1) out
of the fan housing.
20
– Position the engine on the inner
fan housing
– the holes in the engine and fan
housing must be in alignment.
: Insert screws (arrows) and
tighten them down firmly.
– Mount the inner fan
housing,b 11.2
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Fit the short circuit and ground wires
in the retainers (arrow).
296RA031 TG
296RA113 TG
2
2
1
: Push the fuel hose (1) and fuel
return hose (2) on to the stubs
(arrows) on the connector.
296RA032 TG
1
– Remove the muffler (1), b 5.1
– Remove the ignition module (2),
b 6.1.1
– Install the air filter, b 10.1
– Reassemble all other parts in the
reverse sequence.
296RA029 TG
– Tightening torques, b 3.4
: Position the ground wire (1) in the
guide (arrow) and push it firmly
on to the connector tag (2).
5.5
Removing and Installing
the Cylinder
Before removing the piston, decide
whether or not the crankshaft has to
be removed as well.
Cylinder installed
To remove the flywheel,
the.crankshaft has to be blocked by
inserting the locking strip in the
spark plug hole.
2
296RA030 TG
1
: Position the short circuit (1) in the
guide (arrow) and push it firmly
on to the ignition module's
connector tag (2).
Cylinder removed
To remove the flywheel, the
crankshaft has to be blocked by
resting the piston on the wooden
assembly block.
1
2
3
296RA033 TG
1
2
– Prepare the puller (1)
5910 890 4400.
: Fit the No. 2 jaws (2)
0000 893 3700.
: Screw the bushing (3)
1108 893 4500 onto the puller's
spindle.
Remove the engine, b 5.4
– Install the throttle rod, b 10.6
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
21
Always use a new cylinder gasket
when re-installing the cylinder.
2
1
1
: Turn the spindle clockwise until
the puller sits tightly.
1
: Carefully lift the cylinder (1)
away.
296RA039 TG
: Apply the puller (1) 5910 890
4400 with the jaws under the
crankcase ribs (arrows) and line
up the spindle (2) so that the
bushing (3) is centered on the
engine pan.
296RA036 TG
296RA034 TG
3
Do not use pointed or sharp-edged
tools for this job.
– Check the cylinder and replace if
necessary.
– Line up the cylinder gasket (1) so
that the tab and cutouts (arrows)
match the contours of the
crankcase.
: Place the cylinder gasket (1) in
position.
Do not overtighten the spindle
because the jaws may slip off or
damage the crankcase ribs.
1
296RA040 TG
296RA037 TG
1
296RA035 TG
: Remove the cylinder gasket (1).
– Inspect the spacer flange (1) and
replace it if necessary – even
very minor damage can result in
engine running problems, b 4.5
296RA038 TG
: Take out the cylinder screws
(arrows).
– Inspect and clean the sealing
face (arrow), b 13
In a new cylinder is installed, the
spacer flange must be transferred
from the old cylinder.
: Take out the screws (arrows).
– Remove the spacer flange (1).
The sealing face must be in perfect
condition. Always replace
components with damaged sealing
faces, b 4.5.
22
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
: Slide the wooden assembly block
(1) 1108 893 4800 between the
piston and crankcase.
– Check the sealing faces on the
cylinder intake and exhaust ports.
The sealing faces must be in perfect
condition. If the sealing faces are
damaged, install a new cylinder.
– Inspect the piston and piston
rings and replace if necessary,
b 5.8
– Lubricate the piston, piston rings
and cylinder wall with oil, b 13
: Use the clamping strap (1)
0000 893 2600 to compress the
rings around the piston.
– Check correct installed position
of rings, b 5.8.1
296RA045 TG
: Inspect and clean the sealing
face (arrow) and remove any
gasket residue, b 13
: Align the cylinder so that the
recess in the cylinder engages
the projection on the crankcase
(arrows).
1
296RA044 TG
296RA042 TG
: Remove the gasket (1).
296RA046 TG
296RA041 TG
296RA043 TG
1
1
While sliding the cylinder over the
piston, hold the clamping strap
tightly around the piston so that the
rings do not project – they might
otherwise break.
: Slide the cylinder over the piston,
the clamping strap moves
downwards at the same time.
Apply the clamping strap (1) so that
the piston rings do not project
beyond the cylinder wall.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
23
296RA047 TG
2
: Remove the clamping strap (1)
and wooden assembly block (2).
Crankshaft
5.6.1
Removing and Installing
– Remove the engine, b 5.4
The puller is not necessary for
removal of the crankshaft.
296RA051 TG
1
5.6
– Remove the flywheel, b 6.5
– Remove the cylinder, b 5.5
: Release the crankshaft from the
bearing seats (arrows) and take it
out of the crankcase.
– Remove the piston, b 5.8
Make sure the cylinder gasket is
properly seated.
– Push the cylinder fully home.
: Take out the screws (arrows).
296RA052 TG
296RA049 TG
296RA048 TG
1
: Pull the oil seals (arrows) off the
crankshaft stubs.
– Remove the spiral housing (1).
– Check the crankshaft and ball
bearings and replace if
necessary, b 5.6.1
: Insert the screws (arrows) to hold
the cylinder and gasket in
position..
– Tighten down the screws in an
alternate pattern.
1
296RA050 TG
– Tightening torques, b 3.4
– Remove the puller.
– Install the spacer flange, b 10.7
– Install the muffler, b 5.1
– Install the ignition module,
b 6.1.1
: Loosen the engine pan (1) at the
lug (arrow).
– Remove the engine pan.
– Reassemble all other parts in the
reverse sequence.
24
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
296RA057 TG
296RA055 TG
296RA053 TG
– Inspect the crankcase and
sealing faces (arrows) for the
engine pan and cylinder, clean
and remove gasket residue if
necessary, b 13
1
: Fit the installing sleeve (1) 4119
893 4600.
: Apply thin coating of sealant to
outside diameter (arrows) of the
oil seals, b 13
: Push the new oil seals, open side
facing the ball bearings, on to the
crankshaft stubs.
The sealing faces must be in perfect
condition.
Always replace components with
damaged sealing faces.
296RA058 TG
2
1
296RA54 TG
– Check the spacer flange (1) and
replace if necessary, b 10.7
In a new cylinder is installed, the
spacer flange must be transferred
from the old cylinder – always install
a new gasket, b 10.7
296RA056 TG
1
– Position the crankcase (1) so that
the bearing seats face up.
: Before fitting the crankshaft in the
crankcase, line it up so that the
straight stub (2) is at the same
side as the recesses (arrows).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
– Position the crankshaft,
connecting rod first, in the
crankcase.
: Place the crankshaft with
bearings and oil seals in the
bearing seats, making sure the oil
seals are firmly against their
stops (arrows) in the crankcase.
25
2
1
– Inspect and clean the sealing
faces on the engine pan and
remove any gasket residue,
b 13
: Insert the cylinder base screws in
the holes (arrows) to hold the
engine pan in position.
The sealing faces must be in perfect
condition. Always replace
components with damaged sealing
faces.
Make sure the sealant does not
project into the crankcase.
2
296RA033 TG
: Apply sealant to the groove in the
sealing face, b 13
1
3
296RA062 TG
296RA061 TG
296RA059 TG
3
: Apply the puller (1)
5910 890 4400 with the jaws
under the crankcase ribs
(arrows) and line up the spindle
(2) so that the bushing (3) is
centered on the engine pan.
: Turn the spindle clockwise until
the puller sits tightly.
Do not overtighten the spindle
because the jaws may slip off or
damage the crankcase ribs.
– Install the cylinder, b 5.5
– Prepare the puller (1)
5910 890 4400.
1
296RA060 TG
2
: Fit the No. 2 jaws (2) 0000 893
3700.
: Screw the bushing (3) 1108 893
4500 onto the puller's spindle.
Take care not to damage the
crankshaft stub.
– Line up the engine pan so that
the lug (2) is on the same side as
the crankcase contour (arrow).
: Place the engine pan (1) on the
sealing face.
Press the engine pan carefully into
position so that the sealant is evenly
distributed.
26
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
5.7
1
Bearings / Crankshaft
2
– Remove the crankshaft, b 5.4
– Pull off the oil seals, b 5.6.1
296RA066 TG
296RA063 TG
1
: Position the spiral housing (1)
over the tapered crankshaft stub
and line up the holes (arrows).
296RA064 TG
1
– Insert screws and tighten them
down firmly.
– Remove the puller.
: Pull the ball bearing (1) off the
tapered crankshaft stub.
When fitting a replacement
crankshaft, always install new ball
bearings and oil seals.
– Before installing, clean the
crankshaft, b 13
– Clean the crankshaft stubs,
b 13
– Install the cylinder, b 5.5
1
– Install the engine, b 5.4
1
2
296RA065 TG
– Reassemble all other parts in the
reverse sequence.
296RA067 TG
– Tightening torques, b 3.4
: The crankshaft (1), connecting
rod (2) and needle bearing form
an inseparable unit. It must
always be replaced as a
complete unit.
: Pull the ball bearing (1) off the
straight crankshaft stub.
Use a firm base (2) to protect the
crankshaft.
: Apply a suitable sleeve (1) to the
inner race of the ball bearing at
the fan side and press it home as
far as stop.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
27
If the piston pin is stuck, release it
by tapping the end of the drift lightly
with a hammer.
Hold the piston steady during this
process to ensure that no jolts are
transmitted to the connecting rod.
1
: Apply a suitable sleeve (1) to the
inner race of the ball bearing at
the ignition side and press it
home as far as stop.
1
: Use a suitable tool to grip the
hookless snap ring at the recess
(arrow) and ease it out.
296RA072 TG
Use a firm base (2) to protect the
crankshaft.
296RA069 TG
296RA068 TG
2
1
: Remove the piston (1) from the
connecting rod.
– Install the piston, b 5.8
– Inspect the piston and replace it if
necessary
296RA070 TG
– Lubricate the needle bearing with
oil.
– Fit new oil seals and install the
crankshaft, b 5.6.1
– Install the engine, b 5.4
– Tightening torques, b 3.4
– Inspect the piston rings and
replace if necessary, b 5.8.1
: Apply assembly drift (1)
1130 893 4700, small diameter
first, to the ignition side of the
piston.
– Reassemble all other parts in the
reverse sequence.
