Stihl 029, 039 Service manual

STIHL 029, 039 1

Service Manual
029 and 039
Chain Saws

Chain saw on assembly stand

As the design concept of these two
models is almost identical, the
descriptions and servicing pro­cedures in this manual generally
apply to both. Differences are
described in detail.

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.
Microfilmed parts list are always
more up to date than printed lists.

A fault on the machine may have
several causes. Consult the
"Troubleshooting Charts" when
tracing faults.

Refer to the "Technical Informa­tion" bulletins for engineering
changes which have been intro­duced since publication of this
service manual.

Service manuals and technical
information bulletins describing
engineering changes are intended
exclusively for the use of STIHL
servicing dealers and staff and
must not be passed on to third
parties.

Servicing and repairs are made
considerably easier if the saw is
mounted on assembly stand 5910
850 3100 or 5910 890 3100. This
enables the saw to be swivelled to
the best position for the ongoing
repair and leaves both hands free.

The saw can be quickly secured to
the stand by means of the bar
mounting studs and nuts (after
removing the sprocket cover).

The STIHL Special Tools manual
lists all special servicing tools
currently available from STIHL.

Always use original STIHL
replacement parts.

Original STIHL parts can be
identified by the STIHL part
number, the

the STIHL parts symbol
symbol may appear alone on small
parts.

STIHl

STIHl

STIHlSTIHl

logo and

(

The

STIHl

STIHl

STIHlSTIHl

© 1992 Andreas Stihl. Waiblingen

STIHL 029, 039 2

CONTENTS

1. Specifications 35. Ignition System 37 11. Fuel System 58

1.1 Engine 3 5.1 Repairing Component 11.1 Air Filter 58

1.2 Fuel System 4 Parts 37 11.2 Removing and Installing

1.3 Ignition System 4 5.1.1 Spark Plug 37 the Carburetor 59

1.4 Cutting Attachment 5 5.1.2 Ignition Module 39 11.3 Leakage Testing

1.5 Special Accessories 5 5.1.2.1 Ignition Timing 39 the Carburetor 60

1.5.1 For User 5 5.1.2.2 Removing and Installing 39 11.4 Servicing the

1.5.2 For Service 5 5.1.3 Spark Plug Terminal 41 Carburetor 60

1.6 Tightening Torques 6 5.1.4 Ignition Lead 42 11.5 Carburetor Adjustment 66

5.1.5 Flywheel 42 11.6 Automatic Choke 68

2. Troubleshooting 5.1.6 Short Circuit Wire/ 11.6.1 Description of Operation 68
Charts 7 Ground Wire 44 11.6.2 Troubleshooting Chart 69

5.1.7 Contact Spring 44 11.6.3 Testing Automatic

2.1 Clutch, Chain Drive, Choke 70
Chain Brake and 6. Rewind Starter 45 11.6.4 Leakage Testing
Chain Tensioner 7 Engine Housing

2.2 Engine 8 6.1 Routine Maintenance 45 and Control Valve 70

2.3 Ignition System 9 6.2 Rope Rotor/Pawl 45 11.6.5 Testing Control Valve

2.4 Rewind Starter 10 6.3 Replacing the (removed from machine) 71

2.5 Chain Lubrication 11 Starter Rope 46 11.6.6 Leakage Testing

2.6 Fuel System 12 6.4 Replacing the the Bellows 72

Rewind Spring 47 11.6.7 Foam Filter/

3. Clutch, Chain Drive, 6.5 Tensioning the Polymer Sintered Filter 72

Chain Brake and Rewind Spring 47 11.6.8 Removing and Installing
Chain Tensioner 14 6.6 Replacing Starter the Carburetor 73

Rope Guide Bush 48 11.6.9 Removing and Installing

3.1 Clutch Drum and Lever System on
Chain Sprocket 14 7. AV Handle System 49 Carburetor 73

3.2 Clutch 15 11.6.10 Throttle Shaft/

3.3 Chain Brake 17 7.1 Repair 49 Choke Shaft 76

3.3.1 Disassembly 17 11.6.11 Hose/Connector 77

3.3.2 Assembly 19 11.6.12 Control Valve 77

3.4 Front Chain 8. Handle Housing 50 11.6.13 Bellows 78

Tensioner 21 11.7 Tank Vent 79

3.5 Side Chain 8.1 Front Handle 50 11.8 Fuel Pickup Body and
Tensioner 21 8.1.1 Removing and Installing Fuel Hose 79

3.6 Bar Mounting Studs 22 Handle Housing 50 11.9 Replacing the

FuelTank 80

4. Engine 23 9. Master Control 53

12. Special Servicing 82

4.1 Removing and Refitting 9.1 Switch Shaft 53 Tools and Aids
Exhaust Muffler 23 9.2 Interlock Lever/

4.2 Leakage Testing Throttle Trigger 54 12.1 Special Servicing Tools 82
the Engine 24 12.2 Servicing Aids 83

4.2.1 Preparations 24 10. Chain Lubrication 55

4.2.2 Pressure Test 25

4.2.3 Vacuum Test 26 10.1 Suction Hose/

4.3 Replacing the Pickup Body 55
Oil Seals 27 10.2 Vent Valve 56

4.4 Removing and Installing 10.3 Removing and Installing
the Engine 29 the Oil Pump 56

4.5 Cylinder 30 10.4 Servicing the

4.6 Piston 33 Oil Pump 57

4.7 Piston Rings 35

4.8 Crankshaft 36

STIHL 029, 039 3

1. SPECIFICATIONS

1.1 Engine 029 039

STIHL single-cylinder two-stroke engine with special

impregnated cylinder bore

Displacement: 54.1 cm3 (3.3 cu.in) 64.1 cm3 (3.9 cu. in)

Bore: 45 mm (1.77 in) 49 mm (1.93 in)

Stroke: 34 mm (1.34 in) 34 mm (1.34 in)

Compression ratio: 9.5:1 10:1

Power output: 2.70 kW (3.7 bhp) 3.20 kW (4.4 bhp)

Max. torque: 2.8 Nm (2.1 lb. ft) 3.4 Nm (2.5 Ib. ft)

at 6,500 r.p.m. at 6,500 r.p.m.

Max. permissible engine

speed with bar and chain: 13,000 r.p.m. 13,000 r.p.m.

Mean idle speed: 2,700 r.p.m. 2,700 r.p.m.

Crankshaft: Three-part, Three-part,

drop forged drop forged

Crankshaft bearings: 2 ball bearings 2 ball bearings

Crankpin dia.: 14.4 mm (0.55 in) 14.4 mm (0.55 in)

Big-end bearing: Needle cage Needle cage

Conrod length: 58 mm (2.28 in) 58 mm (2.28 in)

Piston pin diameter: 10 mm (0.39 in) 10 mm (0.39 in)

Small-end bearing: Needle cage Needle cage

Rewind starter: Pawl system with Pawl system with

automatic rope automatic rope

rewind mechanism rewind mechanism

Starter rope: 3.5 mm (0.14 in) dia., 3.5 mm (0.14 in) dia.,

960 mm (37.8 in) long 960 mm (37.8 in) long

Clutch: Centrifugal clutch Centrifugal clutch

without linings, without linings,

76 mm (3.0 in) dia. 76 mm (3.0 in) dia.

Clutch engages at: approx. 3,500 r.p.m. approx. 3,500 r.p.m.

Crankcage leakage test

at gauge pressure: 0.4 bar (5.8 psi) 0.4 bar (5.8 psi)

under vacuum: 0.4 bar (5.8 psi) 0.4 bar (5.8 psi)

STIHL 029, 039 4

1.2 Fuel System 029 / 039

Carburetor: All position diaphragm

carburetor with integral fuel

pump
Standard setting
High speed adjusting screw H: Back off approx. 1 turn
Low speed adjusting screw L: Back off approx. 1 turn

(starting with screws tight

against their seats)
Carburetor leakage test
at gauge pressure: 0.4 bar (5.8 psi)
Fuel tank capacity: 0.56 L (1 .2 US pt)
Fuel mixture: Regular brand-name gasoline

and brand-name two-stroke

engine oil
Mix ratio: 50:1 with Stihl two-stroke

engine oil

25:1 with other brand-name

two-stroke brand-name,

air-cooled engine oils
Air filter: Prefilter (coarse filter)

bisectional box filter

1.3 Ignition System

Type: Electronic magneto ignition

(breakerless) with integral

trigger unit
Air gap: 0.15-0.3 mm (0.006-0.012 in)
Ignition timing: 2.0-2.8 mm (0.08-0.10 in) B.T.D.C.

at 8,000 r.p.m.
Advance angle: 24.5-29.5° B.T.D.C.

at 8,000 r.p.m.
Spark plug (suppressed): Bosch WSR 6 F or

NGK BPMR 7 A
Electrode gap: 0.5 mm (0.020 in)
Spark plug thread: M14x1.25
Length of thread: 9.5 mm (0.37 in)
Heat range: 200

STIHL 029, 039 5

1.4 Cutting Attachment

Guide bars: Rollomatic with sprocket nose

Duromatic with stellite-tipped nose

Bar tail: 3003

Bar lengths: (32, 37, 40, 45, 50 and 63 cm)

(13, 15, 16, 18 and 25 in)

Oilomatic chain: 9.32 mm (3/8") Rapid-Micro,

Rapid-Super

8.25 mm (0.325") Rapid-Micro,

Rapid-Super

Chain sprockets: 7-tooth 3/8" spur sprocket

7-tooth 0.325" spur sprocket

7-tooth 0.325" rim sprocket

8-tooth 0.325" rim sprocket

Chain speed: 21.7 m/s (71 ft/s) at 10,000 r.p.m.