Piston
– Remove the engine, b 5.4
– Remove the cylinder, b 5.5
The piston has only one snap ring. It
is fitted at the fan side (straight
crankshaft stub).
28
1
296RA071 TG
5.8
: Use the assembly drift (2)
1110 893 4700 to push the piston
pin (1) out of the piston.
1
296RA073 TG
2
: Pull out the needle cage (1),
check it and replace if necessary,
b 13
– Lubricate the needle cage with oil
and push it into the connecting
rod.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
1
2
3
2
1
2
: Line up the piston as shown so
that the arrow (arrow) on the
piston crown faces the crankcase
rib (1) and the straight crankshaft
stub (2) is on the right.
: Fit the piston pin (2) on the
assembly drift (1) and slide it into
the piston.
296RA078 TG
296RA074 TG
296RA076 TG
1
: Push the large slotted diameter of
the sleeve over the magnet and
snap ring.
The inner pin (2) must point towards
the flat face (3) of the tool's shank.
: Place the piston on the
connecting rod.
: Push the assembly drift (1)
1130 893 4700, small diameter
first, through the piston and small
end (needle cage).
296RA79 TG
1
: Remove the sleeve (1)
5910 893 1708 from the installing
tool (2) 5910 890 2208.
The previous sleeve (1)
5910 893 1703 may also be used.
The new sleeve (1) 5910 893 1708
has a 20° chafer for better security
in the piston bore.
2
1
: Press the installing tool
downwards into the sleeve until
the magnet butts against the end
of the guide slot.
Use a suitable base (wooden
board).
533RA128 TG
296RA075 TG
2
296RA077 TG
1
: Attach the snap ring (1) to the
magnet (2) so that the snap ring
gap is on the flat side of the tool's
shank (arrow).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
29
5.8.1
Piston Rings
– Remove the piston, b 5.8
2
– Remove the piston rings from the
piston.
: Remove the sleeve and push it
on to the other end of the shank
as far as stop.
Fit the snap ring (1) so that its gap
(arrow) points down – it must not be
near the recess (2).
The inner pin (arrow) must again
point toward the flat face.
– Check installed position of snap
ring.
296RA083 TG
533RA131 TG
296RA081 TG
1
– Install the snap ring at the fan
side of the piston.
– Inspect the piston rings and
replace if necessary, b 5.8.1
: Apply the installing tool
5910 890 2208 with the sleeve’s
taper against the piston boss,
hold the piston steady, center the
tool shank exactly and press
home until the snap ring slips into
the groove.
– Install the cylinder, b 5.5
Make sure the tool shank is held
square on the piston pin axis.
30
– Install the engine, b 5.4
– Tightening torques, b 3.4
296RA084 TG
296RA080 TG
296RA082 TG
: Use a piece of old piston ring to
scrape the grooves clean.
: Position the new piston rings in
the groove so that the radii
(arrows) at the ring gaps face
upwards.
– Reassemble all other parts in the
reverse sequence.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Ignition timing is fixed and cannot
be adjusted during repair work.
2
296RA086TG
296RA085 TG
1
: Position the piston rings so that
the radii at the ring gap meet at
the fixing pin in the piston groove
(arrows).
The electronic (breakerless) ignition
system basically consists of an
ignition module (2) and flywheel (1).
– Check correct installed position
of the piston rings (arrows).
6.1
Troubleshooting on the ignition
system should always begin at the
spark plug, b 4.3
– Remove the fan housing, b 7.2
– Remove the fan housing, b 7.2
296RA088 TG
1
2
The ignition module accommodates
all the components required to
control ignition timing. There are
two electrical connections on the
coil body:
– High voltage output (1) with
ignition lead
– Connector tag (2) for the short
circuit wire
: Pull boot (1) off the spark plug.
2
1
296RA021 TG
Exercise extreme caution when
troubleshooting and carrying out
maintenance or repair work on the
ignition system. The high voltages
which occur can cause serious or
fatal accidents.
Removing and Installing
1
296RA087 TG
Ignition System
6.1.1
Ignition Module
– Install the piston, b 5.8
6.
Since there is no mechanical wear
in these systems, ignition timing
cannot get out of adjustment during
operation.
: Disconnect the short circuit wire
(1) and ground wire (2).
Testing in the workshop is limited to
a spark test. A new ignition module
must be installed if no ignition spark
is obtained (after checking that
wiring and stop switch are in good
condition), b 6.1.1.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
31
1
1
: Take out the screw (arrow).
: Remove the insulator (1).
– Remove the connector tag (1).
– Check the insulator and replace if
necessary.
: Take out the screw (2) and
washer.
1
296RA095 TG
296RA093 TG
296RA090 TG
2
2
: Place the ignition module (1) in
position so that the ignition lead
(2) faces the muffler and insert
the screw (arrow) with washer
– do not tighten down yet.
– Check the spark plug boot and
replace if necessary, b 6.4
– Troubleshooting, b 4.3
1
296RA096 TG
2
1
296RA094 TG
296RA091 TG
1
: Remove the ignition module (1).
: Fit the connector tag (1) and
insert the screw (arrow)
– do not tighten down yet.
– Position the insulator (1) so that
the connecting bar (2) points
towards the carburetor.
296RA092 TG
1
The ignition module (1) and ignition
lead (2) form a unit.
– Check the ignition module (1) and
replace if necessary
32
1
296RA097 TG
: Attach the lugs (arrows) of the
insulator (1) to the bosses.
2
– Push the ignition module (1) back
: Slide the setting gauge (1)
1127 890 6400 between the
arms of the ignition module and
the flywheel magnet.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
1
1
N
1
2
3
165RA183 TG
2
296RA099 TG
296RA089 TG
S
– Push the ignition module (1) back
– the flywheel must turn freely.
: Connect the ground wire (1) and
short circuit wire (2).
Using the ZAT 4 ignition tester
5910 850 4503
The setting gauge is not shown in
the illustration.
– Push the boot on to the spark
plug.
– Before starting the test, install a
new spark plug in the cylinder
and tighten it down firmly.
: Hold the setting gauge and rotate
the flywheel until the magnet
poles (arrows) are next to the
ignition module.
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
6.2
: Connect spark plug boot to the
input terminal (1). Push the
tester’s output terminal (3) on to
the spark plug.
– Press the ignition module against
the setting gauge.
– Tighten down the screws firmly.
Ignition Timing
Ignition timing is fixed and cannot
be adjusted during repair work.
Since there is no mechanical wear
in these systems, ignition timing
cannot get out of adjustment during
operation.
– Tightening torques, b 3.4
– Remove the setting gauge.
– Check operation
– rotate the flywheel and make
sure it does not touch the ignition
module.
6.3
Testing the Ignition
Module
ZTo test the ignition module, use
either the ZAT 4 ignition system
tester 5910 850 4503 or the ZAT 3
ignition system tester
5910 850 4520.
High voltage – risk of electric shock.
: Crank the engine quickly with the
rewind starter and check spark in
the tester’s window (2).
The engine may start and
accelerate during the test.
If a spark is visible, the ignition
system is in order.
If no spark is visible in the
window (2), check the ignition
system with the aid of the
troubleshooting chart, b 6.7
296RA098 TG
The ignition test refers only to a
spark test, not to ignition timing.
: Fit the ground wire (wide flag
terminal) and then the short
circuit wire (narrow flag terminal)
in the guide (arrow).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
33
– Crank the engine quickly with the
rewind starter and check spark in
the tester’s window (3).
m
67 m
The engine may start and
accelerate during the test.
3
Using the ZAT 3 ignition tester
5910 850 4520
– Before starting the test, install a
new spark plug in the cylinder
and tighten it down firmly.
If no spark is visible in the
window (3), check the ignition
system with the aid of the
troubleshooting chart, b 6.7
6.4
– Use a pointed tool to pierce the
center of the new ignition lead’s
insulation, about 67 mm from the
end of the lead.
Spark Plug Boot
The ignition module (1) and ignition
lead (2) form a unit. A new ignition
module must be installed if the
ignition lead is damaged.
– Tightening torques, b 3.4
– Connect spark plug boot to the
terminal (2).
: Attach the ground terminal (1) to
the spark plug.
– Remove the fan housing, b 7.2
– Pull the boot off the spark plug.
: Use adjusting knob (3) to set the
spark gap to about 2 mm.
165RA188 TG
2
If a spark is visible, the ignition
system is in order.
296RA102 TG
296RA100 TG
1
: Pinch the hook of the leg spring
into the center of the lead (arrow).
296RA101 TG
5
3 4
While using the ZAT 3, hold it only
by the handle (4) or position it in a
safe place. Keep fingers or other
parts of your body at least 1 cm
away from the spark windown (3),
high voltage connection (2), ground
connection (5) and the ground
terminal (1).
High voltage – risk of electric shock.
34
: Use suitable pliers to pull the leg
spring out of the spark plug boot.
– Unhook the leg spring from the
ignition lead.
– Pull the boot off the ignition lead.
296RA103 TG
2
165RA185 TG
1
– Coat inside of spark plug boot
with
STIHL Press Fluid, b 13
: Hold the ignition lead and leg
spring together and push them
into the spark plug boot.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Flywheel
296RA104 TG
b
– Remove the fan housing, b 7.2
– Unscrew the spark plug.
– Reassemble all other parts in the
reverse sequence.
– Use locking strip (1) to block the
piston, b 6.5
296RA325 TG
296RA106 TG
Do not use either graphite grease or
silicone insulating paste.
The rubber lip of the spark plug boot
must completely seal the opening
(arrows) in the fan housing.
: Unscrew the flywheel nut (arrow).
If the flywheel is stuck, use a puller.
The puller 1116 893 0800 can be
modified as shown above
– this does not affect its use in other
machines.
: Turn the screw end of the puller
to depth a = 10 mm and diameter
b = 16 mm.
296RA108 TG
296RA323 TG
: Make sure the leg spring (arrow)
locates properly inside the spark
plug boot.
a
1
296RA107 TG
6.5
1
: Screw the puller (1) 5910 893
0801 clockwise on to the
crankshaft as far as stop, then
back it off a 1/4 turn.
– Tap the end of the puller a few
times to release the flywheel
– take care not to damage the
crankshaft stub or ball bearing.
– Unscrew the puller and remove
the flywheel.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
35
Before assembly, degrease the
bore in the flywheel hub and the
crankshaft stub, b 13.
Short Circuit Wire
6.6.1
Testing
– To locate the fault, test the wires
for continuity and check
insulation for damage. If the wires
are in order, check operation of
stop switch, b 6.7
– If no fault can be found, check the
ignition system with the aid of the
troubleshooting chart, b 6.7
1
– Check ground wire for continuity.
296RA111 TG
296RA109 TG
The flywheel and magnet poles
(arrows) must not be damaged or
have turned blue. Replace flywheel
if necessary.
6.6
– Reassemble in the reverse
sequence.
If the spark plug, ignition lead and
spark plug boot are in order, check
the short circuit wire and stop
switch.
– Remove the fan housing, b 7.2
: Disconnect the short circuit wire
(1).
296RA110 TG
– Connect the ohmmeter to ground
(arrow) and the short circuit wire
(1).
: Make sure the key (arrow)
engages the slot in the crankshaft
stub.
– Check the air gap between the
ignition module and flywheel and
adjust if necessary, b 6.1.1
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
36
– Set the stop switch to "0" and
hold it in that position.
The resistance measured must be
about 0 Ω. If it is much higher, the
reason may be the stop switch or
the wire. Damaged parts must be
replaced, b 6.6.4, b 6.6.2.
– Set the stop switch to "I".
The resistance measured must be
infinitely high. If not, fit a new short
circuit wire or stop switch, b 6.6.2,
b 6.6.4.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
6.6.2
Removing and Installing
Models
SH 56, 56 C, BG 56, 56 C, 66
Separate short circuit and ground
wires are installed in these
machines and may be replaced
individually in case of damage.
2
When cleaning the machine, make
sure wires are not accidentally
disconnected.
: Disconnect the short circuit wire
(1) and ground wire (2).
– Pull the short circuit and ground
wires out of the guide (arrow).
The short circuit and ground wires
are non-interchangeable, i.e. the
short circuit wire is equipped with
narrow flag terminals (one is
insulated) and the ground wire has
wide flag terminals (with additional
wire at one end).
1
– Check the individual parts and
replace if necessary.
A faulty ground wire may impair or
prevent operation of the short circuit
wire. The ground wire must
therefore be tested for good contact
and continuity.
1
296RA114 TG
2
296RA088 TG
: Pull boot (1) off the spark plug.
: Disconnect the short circuit wire
(1) and ground wire (2) from the
stop switch (3).
: Pull the wires out of the guides
(arrows).
Models
SH 56, 56 C, BG 56, 56 C, 66
1
2
296RA113 TG
– Remove the fan housing, b 7.2
– Remove the throttle trigger,
b 9.3, b 9.4
– Remove the wires with the stop
switch.
3
Removing (all models)
– Remove the throttle rod, b 10.6
: Pull the ground and short circuit
wires out of the guides (arrows).
296RA116 TG
Short circuit and ground wires are
combined in a wiring harness. The
complete wiring must be replaced if
either wire is damaged.
296RA112 TG
Models
SH 86, 86 C, BG 66, 86 C, 86
296RA115 TG
1
: Pull the ground wire (1) off the
pin.
: Pull out the stop switch (2).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
37
Installing
Models
SH 86, 86 C, BG 66, 86 C, 86
1
: Fit the short circuit wire (1) with
the insulated flag terminal on to
the narrow connector tag.
296RA121 TG
2
: Push the ground wire terminal (1)
on to the pin (2).
: Pull the ground wire (1) off the
pin.
: Route the ground wire (1) past
the rib (arrow).
: Pull the ground wire (1) out of the
guides (arrows).
2
: Fit the ground wire (2) with
additional wire on to the wide
connector tag.
296RA120 TG
The flag terminals must point to the
right with the switch in the position
shown (small arrow).
1
2
296RA123 TG
– Push the flag terminals firmly on
to the connector tags of the stop
switch.
296RA119 TG
1
2
296RA117 TG
1
: Push the ground wire (2) into the
guides (arrows) first, then the
short circuit wire (1).
: Pull out the stop switch (1).
1
296RA118 TG
Lay the wires next to one another
without crossing over.
2
1
296RA122 TG
: Slide the stop switch (1) into the
guides (arrows) – the flag
terminals must point inside the
housing.
: Fit the short circuit wire (1) and
ground wire (2) in the guide
(arrow).
38
296RA124 TG
– Position the stop switch (1) so
that the "0" on the switch points
in the direction of the blower tube.
: Pull the wiring harness out of the
guides (arrows).
– Remove the wiring harness with
the stop switch.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
3
: Disconnect the short circuit wire
(1) and ground wire (2) from the
stop switch (3).
– Position the stop switch (1) so
that the "0" on the switch points
towards the inside of the housing.
– Check the wiring harness and
stop switch and replace if
necessary.
: Slide the stop switch (1) into the
guides (arrows) – the flag
terminals must point in the
direction of the blower tube.
A faulty ground wire may impair or
prevent operation of the short circuit
wire. The complete wiring harness
must therefore be tested for good
contact and continuity.
2
296RA129 TG
2
1
296RA127 TG
1
296RA125 TG
2
1
– Lay the wiring harness over the
dome (2) of the spring mount.
: Push the protective tube (1) of
wiring harness into the retainers
(arrows).
1
1
296RA126 TG
2
: Push the ground wire terminal (1)
on to the pin (2).
: Push the ground wire (1) into the
guides (arrows).
296RA130 TG
296RA128 TG
Installing
: Push the wiring harness, ground
wire first, into the guides
(arrows).
Lay the wires next to one another
without crossing over.
– Push the flag terminals firmly on
to the connector tags of the stop
switch.
: Fit the ground wire (2) with
additional wire on to the wide
connector tag.
The flag terminals must point to the
left with the switch in the position
shown (small arrow).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
1
296RA122 TG
: Fit the short circuit wire (1) with
the insulated flag terminal on to
the narrow connector tag.
2
: Fit the short circuit wire (1) and
ground wire (2) in the guide
(arrow).
39
All Models
6.6.3
Ground Wire
6.6.4
Stop Switch
A faulty ground wire may impair or
prevent operation of the short circuit
wire.
: Fit the ground wire (wide flag
terminal) and then the short
circuit wire (narrow flag terminal)
in the guide (arrow).
1
Separate short circuit and ground
wires are installed. The ground wire
must be replaced if it is damaged.
Models
SH 86, 86 C, BG 66, 86 C, 86
Short circuit and ground wires are
combined in a wiring harness. The
complete wiring must be replaced if
either wire is damaged.
– Check for contact and continuity
and replace wiring harness if
necessary, b 6.6.1
2
296RA099 TG
– Remove and install the wires or
wiring harness, b 6.6.2
2
296RA123 TG
296RA098 TG
Models
SH 56, 56 C, BG 56, 56 C, 66
– Remove the stop switch (1),
b 6.6.2
– Test the stop switch and replace if
necessary
– Set the stop switch to "0"
= connection
– Set the stop switch to "I"
= no connection
– Reassemble in the reverse
sequence.
: Connect the ground wire (1) and
short circuit wire (2).
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
40
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
6.7
Ignition System Troubleshooting
Engine does not run
Stop Switch:
– in position "I"?
Check the spark plug:
– Smeared with oil, black?
– Sooted?
– Electrode gap correct?
– Contacts shorted?
– Clean or replace the plug
b 6.3
Check the spark plug boot:
– Firmly seated on plug (leg spring)?
– Leg spring hook in center of ignition lead?
– Boot damaged?
– If necessary, install new spark plug boot and/
or leg spring,
b 6.4
Test ignition system:
with ZAT 3 or ZAT 4
(use ZAT 3 as main spark gap
see TI 32.94),
b 6.3
1
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
41
1
Powerful
spark?
yes
no
Air gap:
– Check ignition module/flywheel,
– reset if necessary, b 6.1.1
Check the flywheel:
– Have pole shoes turned blue?
– Install new flywheel if necessary,
b 6.5
Check ground and short circuit wires:
– Wire damaged?
– Connectors firmly seated?
– Check continuity, replace wires or wiring
harness if necessary, b 6.6.2
Check the ignition lead:
– Severe chafing?
– Spark plug boot: Holes/cracks?
– Resistance: spark plug boot to ground: spec.
1.5 – 12 kΩ
If necessary, install new spark plug boot and/or
ignition lead with module,
b 6.1.1
2
42
3
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
2
3
Check operation
of stop switch:
– Operation of stop switch:
– Position "I" = no connection
– Position "0" = connection
– Install new stop switch if necessary,
b 6.6.4
Powerful
spark?
yes
no
Install new
ignition module,
b 6.1.1
yes
Machine runs trouble-free,
no further action necessary
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Engine
runs
no
–Look for fault in fuel system or
carburetor
– Check engine for leaks
– Check position of flywheel on
crankshaft,
b 5.2, b 6.5
43
General
If the action of the starter rope
becomes very stiff and the rope
rewinds very slowly or not
completely, it can be assumed that
the starter mechanism is in order
but plugged with dirt. At very low
outside temperatures the lubricating
oil on the rewind spring may thicken
and cause the spring windings to
stick together. This has a
detrimental effect on the function of
the starter mechanism.
In such a case it is sufficient to apply
a few drops of a standard solventbased degreasant (containing no
chlorinated or halogenated
hydrocarbons) to the rewind spring.
Carefully pull out the starter rope
several times and allow it to rewind
until its normal smooth action is
restored.
7.2
Removing and Installing
1
: Take out the screws (arrows).
– Remove the fan housing (1).
The rubber lip of the spark plug boot
must completely seal the opening
(arrows) in the fan housing.
7.3
Pawls
1
1
296RA132 TG
Before installing, lubricate the
rewind spring and starter post with
STIHL special lubricant.
If clogged with dirt or pitch, the
entire starter mechanism, including
the rewind spring, must be removed
and disassembled. Take particular
care when removing the spring.
296RA325 TG
7.1
296RA134 TG
Rewind Starter
296RA131 TG
7.
– Remove the fan housing, b 7.2
: Position the fan housing (1) so
that the guide lugs (arrows)
engage the housing.
: Carefully ease the spring clip (1)
off the starter post – the rewind
spring may pop out and uncoil.
– Clean all components, b 13
Models with ErgoStart
296RA133 TG
– Relieve tension of rewind spring,
b 7.4
: Insert the screws (arrows) and
check the position of the fan
housing.