Chain lubrication: Fully automatic, speed-controlled

reciprocating oil pump, no feed at

idle speed. Additional manual oil flow

control

Oil feed rate (adjustable): 6-15 cm³/min (0.2 - 0.5 fl.oz/min)

at 10,000 r.p.m.

Oil tank capacity: 0.33 L (0.7 US pt)

1.5 Special Accessories

1.5.1 For user STIHL repair kit 1127 900 5000
Starter rope ∅ 3.5x30.5 m 0000 930 2203
7-tooth 3/8" rim sprocket kit 1125 007 1002
7-tooth 0.325" rim sprocket kit 1125 007 1001
8-tooth 0.325" rim sprocket kit 1125 007 1000
7-tooth 3/8" spur sprocket 1125 640 2000
7-tooth 0.325" spur sprocket 1125 640 2005
Spur gear/tensioning screw kit 1127 007 1003
Elastostart 1128 190 3400

1.5.2 For service shop Carburetor parts kit (Walbro) 1127 007 1060
Carburetor parts kit
(automatic choke) 1127 007 1061

STIHL 029, 039 6

1.6 Tightening Torques

"DG" screws are used in the polymer and light-alloy components of models 029 and 039. When screwed in for the
first time, DG screws form a permanent thread in the parts concerned. They can be released and retightened as often
as necessary without affecting the strength of the screwed assembly. However, it is essential to always use a torque
wrench to tighten the screws to the specified torques.

Fastener Thread For component Torque Remarks

size Nm (Ibf.ft)

Spline screw IS-DG4x15 Chain tensioner cover/

engine housing 3.2 (2.4)

Spline screw IS-DG4x15 Chain brake cover/

engine housing 3.2 (2.4)
Spline screw IS-DG4x15 Handle housing/handle molding 1.6 (1.2)
Spline screw IS-DG4x15 Oil pump 4.0 (3.0)
Spline screw IS-DG4x15 Shroud/engine housing 3.2 (2.4)
Spline screw IS-DG4x15 Ground wire to cylinder 4.0 (3.0)
Spline screw IS-DG5x16 Chain catcher/engine housing 3.5 (2.6)
Spline screw IS-DG5x16 Spiked bumper/engine housing 3.5 (2.6)
Spline screw IS-DG5x24 Front handle/handle housing 3.5 (2.6)
Spline screw IS-DG5x24 Hand guard (I/h) with sleeve 3.5 (2.6)
Spline screw IS-DG5x24 Fan housing/engine housing 3.5 (2.6)
Spline screw IS-DG5x24 Buffer/front handle 3.5 (2.6)
Spline screw IS-DG5x24 Buffer/engine housing 3.5 (2.6)
Spline screw IS-DG5x24 Ignition module/engine housing 4.8 (3.5)
Spline screw IS-DG6x52 Engine housing/cylinder 11.0 (8.1)

M12x1L Carrier (clutch) 50.0 (37.0)
Collar stud DG8x24 Guide bar 16.0 (11.8)
Collar stud M10x21 Guide bar/engine pan 30.0 (22.0) 1)

M14x1.25 Spark plug 25.0 (18.5)
Hexagon nut M5 Muffler 9.0 (6.6)
Hexagon nut M5 Box filter/carburetor 2.0 (1.5)
Hexagon nut M5 Carburetor with box filter 3.2 (2.4)
Hexagon nut M8x1 Flywheel 27.5 (20.3)

Use the following procedure to fit a DG screw in an existing thread:

- Place the DG 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.

Remarks:

1) Screw must be secured with adhesive 0786 110 0126 (Loctite 649).

Note: Screws secured with adhesive are easier to release if the adhesive is heated first with a hot air blower (hair
dryer). Exercise caution on polymer components.

STIHL 029, 039 7

2. TROUBLESHOOTING
CHARTS

2.1 Clutch,
Chain Drive,
Chain Brake and
Chain Tensioner

Condition Cause Remedy

Saw chain turns at idle speed Engine idle speed too high Readjust at idle speed

adjusting screw
(counterclockwise)

Spring hooks broken Fit new springs

Loud noises Clutch springs stretched or Replace all clutch springs

fatigued

Needle cage damaged Fit new needle cage

Clutch shoe retainer broken Fit new retainer

Clutch shoes and carrier Fit new clutch
worn

Chain sprocket wears Chain not properly Tension chain as specified
rapidly tensioned

Chain wears rapidly Chain not properly Tension chain as specified

tensioned

Poor chain lubrication Check chain lubrication and

rectify problem

Worn chain sprocket Fit new sprocket

Chain does not stop Brake spring broken Fit new brake spring
immediately when brake is
activated Brake band stretched or Fit new brake band

broken

STIHL 029, 039 8

2.2 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, Oil seals between cylinder Replace oil seals
stalls at idle speed, but operates and engine pan damaged
normally at full throttle

Manifold leaking Seal or replace manifold

Engine pan leaking Seal engine pan

Engine pan damaged (cracks) Replace engine pan

Engine does not deliver full Secondary air seepage through Mount manifold correctly or
power or runs erratically poorly mounted or faulty replace

manifold

Piston rings leaking or Fit new piston rings
broken

Muffler carbonized Clean muffler (inlet

and exhaust), replace spark
arresting screen (if fitted)

Engine overheating Insufficient cylinder Thoroughly clean all cooling

cooling. Air inlets in fan air openings
housing blocked or cooling fins
on cylinder very dirty
Intake air preheating being Move shutter to
used at too high an outside summer position

temperature

STIHL 029, 039 9

2.3 Ignition System

Warning: 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!

Spark plug terminal firmly seated on spark plug?

yes

Remove spark plug.
Is it in good condition?

no

Clean spark plug and reset electrode gap.
Does spark test produce powerful spark?

Replace faulty ignition lead of short circuit wire.
Repair contact spring or switch shaft.

Insert screwdriver in place of spark plug in spark plug
terminal and hold about 4 mm (1/8") away from
ground. Sparkover?

no

no

yes

no

Press terminal firmly onto spark
plug and fit spring if necessary.

Faulty insulation on ignition
lead or short circuit wire?
Is connector sleeve touching short circuit
contact?

yes

yes

no

no

Adjust air gap (0.15 - 0.3 mm).
Is spark test positive?

Use ohmmeter to check ignition lead
for break. If break is detected, replace
ignition lead. Does spark test now
produce sparkover?

no

Replace ignition module. Does engine
now run after positive spark test?

yes

no

no

no

Fit new spark plug.Is air gap correct?

Does flywheel appear to be
in good condition?

yes

Fit new flywheel.
Is spark test positive?

Ignition system in order.
Look for fault in fuel system and
carburetor.

no

STIHL 029, 039 10

y

2.4 Rewind Starter

Condition Cause Remed

Starter rope broken Rope pulled out too vigorously as Fit new starter rope

far as stop or over edge - i.e.
not vertically

Normal wear Fit new starter rope

Rewind spring broken Spring overtensioned - Fit new rewind spring

no reserve when rope is fully
extended

Very dirty or corroded Fit new rewind spring

Starter rope can be pulled out Guide peg on pawl or pawl Fit new pawls
almost without resistance itself worn
(crankshaft does not turn)

Spring clip fatigued Fit new spring clip

Starter rope is difficult to Starter mechanism is very Thoroughly clean complete
pull and rewinds very slowly dirty (dusty conditions) starter mechanism

Lubricating oil on rewind spring Apply a few drops of kerosine
becomes viscous at very low (paraffin) to spring, then pull
outside temperatures (spring rope carefully several times
windings stick together) until normal action is

restored

STIHL 029, 039 11

2.5 Chain Lubrication

Important: In the event of trouble with the chain lubrication system, always investigate the other possible sources

of faults before disassembling the oil pump.