– Tightening torques, b 3.4
44
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Models with ErgoStart
1
1
– Lubricate the seats of the new
pawls, b 13
: Push the straight part of the
spring clip over the starter post
until it snaps into the groove.
1
ErgoStart
The spring may still be under
tension and must always be
relieved before assembling.
1
– Pull out the starter rope until the
engine turns – this relieves spring
tension.
296RA138 TG
: Fit the new pawls (1) in the bores
(arrows) and lubricate the pegs
on the pawls with grease, b 13
– Remove the fan housing, b 7.2
The spring clip's guide loop must be
in line with the pawl (arrow).
1
– Reassemble all other parts in the
reverse sequence.
2
296RA140 TG
Make sure washer (2) is in place.
The pawls are seated in the
ErgoStart carrier. Removal and
installation procedures are the
same as for models without
ErgoStart.
.
7.4
296RA136 TG
2
: Position the spring clip (1) so that
its loops engage the pegs on the
pawls. The rounded part of the
spring clip (arrow) must engage
the starter post’s groove.
296RA139 TG
: Pull out the pawls (1), check them
and clean or replace if necessary.
296RA137 TG
296RA135 TG
1
– Remove the spring clip and
pawls, b 7.3
: Remove the washer (1).
: Pull off the carrier (2).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
45
7.5
Rope Rotor
2
: Pull the spring (1) out of the rotor
rotor (2) and lift it away.
1
1
2
: Position the spring (1) in the rope
rotor (2) so that the spring loop
engages the lug (arrow).
2
1
296RA146 TG
2
296RA144 TG
296RA141 TG
1
Relieving tension of rewind
spring
– Remove the fan housing, b 7.2
All models
: Pull out the starter rope (1)
about 5 cm and hold the rope
rotor (2) steady.
– Inspect the spring (1), carrier (2)
and lug in the rope rotor and
replace if necessary.
296R145 TG
296RA142 TG
1
: Fit the washer (1).
– Install the pawls and spring clip,
b 7.3
1
2
– While still holding the rope rotor
steady, take three full turns off the
rope rotor.
– Reassemble all other parts in the
reverse sequence.
– Pull out the rope with the starter
grip and slowly release the rope
rotor.
The system will not be under
tension if the starter rope is broken
or the rewind spring is worn.
296RA143 TG
– Remove the spring clip and
pawls, b 7.3
– Push the spring (1) into the rope
rotor.
: Position the spring (1) in the rope
rotor (2) so that the spring loop
engages the lug (arrow).
46
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
7.6
Starter Rope / Grip
– Remove the fan housing, b 7.2
2
1
: Fit the rope rotor (2) on the starter
post so that the inner spring loop
(arrow) engages the recess (1).
Models with ErgoStart
The recess in the hub of the rope
rotor is the anchor point for the
spring.
– Remove the ErgoStart, b 7.4
Rewind spring must be relaxed.
Models with ErgoStart
– Install the ErgoStart, b 7.4
296RA148 TG
1
: Carefully remove the rope rotor
(1) – the rewind spring may pop
out and uncoil.
– Remove the starter rope, b 7.6
Models with ErgoStart
– Remove the ErgoStart, b 7.4
All models
The system will not be under
tension if the starter rope is broken.
– Remove remaining rope from the
rope rotor and starter grip.
Do not shorten the starter rope.
– Remove the rope rotor, b 7.5
All models
– Fit the washer.
– Install the pawls and spring clip,
b 7.3
– Tension the rewind spring, b 7.7
1
296R150 TG
– Remove the washer (1).
– Relieve tension of rewind spring,
b 7.5
296RA149 TG
296RA1147 TG
1
– Lubricate pegs on pawls with
grease, b 13
– Reassemble all other parts in the
reverse sequence.
– Check the rope rotor and replace
if necessary.
: Push the end of the starter rope
(1) out a little and undo the knot.
– Pull the starter rope out of the
rotor.
– Coat starter posts and bore in
rope rotor with STIHL special
lubricant, b 13
– Install the starter rope, b 7.6
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
47
Machines with
standard starter grip
Machines with
ElastoStart grip
1
165RA227 TG
296RA152 TG
165RA233 TG
1
– Pull the rope out of the starter
grip.
: Use a suitable tool to pry the cap
(1) out of the starter grip.
: Tie one of the special knots
shown in the end of the rope.
– Thread the new starter rope
through the sleeve.
– Tie a simple overhand knot in the
end of the new rope.
– Fit the washers and spring.
– Thread the rope through the top
of the starter grip.
: Pull the rope with knot into the
starter grip until it is properly
seated in the grip (small arrow).
: Pull the sleeve, washers, spring
and remaining rope (arrow) out of
the grip.
Make sure the washers and spring
remain on the sleeve while the rope
its being pulled into the grip.
1
– Pull any remaining rope out of the
sleeve. Inspect the individual
parts and replace if necessary.
165RA234 TG
296RA151 TG
165RA231 TG
: Pull the starter rope with sleeve,
spring and washers into the
starter grip (1).
Do not shorten the starter rope.
: Position cap so that its lug (1)
engages the slot in the starter
grip.
– Press the cap into the starter grip.
48
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Machines with ErgoStart
7.7
Tensioning the
Rewind Spring
The following procedure is the same
for machines with ErgoStart.
296RA153 TG
1
: Thread the rope (1) through the
hole in the rotor (arrow).
– Tie a simple overhand knot in the
end of the new rope.
1
296RA157 TG
296RA321 TG
: Thread the starter rope (1)
through the guide bushing
(arrow).
2
– Remove the fan housing, b 7.2
: Pull out a short length of starter
rope (1).
1
296R154 TG
: Use the starter rope (1) to rotate
the rope rotor (2) six turns
clockwise,
296RA156 TG
: Thread the rope (1) through the
hole in the rotor (arrow).
: Pull the rope back until the knot
locates in the recess (arrow) in
the rope rotor.
296RA155 TG
– Install the rope rotor and tension
the rewind spring, b 7.5, b 7.7
The pawls and spring clip must be
installed.
Rotating the rope and rope rotor
causes the rope to become twisted
– the rewind spring is now
tensioned.
Hold the rope rotor steady since it
will otherwise spin back and may
damage the rewind spring.
– Install the ErgoStart, b 7.4
– Install the fan housing, b 7.2
– Tie a simple overhand knot in the
end of the new rope.
: Pull rope back until knot locates
in recess (arrow) in rope rotor.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
49
7.8
2
Replacing the Rewind
Spring
– Troubleshooting, b 4.1
: Pull out the twisted rope (1) with
the starter grip and straighten it
out.
The rewind spring is correctly
tensioned when the starter grip sits
firmly in the rope guide bushing
(arrow) without drooping to one
side. If this is not the case, tension
the spring by one additional turn.
When the starter rope is fully
extended, it must still be possible to
rotate the rope rotor at least another
half turn before maximum spring
tension is reached. If this is not the
case, reduce spring tension since
there is otherwise a risk of
breakage.
296RA159 TG
1
– Hold the starter grip (1) firmly to
keep the rope tensioned.
: Let go of the rope rotor and
slowly release the starter rope so
that it can rewind properly.
To reduce spring tension:
Pull the rope out, hold the rope rotor
steady and take off one turn of the
rope.
– Install the fan housing, b 7.2
The replacement spring comes
ready for installation and is secured
in a frame.
Wear a face shield and work gloves.
– Remove the fan housing, b 7.2
– Relieve tension of rewind spring if
necessary and remove the rope
rotor, b 7.5
– Remove any remaining pieces of
old spring.
– Lubricate the spring with a few
drops of STIHL special lubricant
before installing, b 13
2
1
296RA161 TG
– Hold the rope rotor (2) steady.
296RA160 TG
296RA158 TG
1
: Line up the replacement spring
with frame – the anchor loop (2)
must be above the lug (1).
50
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
a
2
296RA12 TG
161RA212 TG
2
– Fit the rewind spring with frame in
position.
Make sure the starter post does not
touch the inner spring loop in this
process – the spring may pop out
and uncoil.
: Push the rewind spring through
the frame and into its seat in the
fan housing.
: Place anchor loop (1) in the
opening (arrow) in the installing
tool (2) 1116 893 4800
– the anchor loop must point
inwards.
Make sure the anchor loop does not
project too far. It cannot be pushed
back after it is fitted in the installing
tool
– but it can be pulled out.
1
3
296RA166 TG
1
– Push the installing tool (1) with
spring on to the starter post.
Position the installing tool (1) so that
the spring's anchor loop (2) lines up
with the lug (3).
: Use a suitable tool to engage the
anchor loop (2) on the lug (3) –
pull out the loop a little if
necessary.
Distance from end of anchor loop to
edge of spring housing
a = 20 mm.
1
161RA214 TG
296RA167 TG
1
296RA163 TG
2
Check that the rewind spring (1) is
properly seated and the anchor loop
engages the lug (arrow).
If the rewind spring has popped out,
refit it in the fan housing as follows:
– Arrange the spring in its original
position.
: Apply tool to openings (arrows) to
push the spring into its seat in the
fan housing.
: Fit the rewind spring (1) in the
installing tool (2) in the
counterclockwise direction, from
the outside inwards.
– Hold the spring windings so that
they cannot pop out.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
51
Machines with ErgoStart
Install the ErgoStart, b 7.4
2
1
– Lubricate pegs on pawls with
grease, b 13
296RA171 TG
296RA168 TG
– Install the pawls, b 7.3
– Tension the rewind spring, b 7.7
: Press the installing tool against
the spring and rotate it slightly
clockwise until the spring is
properly seated.
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
: Pull the fan housing (1) off the
handle frame (2)
– this releases the anti-vibration
springs (arrows) from their seats.
– Remove the installing tool.
8.
– Lift away the fan housing (1).
1
Repairing AV System
SH 86, 86 C, BG 66C, 86,
86 C
The handle frame and fan housing
are connected by vibration-damping
springs.
8.1
296RA172 TG
296RA163 TG
Damaged springs must always be
replaced.
Removing and Installing
Check that the rewind spring (1) is
properly seated and the anchor loop
engages the lug (arrow).
The anti-vibration springs are
installed between the handle frame
and fan housing and must be
replaced if faulty.
– Secure the spring so that it
cannot pop out.
– Remove the engine, b 5.4
– Remove the rope rotor, b 7.5
– Remove the fanwheel, b 11.2
: Unscrew the anti-vibration
springs from the bearing plugs
(arrows).
296RA170 TG
296RA173 TG
1
: Take out the screws (arrows).
52
– Apply a suitable tool to the lug
(arrow) on the bearing plug (1).
: Carefully tap the bearing plug (1)
counterclockwise to loosen it and
then unscrew.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
– Reassemble all other parts in the
reverse sequence.
1
– Tightening torques, b 3.4
Handle
SH 86, 86 C, BG 66C, 86,
86 C
: Screw the preassembled antivibration springs on to the
bearing plugs (arrow) as far as
stop.
– Check the individual parts and
replace if necessary.
– Screw the bearing lugs (1) into
the anti-vibration springs as far
as stop.
296RA179 TG
: Unscrew the bearing plugs (1)
from the anti-vibration springs.
296RA177 TG
296RA174 TG
8.2
2
: Take out the screws (arrows).
1
– Screw the bearing plugs (1)
clockwise into the bores in the fan
housing (2) as far as stop.
: Position the fan housing (1) so
that the anti-vibration springs are
in line with their seats (arrow) in
the handle frame (2).
Push the fan housing (1) with the
anti-vibration springs into the spring
seats (arrow) until they snap into
position.
: Apply a suitable tool to the lug
(arrow) on the bearing plug (1)
and rotate it clockwise until it is
firmly seated.
1
296RA180 TG
296RA175 TG
2
296RA176 TG
1
: Lift the handle (1) at the fuel tank
side and disconnect it from the
cover (arrow).
296RA170 TG
– Remove the handle (1).
: Fit the screws (arrows).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
53
1
296RA184 TG
296RA182 TG
: Pull the cover (1) off the antivibration spring.
2
: Push the pegs (arrows) to one
side and remove the handle
molding (1) from the handle (2).
1
296RA187 TG
2
1
: Push the preassembled handle
(1) on to the boss (arrow) and
anti-vibration spring (2).
If a new handle is fitted, the handle
moldings must also be replaced.
1
: Push the pegs of the new handle
molding (1) into the openings
(arrows) until they snap into
position.
296RA188 TG
– Check the handle and replace if
necessary
296RA185 TG
296RA182 TG
– Press the left side of the handle
firmly on to the anti-vibration
spring until it snaps into position.
: Insert screws (arrows) and
tighten them down firmly.
1
296RA186 TG
1
296RA183 TG
– Tightening torques, b 3.4
– Inspect the handle moldings.
– Preassemble the handle
Only remove the handle moldings if
they have to be replaced.
: Engage retaining lug of cover (1)
in the opening (arrow).
– Use a suitable tool to pry the
handle molding (1) off the handle.
54
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
9.
Control Levers
9.1
Switch Positions
On handle of models SH 56, 56 C,
BG 56, 56 C, 66
On these machines the operating
modes are set on the handle and
the carburetor.
The operating modes are selected
with the stop switch.
Setting Lever
SH 86, 86 C, BG 66C, 86,
86 C
There is no setting lever on models
SH 56, 56 C, BG 56, 56 C, 66 since
they are controlled by means of the
stop switch.
– Position F = normal run position
– engine runs or may start in this
position
– Position0 = engine off
– ignition is switched off
(not locked)
– Position I = normal run position
– engine runs or may start in this
position
296RA192 TG
296RA189 TG
296RA190 TG
On handle of models SH 86, 86 C,
BG 66C, 86, 86 C
9.2
1
– Remove the handle molding,
b 9.4
– Position0 = engine off
– ignition is switched off
(not locked)
: Squeeze the lugs (arrows)
together and push out the setting
lever (1).
On carburetor of all models
– Inspect the setting lever and
handle molding and replace if
necessary
– Setting lever in position (arrow)
= full throttle
– engine is kept in full throttle
position
296RA191 TG
2
– Position F = normal run position
– Position k = warm start
– warm engine is started in this
position
– Position d = cold start
– cold engine is started in this
position
1
296RA193 TG
The rotary knob returns to the run
position when the throttle trigger is
operated.
– Line up the setting lever (1) so
that it engages the stop (2).
: Push the lugs of the setting lever
(1) into the hole (arrow) until it
snaps into position.
– Fit the handle molding, b 9.4
– Check operation.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
55
9.3
Throttle Trigger
SH 56, 56 C, BG 56, 56 C,
66
2
2
1
1
– Remove the fan housing, b 7.2
– Pull the boot off the spark plug.
296RA196 TG
296RA178 TG
296RA194 TG
1
– Check seat of pivot pin (1). If it is
damaged, install a new fan
housing, b 11.3
: Position the handle molding (1)
and push it on to the pivot pin (2),
making sure the recess (arrows)
engages the stop switch.
– Line up the throttle trigger (2) –
the arm (arrow) must point in the
direction of the throttle rod.
: Push the throttle trigger (2) on to
the pivot pin (1).
: Take out the screws (arrows).
296RA199 TG
– Remove the handle molding (1).
2
1
: Disconnect the throttle rod (1)
from the trigger (arrow).
– Pull off the throttle trigger (2),
check it and replace if necessary.
56
1
296RA197 TG
296RA195 TG
: Fit the screws (arrows).
– Attach the throttle rod (1) to the
trigger (arrow).
– Check that handle molding is
properly seated.
– Insert screws and tighten them
down firmly.
– Tightening torques, b 3.4
– Check operation.
– Reassemble all other parts in the
reverse sequence.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Throttle Trigger
SH 86, 86 C, BG 66C, 86,
86 C
1
296RA200 TG
296RA202 TG
2
296RA205 TG
1
1
– Remove the fan housing, b 7.2
: Ease the detent spring slightly
apart and lift it out over the guides
(arrows)
– do not overstretch the detent
spring.
1
– Check the cam (2) and detent
spring (1) and replace if
necessary
– Pull the boot off the spark plug.
: Take out the screws (arrows).
– Carefully remove the handle
molding (1).
: Ease the lugs (arrows) slightly
apart and push the outer handle
molding (1) off the handle frame.
296RA206 TG
1
The cam may fall out.
296RA203 TG
2
1
296RA201 TG
3
: Position the handle molding (1)
with the peg (arrow) against the
handle frame.
: Push the detent spring (1) into
the guides (arrows) so that it
snaps into position
– do not overstretch the detent
spring.
: Disconnect the throttle rod (1)
from the trigger (arrow).
1
1
– Pull off the throttle trigger (2) and
cam (3).
296RA207 TG
9.4
: Push lugs of handle moldings into
the recesses (arrows) until they
snap into position.
296RA204 TG
– Check the individual parts and
replace if necessary.
: Ease the lugs (arrows) slightly
apart and push the inner handle
molding (1) off the handle frame.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
57
1
– Position the cam so that the
square seat (1) faces away from
the handle frame.
: Carefully attach the throttle rod
(1) to the trigger (arrow).
: Fit the screws (arrows).
– Check that handle molding is
properly seated.
The cam may fall out.
– Position the throttle trigger so that
the arm (2) faces in the direction
of the throttle rod.
– Insert screws and tighten them
down firmly.
1
: Push the cam and throttle trigger
on to the pivot pins (arrows).
– Check operation.
– Reassemble all other parts in the
reverse sequence.
2
296RA211 TG
If a pivot pin is broken, install a new
handle housing.
1
296RA212 TG
2
296RA210 TG
296RA208 TG
1
– Tightening torques, b 3.4
296RA209 TG
: Position the handle molding (1)
so that the setting lever (2) pivot
engages the cam seat (arrow).
The lug (1) must engage the cam's
guide (arrow).
58
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.
Fuel System
When working on fuel system
hoses:
1
To avoid damaging hoses, do not
use pliers or other sharp-edged
tools.
2
Air Filter
Dirty air filters reduce engine power,
increase fuel consumption and
emissions, and make starting more
difficult.
296RA214 TG
Use STIHL Press Fluid when fitting
hoses, b 13
: Pull off the retainer (1).
3
296RA216 TG
2
Disconnect and connect hoses by
hand, i.e. without tools.
10.1
1
– Fit the filter (1) in the filter
housing.
– Take the filter (2) out of the
housing and check it
– see instruction manual.
– Line up the retainer (2) – the tab
(3) must point down.
: Push the retainer (2) into its seat
(arrow).
The air filter should be checked
when there is a noticeable loss of
engine power.
1
1
296RA217 TG
296RA215 TG
– See also Troubleshooting, b 4.4
: Squeeze the tabs (arrows)
together and push the twist lock
out of the filter cover.
296RA213 TG
– Fit the filter cover (1).
: Open the twist lock (arrow).
– Check the individual parts and
replace if necessary.
: Close the twist lock (arrow).
– Reassemble in the reverse
sequence.
– Remove the filter cover (1).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
59
10.2
Baffle / Filter Housing
2
1
296RA220 TG
296RA218 TG
1
: Remove the gasket (1).
296RA223 TG
1
– Position the filter housing (1) so
that the tab (2) is at the top.
– Remove the fan housing, b 7.2
– Slide the filter housing (1) over
the studs.
– Remove the air filter, b 10.1
: Fit the nuts (arrows) and tighten
them down firmly.
296RA221 TG
: Pull out the baffle (1), check it
and replace if necessary.
1
2
296RA224 TG
296RA219 TG
: Check and clean the sealing
faces (arrows) on the carburetor
and filter housing, b 13
1
Always replace components with
damaged sealing faces.
: Use screwdriver 5910 890 2420
to unscrew the nuts (arrows).
– Position the baffle (1) so that the
recess (2) is at the top.
– Remove the filter housing (1).
: Push the baffle (1) on to the
intake (2).
1
– Reassemble all other parts in the
reverse sequence.
296RA222 TG
– Inspect the filter housing and
baffle and replace if necessary.
– Tightening torques, b 3.4
: Fit the gasket (1).
60
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.3
Removing and Installing
the Carburetor
– Remove the fan housing, b 7.2
1
296RA227 TG
– Open the fuel tank cap and drain
the fuel tank, b 1
: Remove the gasket (1).
Disconnect the fuel hoses only
when the tank cap is open.
1
296RA031 TG
2
– Remove the filter housing,
b 10.2
– Push the carburetor into position.