Condition Cause Remedy

Chain receives no oil Oil tank empty Fill up with oil

Oil inlet hole in guide bar Clean oil inlet hole
is blocked

Intake hose or pickup body Wash intake hose and pickup
(strainer) clogged or intake body (strainer) in white spirit
hose ruptured and blow out with compressed air;

replace if necessary

Valve in oil tank blocked Clean or replace valve

Teeth on pump piston and/or Fit new oil pump and/or
worm worn new worm

Machine losing chain oil Bore in pump Fit new pump housing

housing worn

Oil pump delivers too Control screw and/or Fit new control screw and/or
little oil control edge on pump piston pump piston

worn

Bore in pump housing Fit new pump housing
worn

STIHL 029, 039 12

2.6 Fuel System

Note: For machines with automatic choke see 11.6.2.

Condition Cause Remedy

Carburetor floods; Inlet needle not sealing. Remove and clean or replace
engine stalls Foreign matter in valve seat or inlet needle,

cone damaged clean fuel tank, pickup body and

fuel line if necessary
Inlet control lever sticking on Free off inlet control lever
spindle
Helical spring not located on Remove inlet control lever
nipple of inlet control lever and refit correctly
Perforated disc on diaphragm Fit new metering diaphragm
is deformed and presses constantly
against inlet control lever
Inlet control lever too high Set inlet control lever flush
(relative to design position) with bottom of metering chamber

Poor acceleration Idle jet "too lean" Back off low speed adjusting

screw slightly

(see Carburetor Adjustment)
Main jet "too lean" Back off high speed adjusting

screw slightly

(see Carburetor Adjustment)
Inlet control lever too low Set inlet control lever flush
(relative to design position) with bottom of metering chamber
Inlet needle sticking to valve Remove inlet needle, clean
seat and refit
Connecting bore to atmosphere Clean bore
blocked
Diaphragm gasket leaking Fit new diaphragm gasket
Metering diaphragm damaged Fit new metering diaphragm
or shrunk

Engine will not idle, Throttle shutter opened too wide Reset idle speed adjusting screw
idle speed too high by idle speed adjusting screw correctly

STIHL 029, 039 13

Condition Cause Remedy

Engine stalls at idle speed Idle jet bores or ports Clean jet bores and ports

blocked with compressed air

Idle jet "too rich" Screw down low speed adjusting

screw slightly
(see Carburetor Adjustment)

Setting of idle speed Set idle speed adjusting
adjusting screw incorrect screw correctly

- throttle shutter completely
closed

Small plastic plate in valve Clean or renew valve jet
jet does not close

Engine speed drops quickly under Air filter plugged Clean air filter
load - low power

Tank vent faulty Clean or replace tank vent

if necessary

Leak in fuel line between tank Seal or renew connections
and fuel pump and fuel line

Pump diaphragm damaged or Fit new pump diaphragm
fatigued

Main jet bores or ports Clean bores and ports
blocked

Fuel pickup body dirty Clean pickup body, fit new

filter

Fuel strainers dirty Clean fuel strainers

See also 2.2

STIHL 029, 039 14

3. CLUTCH, CHAIN DRIVE
CHAIN BRAKE AND
CHAIN TENSIONER

3.1 Clutch Drum and
Chain Sprocket

Top:
Removing needle cage

Bottom:
Assembly sequence of chain drive

Top: Top: 2 = Needle cage
Sprocket cover mounting nuts Removing E-clip 3 = Washer

Bottom: Bottom: 5 = Clutch drum (for rim sprocket)
Disengaging chain brake Removing chain sprocket 6 = Rim sprocket

1 = Spur sprocket

4 = E-clip

- Unscrew sprocket cover nuts - Remove the washer from the Note: Clean stub of crankshaft.
and remove the sprocket cover. clutch drum or chain sprocket. Replace the needle cage or wash

it in clean white spirit and lubricate

- Disengage the chain brake by - Remove the spur sprocket or rim with STIHL multipurpose grease,
pulling the hand guard back sprocket with clutch drum. see 12.2.
toward the front handle.

- Take the needle cage out of the Push clutch drum/chain sprocket

- Pry the E-clip off the crankshaft. clutch drum or chain sprocket. onto crankshaft and rotate it until

tang of spring on oil pump worm
Reassemble in the reverse engages the notch in the clutch
sequence. drum.

Important: Rim sprocket must be

fitted with the chip ejector cavities

facing outward.

STIHL 029, 039 15

3.2 Clutch

Top:
Removing prefilter Top: Top:

Bottom:
1 = Spark plug terminal Bottom: Bottom:
2 = Spark plug Locking strip in position Assembly hook 5910 890 2800

Locking strip 0000 893 5902 Unscrewing the clutch

Removing and disassembling - Push the locking strip into the - Remove the clutch drum or chain
clutch: spark plug hole so that "TOP" or sprocket, see 3.1.

"OBEN" is facing upward.

Troubleshooting chart - see 2.1. - Unscrew the clutch from the

Important: To avoid the risk of stub of the crankshaft.

- Remove air filter - see 11.1. piston damage, use only the
specified locking strip. Caution: Clutch has a left-hand

- Pull the prefilter out of the handle thread.

housing.

- Pull terminal off the spark plug.

Unscrew the spark plug.

STIHL 029, 039 16

Top:

Top: clutch shoe Top:
Removing a clutch spring Clutch clamped in a vise

Bottom: Pushing clutch shoe Bottom:
Component parts of clutch onto carrier Attaching clutch springs

Fitting retainer on

Bottom:

- Use assembly hook to remove all Assembling and installing - Clamp the clutch, e.g. one shoe,
the clutch springs. the clutch: in a vise.

- Pull the clutch shoes off the - Slip the retainers onto the clutch - Attach one end of each spring to
carrier. shoes so that the narrow side is the clutch shoes by hand.

next to the series number, e.g.

- Pull the retainers off the clutch 1127. - Use the assembly hook to attach
shoes. the other ends of the springs and

- Fit the clutch shoes over the press them firmly into the clutch

- Clean all parts and stub of arms of the clutch carrier so that shoes with one finger.
crankshaft in white spirit. the series number, e.g. 1127, is
Replace any damaged or worn on the same side as the carrier's
parts. hexagon.

STIHL 029, 039 17

3.3 Chain Brake

3.3.1 Disassembly

Top: Top: Top:
Tightening the clutch Bumper strip Detaching brake spring

Bottom: Bottom: Bottom:
Fitting the prefilter Cover mounting screws Removing the brake band

- Screw clutch onto crankshaft - Remove the clutch drum or spur - Carefully remove the brake
and torque down to 50 Nm sprocket - see 3.1. spring from the anchor pin.
(37 Ibf.ft).

- Engage the chain brake. - Ease the brake band out of its

- Install clutch drum or spur seat in the engine housing.
sprocket - see 3.1 - Remove the upper bumper strip

from its seat.

- Remove locking strip from

cylinder. Install spark plug - Remove mounting screws from
and torque down to 25 Nm cover and lift cover away.
(18.5 Ibf.ft).

- Install the air filter - see 11.1.

- Fit the prefilter so that its tabs

engage the recesses in the
handle housing.

STIHL 029, 039 18

p)

Top:
Removing the Top:
brake band Top: Washer on pivot pin

Bottom: Bottom:
Hand guard mounting Bottom: 1 = Hand guard
screw Removing the link (stra

E-clip on bell crank pivot pin

2 = Bell crank

- Remove the brake band from the - Pry the E-clip off the bell crank - Remove washer from bell crank
retaining lug and disconnect it pivot pin. pivot pin.
from the bell crank.

- Remove the link (strap) from the - Carefully pull the hand guard and

- Take out the hand guard moun- bell crank pivot pin. bell crank off their pivot pins and
ting screw. lift them away together.

- Slide the link up and take it off
the hand guard pivot pin.

STIHL 029, 039 19

A

3.3.2

Top:
1 = Spring Top:
2 = Cam lever Pressing cam lever
3 = E-clip downward

Bottom: Bottom:

Disconnecting the spring hand guard of hand guard

Fitting bell crank in Correct installed position

ssembly

- Remove the E-clip from the cam
lever pivot pin.

- Disconnect spring from the cam

lever. Pull the cam lever off the
pivot pin.

- Remove the spring.

- Clean all disassembled parts in
white spirit. Replace any worn or
damaged parts.