: Push the new fuel hose (1) and
fuel return hose (2) on to the
stubs on the connector (small
arrow).
Always install new fuel hoses.
– Remove the throttle rod, b 10.6
1
296RA022 TG
2
296RA324 TG
Take care not to damage the new
fuel hoses.
: Disconnect the fuel hose (1) and
fuel return hose (2) from the
stubs (arrows).
: Check and clean the sealing
faces (arrows) on the spacer
flange and carburetor, b 13
– Install the throttle rod, b 10.6
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
Always replace components with
damaged sealing faces.
1
296RA229 TG
296RA226 TG
1
: Fit the gasket (1).
: Remove the carburetor (1).
– Check the carburetor and service
or replace if necessary.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
61
10.3.1 Leakage test
10.4
2
10.4.1 Metering Diaphragm /
Manual Fuel Pump
Install new fuel hoses after
completing the test.
1
– Remove the carburetor, b 10.3
1
: Push the ring (1) to the right and
pump air into the carburetor until
the pressure gauge (2) indicates
a pressure of about 0.8 bar
(80 kPa).
296RA230 TG
– Push the pressure hose of pump
0000 850 1300 on to the nipple.
Take care not to damage the new
fuel hoses.
– Remove the carburetor, b 10.3
: Take out the screws (arrows).
If this pressure remains constant,
the carburetor is airtight. However, if
it drops, there are three possible
causes:
: Push the pressure hose (1)
1110 141 8600 on to the
nipple (2) 0000 855 9200.
1. The inlet needle is not sealing
(foreign matter in valve seat,
sealing cone of inlet needle
is damaged or
inlet control lever is sticking).
Remove to clean,
b 10.4.2
2. Metering diaphragm or gasket
damaged, replace if necessary,
b 10.4.1
1
296RA231 TG
165RA336 TG
2
296RA028 TG
In the case of problems with the
carburetor or fuel supply system,
also check and clean or replace the
tank vent, b 10.8
The carburetor can be tested for
leaks with the pump 0000 850 1300.
Servicing the Carburetor
: Remove the complete flange (1).
: Push the pressure hose with
nipple on to the carburetor’s fuel
stub (arrow).
– After completing the test, push
the ring (1) to the left to vent the
system and then pull the fuel
hose off the carburetor.
– Install the carburetor, b 10.3
– Reassemble all other parts in the
reverse sequence.
1
296RA232 TG
296RA178 TG
3. Pump diaphragm or
gasket damaged, replaced
if necessary, b 10.4.3
: Remove the metering diaphragm
and gasket (1).
– Tightening torques, b 3.4
62
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
2
1
1
: Carefully separate the metering
diaphragm (2) and gasket (1).
The diaphragm material is
subjected to continuous alternating
stresses and eventually shows
signs of fatigue, i.e. the diaphragm
distorts and swells and has to be
replaced.
: Check the cap and replace it if
necessary.
296RA238 TG
296RA315 TG
296RA233 TG
1
– Place the flange in position
– stub (1) must be on same side
as throttle shutter.
: Insert two screws (arrows) to hold
the flange, gasket and diaphragm
in position.
2
1
296RA236 TG
– Check the metering diaphragm
for signs of damage and wear
and replace if necessary.
– Install a new gasket.
296RA239 TG
: Line up the gasket (1) and
metering diaphragm (2) with the
holes (arrows).
– Insert the other screws.
1
296RA237 TG
296RA234 TG
1
: Remove the flange (1).
: Insert the screws (arrows) and
tighten them down firmly in an
alternate pattern.
– Reassemble all other parts in the
reverse sequence.
– Check operation.
: Position the cap (1) in the annular
groove (arrow).
– Fit the end cover.
296RA235 TG
1
: Remove the cap (1).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
63
10.4.2 Inlet Needle
– Remove the spring (2). Inspect
and replace if necessary.
Make sure the spring locates on the
control lever’s nipple.
– Press the inlet control lever down
and secure it with the screw.
– Check that inlet control lever
moves freely.
– Remove the metering
diaphragm,
b 10.4.1
533RA309 TG
296RA240 TG
– Install the metering diaphragm,
b 10.4.1
: If there is an annular indentation
(arrow) on the sealing cone of the
inlet needle, fit a new inlet
needle.
: Take out the screw (arrow).
– Reassemble all other parts in the
reverse sequence.
10.4.3 Pump Diaphragm
2
296RA245 TG
1
2
: Pull the inlet control lever (1) with
spindle (2) out of the inlet
needle’s groove.
296RA243 TG
296RA241 TG
1
– Remove the carburetor, b 10.3
: Take out the screw (arrow).
: Fit the inlet needle (1).
: Fit the spring (2) in the bore.
The small spring under the inlet
control lever may pop out.
1
296RA242 TG
2
: Remove the inlet needle (1).
64
1
296RA244 TG
1
296RA246 TG
2
: Carefully remove the end cover
(1).
: Position the inlet control lever (1)
with spindle (2) on the spring’s
seat (arrow) first, then slide the
inlet control lever’s clevis into the
groove in the inlet needle.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
1
296RA249 TG
: Carefully remove the gasket with
pump diaphragm from the end
cover.
: Use a needle to remove the fuel
strainer (1) from the carburetor
body.
– Reassemble in the reverse
sequence.
1
2
– Check fuel strainer for
contamination and damage.
Clean or replace if necessary.
1
: Fit the gasket (1) so that the
contours (arrows) match and it is
held in position by the pegs (2).
296RA253 TG
– Check the pump diaphragm for
signs of damage and wear. Install
a new gasket.
– Align the end cover (1) so that its
pegs engage the holes in the
carburetor body.
296RA250 TG
2
: Carefully separate the pump
diaphragm (1) and gasket (2).
The diaphragm material is
subjected to continuous alternating
stresses and eventually shows
signs of fatigue, i.e. the diaphragm
distorts and swells and has to be
replaced.
– Position the end cover (1) so that
the idle speed screw (arrow) is at
the same side as the adjusting
screws.
: Turn lever (2) on throttle shaft a
little and place the end cover (1)
against the carburetor body from
below so that the gasket and
pump diaphragm remain in
position on the end cover.
2
1
2
– Check that diaphragm and
gasket are properly seated.
296RA251 TG
2
296RA248 TG
1
1
296RA252 TG
296RA247 TG
2
: Tighten down the screw (1) firmly.
– Reassemble all other parts in the
reverse sequence.
: Fit the diaphragm on the gasket
(1) so that the contours (arrows)
match and it is held in position by
the pegs (2).
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
65
10.4.4 Throttle Lever /
Rotary Knob
1
– Remove the carburetor, b 10.3
1
296RA254 TG
1
– Push the throttle lever (1) on to
the end of the throttle shaft
(arrow).
– Position the rotary knob (1) so
that the flat in the knob's bore and
lines up with the flat side (arrow)
of the choke shaft.
: Tighten down the screw (2) firmly.
: Push the rotary knob (1) on to the
choke shaft until it snaps into
position.
: Take out the screw (arrow).
– Pull off the throttle lever (1).
– Reassemble all other parts in the
reverse sequence.
296RA257 TG
1
2
296RA255 TG
1
296RA259 TG
296RA256 TG
2
Make sure the spacer sleeve (1) is
in place.
– Check operation.
: Rotate the choke shaft. The
choke lever (1) must engage the
throttle lever (arrow).
: Position the throttle lever (2) so
that the arm with the bore (arrow)
faces up.
296RA258 TG
1
: Pull off the rotary knob (1).
66
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.4.5 Adjusting Screws
Low speed screw
– Screw down the low speed screw
(L) as far as stop.
1
High speed screw
296RA261 TG
There are three adjusting screws on
the carburetor:
H = high speed screw (1)
L = low speed screw (2)
LA = idle speed screw (3)
: Use special tool 5910 890 4501
to pry the limiter cap (1) off the
low speed screw.
Do not re-install used cap – always
fit a new cap.
If the carburetor cannot be adjusted
properly, the problem may be the
adjusting screws.
: Use special tool 5910 890 4501
to pry the limiter cap (1) off the
high speed screw.
1
The high speed screw H and low
speed screw L each have a limiter
cap, which has to be removed
before the screw is removed.
Do not re-install used cap – always
fit a new cap.
296RA262 TG
Always install new limiter caps.
– Remove the fan housing, b 7.2
1
: Take out the low speed screw (1).
296RA266 TG
It is not necessary to remove the
carburetor to remove and install the
adjusting screws. For the sake of
clarity, however, the illustrations
show the carburetor removed from
the machine.
1
296RA265 TG
3
1
296RA260 TG
2
– Continue with high speed screw.
: Take out the high speed screw
(1).
296RA263 TG
– See also carburetor
troubleshooting, b 4.4
: Inspect the tip (arrow) for
damage or wear and replace the
screw (L) if necessary.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
67
1
1
0
2
14
4
12
6
Always use a new limiter cap and
position it so that the long part of the
cap butts against the underside of
the stop (arrow). Only then may it be
pushed on to the high speed screw.
: Push the limiter cap (1) on to the
low speed screw as far as the first
detent – the limiter cap is thus
prepared for final installation.
Pre-installing limiter caps
296RA264 TG
Always use a new limiter cap and
position it so that the long part of the
cap butts against the underside of
the stop (arrow). Only then may it be
pushed on to the low speed screw.
: Push the limiter cap (1) on to the
low speed screw as far as the first
detent – the limiter cap is thus
prepared for final installation.
68
High speed and low speed screws
can now be adjusted through the
pre-installed limiter caps.
Starting with the low speed and high
speed screws against their seats,
turn them counterclockwise.
: Turn the high speed screw H (1)
one full turn Turn the low speed
screw L (2) one full turn
– Carry out basic setting, b 10.5.1
This completes the basic setting of
the high speed screw (H) and the
low speed screw (L).
10.5
– Remove the blower tube or
catcher bag.
1
Low speed screw (L)
296RA269 TG
296RA267 TG
296RA268 TG
10
– Screw down the high speed
screw (H) as far as stop.
High speed screw (H)
8
: Inspect the tip (arrow) for
damage or wear and replace the
high speed screw if necessary.
2
Adjusting the Carburetor
10.5.1 Basic Setting
The basic setting is necessary only
if the high speed screw (H) or low
speed screw (L) has to be replaced,
the limiter caps have been removed
or after cleaning and adjusting the
carburetor from scratch.