- Push the cam lever onto the pivot - Position bearing boss of hand
pin and secure it with the E-clip. guard against the pivot pin and fit

the other side of the hand guard

- Attach the spring to the cam over the handle housing.

lever, from behind, and push it

over the pivot pin. - Press the cam lever downward

and push the hand guard and

- Insert the bell crank in the side of bell crank onto the pivot pins.
the hand guard so that the short
arm of the bell crank points up.

STIHL 029, 039 20

Top: Top:
Fitting the link Top: Assembly tube 1117 890 0900

Bottom: Bottom:
Attaching brake band to bell Bottom: Attaching brake spring to
crank Attaching the brake spring anchor pin

Fitting the brake band

- Fit the washer on the bell crank Important: Coat sliding and - Slip the bush over the hand
pivot pin. bearing points with Molykote guard mounting screw. Fit screw

grease - see 12.2. Do not and tighten to 3.5 Nm (2.6 Ibf.ft).

- Position the link on the hand lubricate the brake band.
guard pivot pin and slide it down - Fit cover for brake band.
until it engages the groove on the - Attach the brake spring to the
end of the pivot pin. Then push bell crank. - Fit bumper strip in its seat.
link over the bell crank pivot pin
and secure it with the E-clip. - Use the assembly tool and a - Install the clutch drum or chain

screwdriver to attach the brake sprocket - see 3.1.

- First attach brake band to bell spring to the anchor pin.
crank and then push it into the
engine housing recess.

STIHL 029, 039 21

r

3.4 Front Chain
Tensione

Top:
1 = Adjusting screw Top:
2 = Adjusting nut Cover mounting screw

Bottom: b = 1.7 mm (0.07") Bottom:
Removing cover c = ∅ 10 mm (0.4") Removing the chain tensioner

a = 19.5 mm (0.77")

3.5 Side Chain

Tensioner

- Remove chain sprocket cover.

- Unscrew the adjusting nut by
rotating the adjusting screw.

- Take the adjusting screw out of
the cover and housing.

- Pull the cover out of the engine
housing.

Note: The front chain tensioner can
be converted to a side chain
tensioner - see 3.5.

In the case of a coversion from
front to side chain tensioner, it is
necessary to drill a hole in the
sprocket cover to take the peg of the
spur gear - see dimensions in
illustration.

Reverse the above sequence to
install the chain tensioner.

- Remove the chain sprocket cover.

- Take out the cover mounting
screw.

- Pull the chain tensioner assem-

bly out of the engine housing.

STIHL 029, 039 22

3.6 Bar Mounting
Studs

Top:
1 = Thrust pad
2 = Tensioner slide
3 = Adjusting screw
4 = Spur gear
5 = Cover

Bottom: Removing tensioner slide Unscrewing collar stud with
Withdrawing the spur gear and adjusting screw stud puller 5910 893 0501

- Take the thrust pad off the
adjusting screw.

- Rotate spur gear until the
adjusting screw comes is clear
of the tensioner slide.

- Pull the spur gear out of the
cover.

- Pull the tensioner slide off the - Remove the sprocket cover.
cover.

- Push the stud puller over the

- Take the adjusting screw out of front collar stud (next to spiked
the cover. bumper) as far as it will go. Use

a 15 mm wrench to unscrew the

- Inspect the teeth on the spur collar stud counterclockwise.
gear and adjusting screw. If the
teeth are damaged, replace both - Fit the collar stud and torque it
parts. down to 16 Nm (11.8 Ibf.ft).

Note: The collar stud next to the
Reverse the above sequence to chain sprocket is installed with
install the chain tensioner. Loctite.

Note: Coat teeth of adjusting - Remove the muffler - see 4.1.
screw and spur gear with grease,
see 12.2, before refitting. - Use hot air blower (e.g. hair

dryer) to heat engine pan around
the collar stud. Then unscrew the
collar stud with the stud puller.

- Coat thread of collar stud with
Loctite, see 12.2.

- Fit collar stud and torque it down
to 30 Nm (22 Ibf.ft).

- Install the muffler - see 4.1.

STIHL 029, 039 23

g

4. ENGINE

4.1 Removing and Refitting

Exhaust Muffler

Top:
Flanged locknuts on muffler

Bottom:
Removing the muffler

Top:
Removing the cover

Bottom:
Removing the spark arresting screen

Top:
Gasket

Bottom:
Removin

the screws

These machines do not have a
conventional crankcase - the engine
consists of the cylinder, piston,
crankshaft and engine pan.

Troubleshooting chart - see 2.2.

- Unscrew flanged locknuts from
muffler.

- Remove muffler together with cover.

- Remove the cover from the
muffler.

- Remove the spark arresting
screen, if fitted, from the muffler.

- Clean the spark arresting screen or
fit a new one if necessary.

- Remove the gasket.

- Take the mounting screws out of
their seats on the cylinder.

Reassemble in the reverse
sequence.

Note: Install a new gasket. Use new
flanged locknuts and tighten them
down to 8.5 Nm (6.2 Ibf.ft).

STIHL 029, 039 24

4.2 Leakage Testing

the Engine

Top:
Carburetor and crankcase tester
1106 850 2905

Bottom:
Vacuum pump 0000 850 3500

4.2.1 Preparations

Top:
1 = Sealing plate 0000 855 8106
2 = Flange 1123 855 4200
3 = Sleeves 1127 851 8300

Bottom:
Sealing plate between
mounting screws

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 thus upset the fuel-air
mixture.

This makes adjustment of the
prescribed idle speed difficult, if
not impossible.

Moreover, the transition from idle
speed to part or full throttle is not
smooth.

The engine housing can be checked
accurately for leaks with the
carburetor and crankcase tester and
the vacuum pump.

- Remove the muffler - see 4.1.

- Position the sealing plate
between the mounting screws.

STIHL 029, 039 25

4.2.2 Pressure Test

Top:

Top:
Flange 1123 855 4200 fitted in position

Bottom:
Test flange 1128 850 4200

1 = Bore No. 1
2 = Bore No. 2

Bottom:
Test flange fitted in position
(pin in impulse hose)

Top:
Tester's pressure hose fitted on test flange nipple

Bottom:
Closing the vent screw

- Fit the flange in place of the
muffler.

- Push the sleeves over the mounting
screws. Fit the nuts and tighten
them firmly.

Note: Sealing plate must completely
fill the space between the two
mounting screws.

- Remove carburetor - see 11.2.

- Set the piston to top dead center
(T.D.C.). This can be checked
through the inlet port.

- Check to see that the pin in the
test flange is in bore No. 1 and
fit it if necessary.

- Fit the test flange in place of the
carburetor.

Important: When fitting the test
flange, make sure the pin is
properly located in the impulse
hose.

- Connect tester's pressure hose
to nipple on test flange.

- Make sure the spark plug is
properly tightened down before
starting the test.

- Close the vent screw on the
rubber bulb.

- Use rubber bulb to pump air into
the engine housing until the gauge
shows a pressure of 0.4 bar
(5.8 psi). If this pressure remains
constant for at least 20 seconds,
the engine housing is airtight.

STIHL 029, 039 26

g

4.2.3 Vacuum Test

Pressure-testing the engine

Tester's suction hose connected
to nipple on test flan

e

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.

An additional test can be carried out
with the vacuum pump to detect this
kind of fault. The preparations for this
test are the same as for the pressure
test - see 4.2.1.

However, if the indicated pressure
drops, the leak must be located and
the faulty part replaced. Note: Coat
the suspect area with oil and
pressurize the engine housing
again. Bubbles will appear if there is
a leak in the oiled area.

- Carry out the vacuum test - see

4.2.3.

- After finishing the tests, open the
vent screw and disconnect the
hose.

- Remove the test flange and refit
the carburetor - see 11.2.

- Remove the flange and sealing
plate.

- Refit the muffler - see 4.1.

- Connect the vacuum pump's suction
hose to test flange nipple.

- Pull out the pump piston several
times until the gauge indicates a
vacuum of 0.4 bar (5.8 psi).

STIHL 029, 039 27

4.3 Replacing the

Oil Seals

Top:
Puller 0000 890 4400 with
No. 6 jaws 0000 893 3711

Bottom:
Removing oil seal at

Leakage test with vacuum pump

clutch side

Note: When you release the pump
piston, the non-return valve auto­matically seals the suction hose. If the
vacuum reading remains constant, or
rises to no more than 0.3 bar
(4.25 psi) 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 crankcase),
the oil seals must be replaced, even if
no leaks were

detected in the pressure test.

- Remove the test flange and refit
the carburetor - see 11.2.