– Pre-install the new limiter caps on
the high speed and low speed
screws, b 10.4.5
The air filter must be installed.
– Allow engine to warm up.
Setting disk 5910 893 6600 may be
fitted on the screwdriver
5910 890 2305 to simplify
adjustments.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
1
a
10.5.2 Standard Setting
1
2
12
6
14
4
0
8
: Push screwdriver (1)
5910 890 2305 into the adjusting
screws (arrow).
– After completing the basic settng,
push the limiter caps fully on to
the adjusting screws.
Adjust idle speed with a tachometer.
Adjust specified engine speeds
within tolerance of ± 200 rpm.
: Do not push the limiter caps up
against the carburetor body since
they will otherwise be damaged.
Clearance 'a' (arrow) must be at
least 1 mm.
1. Adjust engine speed
idle speed screw (LA)
to 3,600 rpm.
2. Turn the low speed screw (L)
clockwise or counterclockwise
to obtain the maximum engine
speed.
If this speed is higher than
4,000 rpm, abort the procedure and
start again with step 1.
3. Use the idle speed screw (LA)
to set the engine speed again to
3,600 rpm.
296RA272 TG
296RA271 TG
296RA270 TG
10
1
The limiter caps must not be
removed for the standard setting.
Always perform the following steps
before carrying out any
adjustments:
– Troubleshooting, b 4.4
The range of adjustment of the high
speed screw (H) and low speed
screw (L) is now limited..
Perform standard setting by turning
the high speed screw (H)
counterclockwise and the low speed
screw (L) clockwise until they are
just against their stops.
The basic setting of the high speed
screw (H) and low speed screw (L)
is now fixed.
4. Set the engine speed to
2,800 rpm with the low speed
screw (L)
5. Set engine's maximum speed
to 14,000 rpm with the high speed
screw (H)
.
– Remove the blower tube or
catcher bag.
– Inspect the spark arresting
screen (if fitted) and clean or
replace if necessary. b 5.1
– Check the air filter and clean or
replace if necessary, b 10.1
Standard Setting
– Shut down the engine.
– Turn the high speed screw (H)
slowly counterclockwise as far as
stop, but not more than a
3/4 turn.
– Turn the low speed screw (L)
slowly clockwise as far as stop,
but not more than a
3/4 turn.
– Check engine running behavior
– the engine must accelerate and
idle smoothly.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
69
– Carry out standard setting.
– Allow engine to warm up.
– Turn the idle speed screw (LA)
clockwise as far as the stop, then
back it off 3 full turns.
Erratic idling behavior, poor
acceleration
(although standard setting is
correct)
Turn the adjusting screws only very
slightly. Even minor adjustments
can noticeably affect engine running
behavior.
If the setting is made too lean there
is a risk of engine damage as a
result of lack of lubrication and
overheating.
If the adjustments produce no
improvement, see the
troubleshooting charts for the
ignition system, b 4.3, carburetor
and engine, b 4.4, b 4.5.
Idle setting too lean.
– Allow engine to warm up.
10.6
– Check standard setting.
2
– Attach the throttle rod (1) to the
lever (arrow) on the carburetor.
296RA319 TG
It is usually necessary to change the
setting of the idle speed screw (LA)
after every correction to the low
speed screw (L).
– Remove the fan housing, b 7.2
296RA318 TG
A minor correction may be
necessary if engine power is not
satisfactory when operating at high
altitude.
1
: Position the throttle rod (1) so
that the bend (2) points towards
the carburetor.
Throttle Rod
– Turn the low speed screw (L)
counterclockwise
(max. 3/4 turn)until the engine
runs and accelerates smoothly.
Adjustment for operation at high
altitude
– Check the throttle rod and
replace if necessary
296RA317 TG
Adjusting engine idle speed
– Remove the handle molding,
b 9.3, b 9.4
: Disconnect the throttle rod from
the trigger (arrow).
– Attach the throttle rod to the
trigger (arrow).
– Fit the handle molding, b 9.3,
b 9.4
– Allow engine to warm up.
1
– Check operation.
– Turn the high speed screw (H)
clockwise (leaner) – no further
than stop.
296RA316 TG
– Reassemble all other parts in the
reverse sequence.
: Disconnect the throttle rod (1)
from the lever (arrow) on the
carburetor.
70
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.7
Removing and Installing
the Spacer Flange
1
A damaged spacer flange can result
in engine running problems.
1
– Remove the carburetor, b 10.3
– Inspect the spacer flange (1) and
replace it if necessary – even
very minor damage can result in
engine running problems, b 4.5
296RA274 TG
296RA225 TG
– Troubleshooting, b 4.5
: Position the spacer flange (1)
with gasket against the cylinder
intake port so the guides engage
the openings (arrows).
296RA040 TG
1
1
296R228 TG
– Remove the spacer flange (1).
296RA275 TG
: Take out the screws (arrows).
: Check and clean the sealing
faces (arrows) on the cylinder
and spacer flange, b 13
296RA041 TG
1
: Fit the screws (arrows).
– Check that gasket is properly
seated.
The sealing faces must be in perfect
condition.
Always replace components with
damaged sealing faces.
– Insert screws and tighten them
down firmly.
– Reassemble all other parts in the
reverse sequence.
: Remove the gasket (1).
1
296R273 TG
– Tightening torques, b 3.4
: Fit the new gasket (1) over the
guides (arrows) on the spacer
flange.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
71
10.8
Tank Vent
10.8.1 Testing
– Open the fuel tank cap and drain
the fuel tank, b 1
2
: Push the nipple (1)
0000 855 9200 into the fuel hose
(arrow).
– Close the tank cap.
– Remove the carburetor, b 10.3
296RA278 TG
2
296RA276 TG
1
– Disconnect the fuel hoses from
the carburetor and push them on
to the stubs on the connector.
: Seal one fuel hose (arrow) with a
plug.
Vacuum test
: Push the ring (1) to the left and
connect the pump (2)
0000 850 1300 to the nipple
(arrow)
– subject the fuel tank to a
vacuum.
Equalization of pressure takes
place via the tank vent. There must
be no buildup of vacuum in the tank.
1
296RA279 TG
1
296RA277 TG
If problems occur on the carburetor
or the fuel supply system, also
check and clean the tank vent and
replace it if necessary. Check
function by performing pressure and
vacuum tests on the tank via the fuel
hose.
Pressure test
: Push the ring (1) to the right and
connect the pump (2)
0000 850 1300 to the nipple
(arrow)
– pressurize the fuel tank.
– Operate the pump until the
pressure gauge indicates a
pressure of 0.5 bar. If this
pressure remains constant for at
least 20 seconds, the tank,
including the tank vent, is airtight.
If the pressure drops, the leak
must be located and the faulty
part replaced.
Install new fuel hoses after
completing the test.
Take care not to damage the new
fuel hoses.
– Reassemble in the reverse
sequence.
– Clean the area around the tank
vent.
– If necessary, install a new tank
vent or tank, b 10.8
72
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
296RA280 TG
1
10.9
Fuel Intake
10.9.1 Pickup Body
– Remove the fan housing, b 7.2
In the event of problems with the
fuel supply system, always check
the fuel tank and the pickup body
first.
– Remove the air filter, b 10.1
– Troubleshooting, b 4.4
: Pry the tank vent (1) out of its
seat using the rib (arrow) for
leverage.
Do not use pliers or other pointed or
sharp-edged tools.
Clean the fuel tank if necessary,
Always install a new tank vent.
1
Any impurities mixed with the fuel
are retained by the pickup body
(filter). The fine pores of the filter
eventually become clogged with
minute particles of dirt. This restricts
the passage of fuel and results in
fuel starvation.
– Open the tank cap and drain the
tank.
296RA282 TG
10.8.2 Removing and Installing
– Open the tank cap.
: Use hook 5910 893 8800 to
remove the pickup body (1) from
the fuel tank.
Do not overstretch the fuel hose.
– Pull the pickup body (1) off the
fuel hose. Inspect it and clean or
replace if necessary.
– Reassemble in the reverse
sequence.
– Pour a small amount of clean
gasoline into the tank. Close the
tank and shake the saw
vigorously.
1
296RA281 TG
– Open the tank again and drain it.
Dispose of fuel properly in
accordance with environmental
requirements.
: Push the new tank vent (1) into
the fuel tank bore until it snaps
into position.
– Reassemble all other parts in the
reverse sequence.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
73
1
296RA283 TG
296RA285 TG
1
– Remove the fan housing, b 7.2
: Push the fuel hose (1) on to the
connector's stub as far as stop,
making sure the shoulder
(arrows) engages properly.
Before removing the fuel hoses,
check them to see if they need to be
replaced.
The fuel hose must be pushed fully
home.
1
Disconnect the fuel hoses only
when the tank cap is open.
– Fit the pickup body on the fuel
hose.
296RA286 TG
: Disconnect the fuel return hose
(1) from the carburetor and
connector (arrows).
: Pull the connector (1) with fuel
hose and pickup body out of the
fuel tank.
296RA284 TG
1
1
Take care not to damage the new
fuel hoses.
– Reassemble in the reverse
sequence.
74
1
2
: Pry out the grommet (1).
3
296RA287 TG
: Disconnect the fuel hose (1) from
the carburetor and connector
(arrows).
Install the new fuel hoses.
– Coat the stub with STIHL
Press Fluid, b 13
– Remove the carburetor, b 10.3
: Pry out the connector (1).
– Remove the filter housing,
b 10.2
1
296RA289 TG
Fuel Intake
296RA290 TG
10.9.2 Fuel Hoses
– Inspect the grommet and replace
if necessary
– Reassemble in the reverse
sequence.
: Pull the pickup body (1) and
connector (2) off the fuel hose
(3).
– Check the individual parts and
replace if necessary.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
10.9.3 Fuel Tank Cap
See instruction manual.
– Open the tank cap.
296RA291 TG
1
296RA293 TG
: Fit the fuel hose (1) with pickup
body through the bore (arrow) in
the fuel tank.
: Disconnect the tank cap cord
from the slot (arrow).
296RA292 TG
1
: Line up the connector (1) and
push it into the bore until the tab
engages the recess (arrow) and
locates against the housing.
– Inspect the tank cap. Install new
sealing ring or tank cap if
necessary.
– Reassemble in the reverse
sequence.
– Check for leaks.
– Coat the connector with STIHL
Press Fluid, b 13
Install the new fuel hoses.
Take care not to damage the new
fuel hoses.
– Push the fuel hoses on to the
stubs of the connector (1) and
install the carburetor, b 10.3
– Reassemble all other parts in the
reverse sequence.
– Tightening torques, b 3.4
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
75
11.
Blower and Vacuum Attachment
11.1
Intake Screen
1
1
296RA299 TG
: Ease the retaining tab (arrow) to
one side and unlock the intake
screen (1).
296RA297 TG
– Inspect the outer fan housing and
replace if necessary, b 11.2
– Apply intake screen's pivot pins
(arrows) to the tabs on the outer
fan housing and press down.
– Check the intake screen (1) and
torsion spring (2) and replace if
necessary
1
The torsion spring may pop out.
1
296RA298 TG
296RA295 TG
1
– Open the intake screen (1).
: Position legs of torsion spring (1)
in the recesses (arrows).
: Press down the tabs (arrows).
– Check installed position of intake
screen.
1
The torsion spring must be over the
lug (1) and the intake screen's pivot
pins must be behind the tabs
(arows) on the outer fan housing.
296RA296 TG
296RA288 TG
1
: Carefully pull pivot pins of intake
screen (1) out of their mounts –
the torsion spring may pop out.
– Remove the intake screen (1)
– the torsion spring may fall out.
76
: With the intake screen (1) still
depressed, push it into the
mounts to engage the pivot pins
in position.
296RA300 TG
1
296RA294 TG
2
: Position intake screen (1) and
torsion spring (arrow) against the
outer fan housing.
Spring force now holds the intake
screen against the outer fan
housing.
– Press the intake screen against
the outer fan housing until it
snaps into position.
The torsion spring may pop out.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
11.2
Fanwheel
2
1
: Take out the screws (arrows).
296RA305 TG
296RA303 TG
296RA301 TG
1
: Remove the washer (1).
: Fit the washer (arrow).
: Pull off the fanwheel (2).
– Push the fanwheel into position.
– Lift away the outer fan housing
(1).
1
296RA105 TG
– Use locking strip (1) to block the
piston, b 6.5
296RA306 TG
296RA304 TG
1
: Remove the washer (arrow).
: Fit the washer (1).
– Check the individual parts and
replace if necessary.
– Fit the nut and tighten it down
firmly.
The fanwheel must not be cracked
or damaged in any other way.
: Unscrew the nut (arrow)
– it has a left-hand thread.
1
296RA301 TG
296RA302 TG
Damage on the fanwheel can result
in consequential damage
– bearing damage due to out of
balance, or the high centrifugal
forces may cause the fanwheel to
shatter.
– Place the outer fan housing (1) in
position.
: Insert screws (arrows) and
tighten them down firmly.
– Tightening torques, b 3.4
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
77
11.3
Removing and Installing
the Fan Housing
SH 56, 56 C, BG 56, 56 C,
66
11.3.1 Removing and Installing
the Fan Housing
SH 86, 86 C, BG 66C, 86,
86 C
2
296RA308 TG
296RA307 TG
296RA171 TG
1
– Remove the fanwheel, b 11.2
– Remove the fanwheel, b 11.2
– Remove the engine, b 5.4
– Remove the engine, b 5.4
– Remove the throttle trigger,
b 9.3
– Remove the throttle trigger,
b 9.3
: Pull the fan housing (1) off the
handle frame (2)
– this releases the anti-vibration
springs (arrows) from their seats.
– Lift away the fan housing (1).
296RA172 TG
– Remove the short circuit wire,
b 6.6.2
– Inspect the fan housing and
replace if necessary
– Reassemble in the reverse
sequence.
296RA322 TG
A replacement fan housing comes
with the pickup body and fuel hoses,
tank vent and tank cap
preassembled, i.e. these parts do
not need to be transferred from the
old housing.
: Disconnect the wiring harness
(arrows), b 6.6.2
: Inspect the fan housing and
replace if necessary
A replacement fan housing comes
with preassembled anti-vibration
springs (arrows).
– Push the anti-vibration springs
(arrows) of fan housing into their
seats in the handle housing until
they snap into position, b 8.1
– Tightening torques, b 3.4
– Reassemble all other parts in the
reverse sequence.
296RA170 TG
– Tightening torques, b 3.4
: Take out the screws (arrows).
78
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
11.3.2 Removing and Installing
the Handle Housing
SH 86, 86 C, BG 66C, 86,
86 C
11.4
Blower Tube
BG Models
1
– Remove the fan housing,
b 11.3.1
296RA310 TG
296RA309 TG
296RA311 TG
2
1
: Unlock the union nut (1) through
the opening (arrow) and turn it
counterclockwise.
: Position the blower tube (1) so
that the marks (arrows) are in
alignment.
– Push the blower tube on to the
fan housing stub.
– Pull off the blower tube (2).
– Remove the handle, b 8.2
– Check the handle housing and
replace if necessary
– Check the short circuit wire with
stop switch and replace if
necessary, b 6.6.2
– Inspect outer handle molding and
replace if necessary, b 9.4
– Reassemble in the reverse
sequence.
– Tightening torques, b 3.4
296RA312 TG
A replacement handle housing
comes with the pickup body and fuel
hoses, tank vent and tank cap
preassembled, i.e. these parts do
not need to be transferred from the
old housing.
1
296RA313 TG
1
: Turn the union nut (1) clockwise
until it snaps into position.
: Pull off the union nut (1) over the
raised moldings (arrows).
– Check the individual parts and
replace if necessary.
A relacement blower tube comes
with the union nut preassembled.
– Reassemble in the reverse
sequence.
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
79
11.5
Elbow
SH Models
1
296RA314 TG
296RA165 TG
2
The procedure for removing and
installing the elbow is the same as
for the blower tube, b 11.4.
The elbow and union nut form a
single unit and cannot be taken
apart.
11.6
– Push the suction tube (1) on to
the intake stub.
: Slide the union nut (2) into place
and turn it clockwise until the
safety lock engages, then
continue turning it until there is
noticeable resistance and it is
firmly seated.
2
Suction Tube
SH Models
1
2
296RA164 TG
296RA169 TG
1
– Unscrew the union nut (1)
counterclockwise until it is
against the safety lock.
– Open the intake screen (1),
b 11.1
: Unlock the union nut (1) through
the opening (arrow) and continue
turning it counterclockwise.
: Position the suction tube (2) so
that the marks (arrows) are in
alignment.
– Hold the intake screen steady
and pull off the suction tube (2).
80
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
12.
Special Servicing Tools
New Special Tools
No.
Part Name
Part No.
Application
1
2
3
Test flange
Puller
Sleeve
5910 850 4200
5910 893 0801
5910 893 1708
Leakage test
Releasing flywheel
Sleeve (with 20° chamfer) for
installing tool 8
Rem.
1
Existing Special Tools
No.
Part Name
Part No.
Application
1
2
Carburetor and engine tester
Sealing plate
- Hose for leakage test
- Nipple
Puller
Screwdriver
- Setting disk
0000 850 1300
0000 855 8106
1110 141 8600
0000 855 9200
5910 890 4501
5910 890 2305
5910 893 6600
5
6
Socket DIN 3124, 13 mm
Setting gauge
5910 893 5608
1127 890 6400
7
8
9
10
Ignition system tester, ZAT 4
Ignition system tester, ZAT 3
Puller
- Jaws (No. 3.1)
- Jaws (No. 2)
Threaded bushing
5910 850 4503
5910 850 4520
5910 890 4400
0000 893 3706
0000 893 3706
1108 893 4500
11
12
13
14
15
16
17
18
19
Press sleeve
Locking strip
Installing sleeve
Assembly drift
Installing tool 8
Installing tool
Hook
Torque wrench
Torque wrench
1121 893 2400
0000 893 5904
4119 893 4600
1130 893 4700
5910 890 2208
1116 893 4800
5910 893 8800
5910 890 0302
5910 890 0312
Testing engine and carburetor for leaks
Sealing the exhaust port
Testing carburetor for leaks
Testing carburetor for leaks
Removing limiter caps
Adjusting carburetor
Add-on for screwdriver (adjusting
carburetor)
Removing flywheel nut
Adjusting air gap between the ignition
module and flywheel
Testing ignition system
Testing ignition system
Removing oil seals
Removing oil seal(s)
Holding the engine pan
Holding engine pan with puller
5910 890 4400
Installing oil seals
Blocking the crankshaft
Protects oil seal at fan side
Removing and installing piston pin
Installing hookless snap ring in piston
Rewind spring
Removing pickup body
0.5 to 18 Nm
6 to 80 Nm
3
4
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Rem.
81
No.
Part Name
Part No.
Application
Rem.
20
Screwdriver bit, T 27 x 125
0812 542 2104
21
22
Screwdriver bit, T 27 x 150
Crimping tool
5910 890 2400
5910 890 8210
1
Removing and installing spline socket
screws with electric or pneumatic
screwdrivers; tighten down screws with
torque wrench (4 mm)
IS-P screws (4 mm)
1
Attaching connectors to electrical wires
Remarks
1) Use for releasing only.
82
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
13.
Servicing Aids
No.
Part Name
Part No.
Application
1
Lubricating grease (225 g tube)
0781 120 1111
Oil seals, sliding and bearing points
2
STIHL special lubricant
0781 417 1315
Bearing bore in rope rotor, rewind spring in fan
housing
3
Press Fluid OH 723
0781 957 9000
Rubber elements, fuel hoses, etc.
4
STIHL multipurpose grease
0781 120 1109
High voltage output on ignition module
5
Dirko HT red sealant
0783 830 2000
Crankcase, oil seals (outside)
5
Medium-strength threadlocking
adhesive (Loctite 242)
0786 111 2101
6
High-strength threadlocking
adhesive (Loctite 270)
0786 111 2109
7
High-strength threadlocking
adhesive (Loctite 648)
0786 111 2117
8
Standard commercial solventbased degreasant containing no
chlorinated or halogenated
hydrocarbons
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
Cleaning sealing faces and carburetor,
crankshaft stubs and flywheel taper
83
84
BG 56, BG 66, BG 66 C, BG 86, SH 56, SH 86
englisch / English
0455 296 0123. M7. C8. FST. Printed in Germany