- Remove the flange and sealing
plate.

- Refit the muffler - see 4.1.

Note: If oil seals have to be
replaced - see 4.3.

It is not necessary to disassemble
the complete engine to replace the
oil seals.

Clutch side:

- Remove the oil pump - see 10.3.

- Apply the puller and withdraw the
oil seal at the clutch side.

STIHL 029, 039 28

g

Top:
Installing oil seal with press sleeve

Replacement oil seal
1 = Sealing lip
2 = Cla mping ri ng
3 = Dust lip

1127 893 2400

Bottom:
Removing oil seal at
i

nition side

Installing oil seal without
press sleeve

Note: Take care not to damage the
crankshaft in the area of the oil seal.
If new oil seals have already been
installed, use sealing ring puller and
No. 3.1 jaws to pull out the clamping
ring. Pry the remaining part of the oil
seal out of the housing.

- Clean the sealing surface with a
solvent-based degreasant
containing no CFCs.

- Pack space between sealing and
dust lips with grease - see 12.2.

- Apply thin coating of sealant, see

12.2, to outside diameter of the oil
seal.

- Slip the assembly sleeve 1122
893 4600 over the end of the
crankshaft.

- Position oil seal so that the
clamping ring points up. Use the
press sleeve to press home the oil
seal as far as stop.

- Wait about one minute and then
rotate the crankshaft several
times.

- Remove the assembly sleeve.

- Install the oil pump - see 10.3.

Ignition side:

- Remove the flywheel - see 5.1.5.

Note: Remove oil seal with
clamping ring as described for
clutch side.

- Clean the sealing surface with a
solvent-based degreasant
containing no CFCs, and apply thin
coating of sealant, see 12.2, to
outside diameter of oil seal.

- Pack space between sealing and

dust lips with grease - see 12.2.

- Position the oil seal so that the
clamping ring points up. Use the
press sleeve to to press home the
oil seal as far as stop.

Note: If the press sleeve is not
available, the oil seals can be
pressed into the housing by hand.

- Wait about one minute and then
rotate the crankshaft several times.

- Fit the flywheel - see 5.1.5.

- Apply the puller and withdraw the oil
seal at the ignition side.

STIHL 029, 039 29

y

g

g

4.4 Removing and Installing

the Engine

1 = Spark plug terminal
2 = Spark plug

nition lead retainer

3 = I

Always check and, if necessary, repair
the fuel system, carburetor, air filter
and ignition system before looking for
faults on the engine.

Top:
Cover mounting
screws

Bottom:
Ground wire
fastening screw

Top:
Bar mounting
stud

Bottom:
Engine housing /engi ne
mountin

screws

- Remove handle housing see

8.1.1.

- Remove the flywheel - see 5.1.5.

- Remove the oil pump - see 10.3.

- Remove the muffler - see 4.1.

- Pull the terminal off the spark plug
and unscrew the spark plug.

- Remove the ignition lead from

the retainer and groove on the
cover.

- Take out the cover mounting
screws and lift the cover away.

- Remove the ground wire
fastening screw from the
cylinder.

- Remove the collar stud next to
the brake band.

Important: The collar stud is installed
with Loctite. Use hot air blower (e.g.
hair dryer) to heat engine pan around
the collar stud.

- Remove the engine pan mounting

screws from the c

linder.

STIHL 029, 039 30

4.5 Cylinder

Top:
Removing the engine

Bottom:
Sequence for tightening screws

Correct position of ignition lead
in cover
1 = Tank v ent

- Fit mounting screw 1 as far as
stop.

- Coat thread of collar stud 4 with
Loctite - see 12.2.

Top:
Impulse hose

Bottom:
1 = Hose clamp
2 = Manifold

- Lift the engine sideways out of
the engine housing.

To replace engine housing - see

11.9.

Assembly is a reversal of the
disassembly sequence.

Note: Pay special attention to the
following points.

- Fit collar stud 4 and torque it
down to 30 Nm (22 Ibf.ft).

- Fit mounting screws 2, 3 and 5
and torque them down to 11 Nm
(8 Ibf.ft).

- Tighten down mounting screw 1 to
11 Nm (8 Ibf.ft).

- Push ignition lead into groove
and retainer on cover.

- Push the tank vent into the hole in
the cover.

- Remove the engine - see 4.4.

- Pull the impulse hose off the
nipple on the cylinder.

- Release the hose clamp on the
manifold. Pull the manifold off the
intake port.

STIHL 029, 039 31

Top:
Fitting clamping strap on
piston rings

Bottom:
1 = Piston pin
2 = Channel section on
clamping strap

Correct position of
piston rings

Top:
Inner contour of cylinder

Bottom:
Clamping strap 1127 893 2600

- Pull the engine pan off the
cylinder.

- Lift the crankshaft and pull the
piston out of the cylinder.

- Inspect the cylinder and replace
it if necessary.

Note: If a new cylinder has to be
installed, always fit the matching
piston. Replacement cylinders are
only supplied complete with piston
for this reason.

- Thoroughly clean all residue of
sealant from the cylinder and
engine pan mating faces.

- Lubricate piston and piston rings
with oil.

- Position the piston rings so that
the radii at the ring gap meet at
the fixing pin in the piston groove
when the rings are compressed.

Note: The clamping strap can only
be used with cylinders whose inner
contour is the same as that shown in
the illustration above.

- Use the clamping strap to com­press the piston rings around the
piston and check that the piston
rings are correctly positioned.

- Close the clamping strap and
compress it so that the lug engages
the square hole.

- Position the clamping strap so that
its channel sections line up with the
center of the piston pin.

STIHL 029, 039 32

Top:
Top:
Fitting the piston

Bottom:
1 = Long crankshaft stub
2 = Exhaust port

1 = Long crankshaft stub
2 = Tapped hole for bar

mounting stud

Straight faces on manifold and

intake port

Bottom:

Correct position of hose clamp

a = 8 mm (5/16")

- Apply a thin coating of sealant to
the outer diameters of the oil seals

- see 12.2.

- Position piston with clamping strap
in cylinder so that the channel
sections on the clamping strap rest
on the lands in the cylinder.

- Carefully push the piston into the
cylinder. Open the clamping and
take it away.

- Line up the crankshaft so that its
long stub is on the right - looking at
the exhaust port.

- Apply a thin bead of sealant to the
engine pan mating face - see 12.2.

Note: Follow manufacturer's
instructions for use of sealant.

- Fit the engine pan so that the seat
for the oil pump is at the same side
as the long crankshaft stub.

- Push the manifold on to the
intake port so that the straight faces
of the manifold and intake port are in
alignment.

- Fit the hose clamp on the manifold
so that its ends point up and the
screw head is on the left.

- Tighten the screw until the gap
between the two ends of the hose
clamp is about 8 mm (5/16").

- Assembly of all other parts is now a
reversal of the disassembly
sequence.

STIHL 029, 039 33

4.6 Piston

Top:

Top:
Removing snap ring

Bottom:
Assembly drift 1110 893 4700

Pushing out piston pin

Bottom:
Piston rings

1 = "N" marking on piston

head

Top:
Needle cage in small end

Bottom:
1 = Installing tool 5910 890 2210
2 = Sleeve

- Pull the piston out of the cylinder ­see 4.5.

- Use a scriber or similar tool to
ease the hookless snap rings
out of the grooves in the piston
bosses.

- Use the assembly drift to push
the piston pin out of the piston. If
the piston pin is stuck, tap the
end of the drift lightly with a
hammer if necessary.

Important: Hold the piston steady
during this process to ensure that no
jolts are transmitted to the con­necting rod. Remove the piston and
take the needle cage out of the
connecting rod.

- Inspect piston rings and replace if
necessary - see 4.7.

Note: Only special pistons may be
installed in low compressions saws
(i.e. "N"). The machine numbers of
low compression saws have the suffix
"N". In addition, the piston

head is marked with the letter "N", as
in the inside of the piston.

- Lubricate the needle cage with oil
and fit it in the small end.

- Fit a snap ring in one piston boss.

Note: Use special installing tool
5910 890 2210 to fit the snap ring.

STIHL 029, 039 34

p

Top:
Modified sleeve
a = 16 mm (11/16")
b = 8 mm (5/16")
c = 20 mm (25/32")

Bottom
1 = Snap ring (hookless)
2 = Magnet

Top:
1 = Flat on end of shank
2 = Pin

Bottom:
Pushing installing tool into sleeve as far
as sto

Top:
Slipping sleeve onto other end of
shank

Bottom:
Fitting snap ring in
piston boss

Owing to the special shape of the
piston it is necessary to modify the
sleeve of the installing tool as shown
in the illustration.

Use the installing tool as follows:

- Remove the sleeve from the tool.

- Attach the hookless snap ring to the
magnet so that the snap ring gap is
on the flat side of the tool's shank
(see illustration).

- Push the slotted diameter of the
sleeve over the magnet and snap
ring so that the inner pin points at
the flat face of the tool's shank.

- Stand the installing tool, sleeve
downward, on a flat surface
(wooden board) and press
vertically downwards until the
sleeve butts against the tool's
shoulder.

- Remove the sleeve and slip it
onto the other end of the shank.

Note: Pin must point toward flat
face of tool's shank.

- Apply the installing tool to the
piston boss, hold the piston
steady, center the tool shank
exactly and press home until the
snap ring slips into the groove.

STIHL 029, 039 35

tting pisto

g

4.7 Piston Rings

1 = Mark (arrow)
2 = Long crankshaft stub

Note: The snap ring must be fitted so
that the ring gap is on the piston's
vertical axis (it must point either up or
down).

Top:
Installing the piston pin

Bottom:
Insetting snap ring with installing
tool 5910 890 2210

Top:
Piston ring grooves

Bottom:
Fi

n rin

- Heat the piston on an electric
heating plate to approx. 60°C
(140°F) and slip it over the con­necting rod so that the mark (arrow)
on the piston head points towards
you - the long stub of the crankshaft
must be on the left.

- Push the assembly drift, small
diameter first, through the snap ring
already fitted, the piston bore and
the small end (needle cage). Line up
the piston.

- Fit the piston pin on the assembly
drift and slide it into the piston (the
piston pin slides home easily when
the piston is hot).

- Use the installing tool 5910 890

2210 to fit the snap ring in the
piston boss.

Note: The snap ring must be fitted
so that the ring gap is on the
piston's vertical axis (it must point
either up or down).

- Install the piston - see 4.5.

- Remove the piston from

the cylinder - see 4.5.

- Remove rings from piston.

- Use a piece of an old piston
ring to scrape the grooves
clean.

- Install the new piston rings in

the grooves so that the radii at
the ring gaps face upward.

- Install the piston - see 4.5.

STIHL 029, 039 36

g

ping

g

4.8 Crankshaft

Top:
1 = Crankshaft
2 = Connecting rod

Bottom:
Oil seals

Top:
Ball bearings

Bottom:
Closed side of ball bearin

1 = Sealing lip
2 = Clam

rin

- Pack space between sealing and
dust lips of oil seals with grease ­see 12.2.

- Apply thin coating of sealant, ­see 12.2, to outside diameters of oil
seals.

The crankshaft, connecting rod and
needle bearing are an inseparable
assembly. This means that the
crankshaft must always be replaced
as a complete unit in the event of
damage to any one of these parts.

When fitting a replacement crank­shaft, always install new ball
bearings and oil seals.

- Slide oil seals on to crankshaft
stubs so that the clamping ring
points outward (sealing lip also
points outward).

Assembly of other parts is a
reversal of the disassembly
sequence.

- Remove the piston - see 4.6.

- Pull both oil seals off the crank­shaft stubs.

- Pull both ball bearings off the
crankshaft stubs.

- Note that closed side of ball
bearings must face outward
when they are installed. Heat
new ball bearings to approx.
50°C (120°F) and push them on
to the crankshaft stubs as far as
stop.

STIHL 029, 039 37

5. IGNITION SYSTEM

Warning: Exercise extreme

caution when carrying out
maintenance and repair work on
the ignition system. The high
voltages which occur can cause
serious or even fatal accidents!

1 = Ignition module
2 = Flywheel

5.1 Repairing Component

Parts

5.1.1 Spark Plug

Troubleshooting on the ignition
system should always begin at the
spark plug.

In the event of starting difficulties, low
engine power, misfiring, etc., unscrew
the spark plug and check that it is the
approved type. Only the spark plugs
listed in the specifications may be
used. Other makes of spark plug are
unsuitable because they have long­reach electrodes.

Top:
Checking electrode gap with
feeler gauge

Bottom:
Resetting electrode gap with
Bosch spark plug gauge

STIHL 029 and 039 chain saws are
equipped with an electronic
(breakerless) magneto ignition
system which requires no outside
power source (battery or dynamo).

The system basically consists of an
ignition module and flywheel and is
easily accessible.

Sooted or carbonized spark plug:

- Use brass wire brush to clean the
spark plug and then blow it clear
with compressed air.

Note: Never use a steel wire
brush for this job.

Spark plug smeared with oil:

- Wash the insulator nose with a
grease solvent and blow it clear
with compressed air.

Electrode gap:

Electrode gap becomes wider as a
result of normal erosion.

- Check the electrode gap at
regular intervals with a feeler
gauge. It should be 0.5 mm
(0.02").

- Bend the ground electrode as
necessary.

Important: Always fit a new spark
plug if the electrodes are badly
eroded.

STIHL 029, 039 38

Checking the spark plug:

Accurate checking of the spark plug
is only possible with a special spark
plug tester.

A provisional check can be carried
out by fitting a clean spark plug in the
spark plug terminal and holding it
against ground. Set the Master
Control to the "RUN" position. There
should be a powerful sparkover at the
electrodes when you crank the
engine with the starter rope.

The appearance of the spark plug's insulator nose gives valuable information with regard to the effects of various
operating conditions:

Condition of insulator nose

Warning: Do not touch any live
parts - contact with high voltage
can cause serious or fatal
accidents.

Note: It is recommended that a
new spark plug be fitted in all
cases of doubt.

If there is no sparkover even
though the spark plug is in good
condition, first check the con­nections.

Note: Chafed insulation on the ignition
lead or short circuit wire will cause a
short-circuit to ground. In this case the
engine with either not start or only run
erratically.

Installing the spark plug:

- Clean the spark plug seat and
inspect the sealing ring to make
sure it is in good condition.

- Fit the spark plug and tighten it to
25 Nm (18.5 Ibf.ft).

Meaning

Normal:

Sooted:

Smeared with oil:

Overheated:

Grayish yellow to brown, dry

Velvet-like, dull black coating of
soot

Coating of damp oil carbon and
soot

Welding beads on insulator nose,
pitted electrodes

Engine in order; correct spark plug
(heat range as specified)

Mixture too rich, lack of air (dirty air
filter, choke shutter partly closed),
electrode gap too wide, wrong spark
plug (heat range too high)

Too much oil in fuel mix

Mixture too lean, spark plug loose,
wrong spark plug (heat range too
low)

STIHL 029, 039 39

)

5.1.2 Ignition Module 5.1.2.1 Ignition Timing 5.1.2.2 Removing and Installing

Top:
1 = Spark plug terminal
2 = Ignition lead retainer
3 = Groove

1 = High voltage output
2 = Connector tag

Ignition timing on the electronic
(breakerless) magneto ignition
system is fixed at 2.4 mm (0.095")
B.T.D.C. at 8,000 r.p.m. and is not
adjustable.

However, in view of the permis­sible tolerances in the electronic
circuit, it may vary between 2.0
and 2.8 mm (0.080" and 0.11 ")
B.T.D.C. at 8,000 r.p.m.

Bottom:
1 = Lead retainer
2 = Short circuit wire

The ignition module accommodates
all the components required to control
ignition timing. There are two
electrical connections on the coil
body:

1. the high voltage output

2. the connector tags for the short
circuit wires

Accurate testing of the ignition
module is only possible with
sophisticated test equipment. For
this reason it is only necessary to
carry out a spark test in the work­shop. A new ignition module must be
installed if no ignition spark is
obtained (after checking that wiring
and stop switch are in good
condition

.

Since there is no mechanical wear in
these systems, ignition timing cannot
get out of adjustment. However, an
internal fault in the circuit can alter the
switching point in such a way that a
spark test will still show the system to
be in order although timing is outside
the permissible tolerance. This will
impair engine starting and running
behavior.

- Remove handle housing - see

8.1.1.

- Pull terminal off the spark plug.

- Remove the ignition lead from
the retainer and groove on the
cover.

- Pull the short circuit wire off the
tag on the ignition module and
remove it from the lead retainer.

STIHL 029, 039 40

q

Top:
Ignition module mounting
screws

Bottom:
Pulling the unscrewed ignition lead
out of ignition module

Top:
Removing lead retainer

Bottom:
Setting gauge 1127 890 6400

Setting gauge fitted between
flywheel and ignition module

Remove the ignition module
mounting screws.

Pull the ignition module forward
and push back the grommet on
the high voltage output.

Unscrew the ignition lead from the
contact pin and pull it out of the
ignition module.

If necessary, ease the peg of the
lead retainer out of its seat and
remove the retainer.

Note: Before fitting the ignition lead,
pack the high voltage output with
STIHL multipurpose grease –
see 12.2.

Important: Do not use graphite
grease (Molykote) or silicone
insulating paste for this job.

- Push the grommet over the
ignition module's high voltage
output.

- Place the ignition module in
position, fit screws but do not
tighten down yet.

Important: Secure ground wire with
upper screw and fit a washer on the
lower screw.

- Slide the setting gauge between
the arms of the ignition module and
the flywheel magnets.

- Press the ignition module against
the flywheel and tighten down the
mounting screws to a torque of

4.8 Nm (3.5 Ibf.ft).

Important: Tighten the upper
screw first.

- Remove the setting gauge and
use a feeler gauge to check the air
gap. It should be 0.15 - 0.3 mm
(0.006 - 0.012").

Assembly of the remaining parts is
now a reversal of the disassembly

uence.

se

STIHL 029, 039 41

5.1.3 Spark Plug Terminal

Top:
Removing dust seal

Bottom:
Pulling leg spring out of spark
plug terminal

Fitting dust seal

- Unhook the leg spring from the
ignition lead and slip the spark
plug terminal and dust seal off
the lead.

Top:
Fitting the leg spring

Bottom:
Correct position of leg spring in spark
plug terminal

- Remove handle housing - see

8.1.1.

- Pull terminal off the spark plug and
remove the ignition lead from the
retainer.

- Pull the dust seal off the spark
plug terminal and push it down
the ignition lead.

- Use a suitable pair of pliers to

grip the leg spring and pull it out
of the spark plug terminal.

- Slip the dust seal over the
ignition lead.

- Coat end of the ignition lead
with oil (about 20 mm/3/4").

- Fit spark plug terminal over the
ignition lead.

- Use suitable pliers to grip the end of
the ignition lead inside the spark
plug terminal and pull it out.

Pinch the hook of the leg spring into
the center of the lead, i.e. about 10
mm (3/8") from the end of the lead.

- Pull the lead back into the

terminal so that the leg spring
locates properly inside it (see
illustration).

- Fit the dust seal over the spark
plug terminal.

- Fit the terminal on the spark plug.
Push the ignition lead into the
retainer and groove on the cover.

- Fit the handle housing - see 8.1.1.

STIHL 029, 039 42

g

5.1.4 I

Top:
Grommet

Bottom:
Pulling ignition lead out of
tank housing

nition Lead

Piercing center of ignition lead

5.1.5 Flywheel

Top:
Locking strip 0000 893 5902 in
cylinder

Bottom:
Fan housing mounting
screws

- Remove ignition module - see

5.1.2.2.

- Pull the grommet off the ignition
lead.

- Pull the ignition lead out of the
hole in the tank housing.

- Remove the spark plug terminal ­see 5.1.3.

- Cut new ignition lead to length
(see parts list or cut to same
length as old lead).

Reassembly is a reversal of the
disassembly sequence.

Note: Use a pointed tool (awl or
gimlet) to pierce the center of the
other end of the ignition lead which
screws into the module.

Note: Before fitting the ignition lead,
pack the high voltage output with
STIHL multipurpose grease –
see 12.2.

Important: Do not use graphite
grease (Molykote) or silicone
insulating paste for this job.

Removing the flywheel:

- Block piston with locking strip ­see 3.2.

- Take out the fan housing mount-

ing screws and remove the fan
housing.

STIHL 029, 039 43

Top:
Flywheel mounting nut

Bottom:
Removing the flywheel

Top:
Puller 1116 893 0800

Bottom:
Puller fitted in position

1 = Flywheel
2 = Magnet poles

- Inspect the condition of the
flywheel. If you find any damage
(e.g. cracks, broken fan blades),
fit a new flywheel.

- Rotate the flywheel so that the
magnet poles are opposite the
ignition module.

- Unscrew flywheel mounting nut
from the crankshaft.

- Pull the flywheel off the crank­shaft.

Note: If the flywheel cannot be
removed by hand, screw the puller
onto the crankshaft stub, tap the end
of the puller lightly with a hammer to
release the flywheel. Unscrew the
puller.

Installing the flywheel:

Important: Clean the stub of the

crankshaft and the flywheel hub
bore with a standard commercial,
solvent-based degreasant containing
no CFCs. Fit the flywheel and tighten
mounting nut to 27.5 Nm (20 Ibf.ft).

Assembly of the remaining parts is
now a reversal of the disassembly
sequence.

STIHL 029, 039 44

5.1.6 Short Circuit Wire/
Ground Wire

Top:
Ground wire fastening
screw

Bottom:
Withdrawing short circuit wire and
ground wire

Grommet

5.1.7 Contact Spring

Top:
Ground wire terminal

Bottom:
Removing contact spring

- Remove handle housing - see

8.1.1.

Remove the flywheel - see 5.1.5.

- Remove the ignition module

-see 5.1.2.2.

- Remove the ground wire

fastening screw from the
cylinder.

- Pull the short circuit and ground
wires out of the hole in the engine
housing.

- Pull the grommet off the short

circuit and ground wires.

Installation is a reversal of the
removal sequence.

- Remove the air filter - see 11.1.

- Remove the switch shaft - see

9.1.

- Pull the ground wire terminal off
the contact spring.

- Ease the contact spring out of its
seat in the handle housing.

Installation is a reversal of the
removal sequence.

STIHL 029, 039 45

p

6. REWIND STARTER

6.1 Routine

Maintenance

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 paraffin (kerosine) to the
rewind spring.

6.2 Rope Rotor/Pawl

Fan housing mounting
screws

Top:
Removing spring clip

Bottom:
Pulling rope rotor off the
starter post.

Carefully pull out the starter rope
several times and allow it to rewind
until its normal smooth action is
restored.

If clogged with dirt or pitch, the entire
starter mechanism, including the
rewind spring, must be removed and
disassembled. Take special care
when removing the spring.

Wash all parts in paraffin or white
spirit.

Lubricate the rewind spring and
starter post with STIHL special
lubricant, see 12.2, before instal­ling.

Removing rope rotor:

Troubleshooting chart - see 2.4.

The fan housing has to be re­moved for access to the starter
mechanism.

Relieving tension of rewind
spring:

- Pull out the starter rope to a
length of approx. 5 cm (2 - 3 in)
and hold the rope rotor steady.

- Take two turns of the rope off the
rotor.

- Pull out the starter grip and let go
of the rope rotor.

Note: The rope rotor will spin back
and relieve the tension of the rewind
spring. The rewind spring will not be
under tension if the starter rope is
broken.

- Remove the starter rope from the
rotor.

- Use screwdriver or suitable pliers
to carefully remove the spring clip
from the starter post.

- Take the washer and rope rotor
and with pawl off the starter post.

- If necessary, remove the pawl
from the rope rotor.

- Replace the worn or broken
starter ro

e - see 6.3.

STIHL 029, 039 46

6.3 Replacing the
Starter Rope

Top:

1 = Spring clip
2 = Pawl
3 = Washer

Correct position of starter rope in
rope rotor

Bottom:
Starter rope secured in rope rotor with
knot

Top:
1 = Special knot
2 = Rope guide bush

Bottom:
Special knots used

Installing the rope rotor:

- Lubricate guide peg on pawl with
graphite grease, see 12.2, and then
fit the pawl.

- Coat the bore in the rope rotor with
STIHL special lubricant - see 12.2.
Fit the rotor on the starter post so
that the inner spring loop slides into
the lug on the rotor.

Note: Check that the spring loop
has engaged by turning the rope
rotor slightly and letting it go - it
must spin back.

- Fit the washer and install the
spring clip in the starter post
groove.

Note: Make sure the spring clip
engages the pawl guide peg and
points it in the clockwise direction.

- The spring clip must be treated
very carefully. If it is bent or
twisted during disassembly or
assembly, the rewind starter
might malfunction.

- Remove the rope rotor - see 6.2.

- Remove the remaining rope from
the rope rotor. Thread end of new
rope (3.5 mm (0.14") dia., 960
mm (37.8") long) through the rotor
and secure it with a simple
overhand knot.

- Pull the rope back into the rotor
so that it locates in the recess.

- Thread the other end of the rope
through the guide bush from
inside the fan housing and through
the bottom of the starter grip.
Secure with one of the special
knots shown.

- Install the rope rotor - see 6.2.

- Tension the rewind spring –
see 6.5.

STIHL 029, 039 47

p

y

6.4 Replacing the

Rewind Spring

Top:
Position of anchor loop a =
20 mm (3/4")

Bottom:
Fitting rewind spring with aid of wooden

block 1108 893 4800

assembl

6.5 Tensioning the

Rewind Spring

Top:
Tensio ning the rewi nd spri ng

Bottom:
Straightening twisted ropeRewind spring in position

- Remove the rope rotor, see 6.2.
Take out the spring housing. Use
pliers to remove any remaining
pieces of spring from the fan
housing.

- The rewind spring is supplied
ready for installation with the
spring housing. It should be
lubricated with a few drops of
STIHL special lubricant before
installation.

- Position the rewind spring with
spring housing (bottom plate must
face up) in the fan housing.
Engage the anchor loop over the
lug in the starter cover.

Caution: The rewind spring can
pop out and uncoil during install­ation.

- If the rewind spring has popped

out, refit it as follows:

- Position anchor loop about 20
mm (3/4") from the edge of the
spring housing.

- Refit the rewind spring in the
spring housing in the counter­clockwise direction, starting
outside and working inwards.

Note: The wooden assembly block
can be placed over the spring
housing to simplify refitting.

- Make a loop in the starter rope.

- Grip the rope close to the rotor
and use it to turn the rope rotor
six full turns clockwise.

- Hold the rope rotor steady.

- Pull out the rope with the starter
grip and straighten it out.

- Install the ro

e rotor - see 6.2.

STIHL 029, 039 48

6.6 Replacing the Starter
Rope Guide Bush

Top:
Installing tool 0000 890 2201

Bottom:

Rope guide bushGrip on fan housing

Flaring the new rope
guide bush

- Hold the starter grip firmly to
keep the rope tensioned.

- Let go of the rope rotor and
slowly release the starter grip.

Note: The rewind spring is correctly
tensioned when the starter grip sits
firmly in the rope guide bush 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, pull the rope out, hold the rope
rotor steady and take off one turn of
the rope.

Do not overtension the rewind
spring as this will cause it to
break.

- Refit the fan housing.

The wear on the guide bush is
accelerated by the starter rope being
pulled sideways. The wall of the guide
bush eventually wears through,
becomes loose and has to be
replaced.

- Remove the fan housing.

- Remove the rope rotor, see 6.2,
take off the starter grip and pull out
the rope.

- Use a screwdriver to pry the old
bush out of the fan housing.

Installing the new rope bush:

- Place the new bush in its seat in
the fan housing.

- Insert the screw spindle of the
installing tool through the bush
from inside the housing.

- Fit the thrust sleeve, tapered end
first, and the hexagon nut.

- Tighten down the hexagon nut
until the bush is firmly seated.

Note: The installing tool flares the lower
end of the rope bush.

- Refit the starter rope and starter grip.

- Install the rope rotor - see 6.2.

- Tension the rewind spring - see 6.5.

- Fit the fan housing.

STIHL 029, 039 49

7. AV HANDLE SYSTEM

7.1 Repair

Top:
Removing annular buffer from front
handle

Bottom:
Removing lower annular buffer from
engine housing

Top:
Fitting buffer in front handle
1 = Groove

Bottom:
Fitting buffer in engine housing
1 = Groove

Top:
Removi ng plug

Bottom:
Fitting buffer in engine housing
1 = Groove

Rubber anti-vibration buffers are
installed between the handle housing
and engine housing. Damaged
rubber buffers (annular buffers) must
always be replaced.

- Remove the front handle –
see 8.1.

- Remove both annular buffers

from the front handle.

- Push the lower annular buffer

out of the engine housing.

- Push the annular buffer into the front
handle (from inside) until its groove
engages over the housing rib.

- Push the lower annular buffer into
the engine housing until its groove
engages over the housing rib.

Note: To replace the upper annular
buffer it is necessary to remove the
exhaust muffler and handle housing,
see 4.1 and 8.1.1.

- Pry the plug out of the upper
annular buffer. Remove upper
annular buffer from the engine
housing.

- Push the annular buffer into the

engine housing from outside until its
annular groove engages over the
edge of the housing.

Assembly is now a reversal of the
disassembly sequence.

STIHL 029, 039 50

g

8. HANDLE HOUSING

8.1 Front Handle

Top:
Lower mounting screws on front
handle

Bottom:
Plu

s

Top:
Front ha ndle mo unting
screws

Bottom:
Removi ng the front handle

8.1.1 Removing and Installing

Handle Housing

Top:
1 = Washer
2 = Sleeve

Bottom:
Withdrawing short circuit wire

- Take the lower mounting screws
out of the front handle.

- Remove the plugs from the annular
buffers on the front handle.

- Take out the front handle mounting
screws.

- Pull the front handle down and off
the handle housing, and then take
it away to the rear.

Assemble in the reverse sequence.

- Remove the front handle –
see 8.1.

- Remove the carburetor –
see 11.2.

- Slip the washer off the mounting
studs and take the sleeve out of
the manifold.

- Pull the short circuit wire's con­nector sleeve out of the switch
shaft.

STIHL 029, 039 51

Top:
Ground wire

Bottom:
Plug

Top:
Removing annular buffer

Bottom:
Removi ng handl e housi ng and
pushing out manifold at same time

Top:
Removing grommet

Bottom:
Removing the impulse
hose

- Pull the ground wire off the
contact spring.

- Ease the plug out of the annular
buffer on the hand guard.

- Push the annular buffer out of the
engine housing.

- Pull the handle housing slightly
forward and push the manifold
through the handle housing
opening at the same time.

- Ease the grommet for the ground
and short circuit wires out of the
handle housing.

- Remove the impulse hose from
the handle housing.

- Remove the handle housing and
pull the ground and short circuit
wires out of the bore at the same
time.

Assembly is a reversal of the
disassembly sequence.

STIHL 029, 039 52

Top:

1 = Bore for impulse hose

2 = Grommet for ground and short circuit

wires
3 = Impulse hose
4 = Fuel hose

Bottom:
String around manifold

Top:
Pulling manifold into handle
housing intake openi ng

Bottom:
Pulling impulse hose into position

Top:
Annular groove

Bottom:
Correct position of ground and short circuit
wires

Note: Pay special attention to the
following points.

- Place the handle housing in posi-

tion and thread the ground and short
circuit wires through the bore. Fit the
grommet in the bore.

- Position impulse hose in bore and

pass the fuel hose through the
lower slot.

- Wind a piece of string (about 15
cm / 6" long) around the back of
the manifold flange and pass the
ends through the intake opening.

- Press the intake opening of the
handle housing against the mani­fold and pull the ends of the string
outward at the same time. The
manifold flange is pulled through
the handle housing intake opening
without being damaged.

- Pull the impulse hose outward is
until its bead is in front of the
housing.

- Push the annular buffer into the
engine housing until its groove
engages the housing rib.

- Position the ground and short
circuit wires correctly in the
handle housing (see illustration)
and push them into their retainers.

STIHL 029, 039 53

9. MASTER CONTROL

9.1 Switch Shaft

Positions of Master
Control lever:
1 = STOP
2 = RUN
3 = START (warm start)
4 = CHOKE (cold start)

The main part of the Master Control
is the switch shaft with an integrally
molded multi-function operating
lever, a molded seat for the contact
spring and connector sleeve and
three levers.

Top:
Removing connector sleeve
1 = Seat on switch shaft

Bottom:
Detaching the switch
shaft

Top:
Withdrawing the switch shaft

Bottom:
Holding the contact spring up

The thumb-operated Master
Control lever moves the switch
shaft to select the required
function.

The following positions can be
selected with the Master Control
lever (from the top down):

- STOP (short circuit
contact closed,
ignition interrupted)

- RUN (normal operating
position)

- START (warm start ­starting throttle/
choke shutter open)

- CHOKE (cold start ­starting throttle/
choke shutter closed)

- Remove the carburetor box cover ­see 11.1.

- Set the Master Control to "CHOKE".

- Take the short circuit wire out of its
seat on the switch shaft.

- Pull the connector sleeve of the
short circuit wire out of the switch
shaft.

- Lever the switch shaft out of
its pivot mount.

- Pull the switch shaft out of
the bore.

Installation is a reversal of the
removal sequence.

Note: The contact spring must be
held up while installing the switch
shaft.

STIHL 029, 039 54

9.2 Interlock Lever/

Throttle Trigger

Top:
Withdrawing interlock lever

Bottom:
Disconnecting throttle rod
from throttle trigger.

Top:
1 = Cylindrical pin
2 = Torsion spring
3 = Throttle trigger

Bottom:
1 = Torsion spring
2 = Throttle lever

Top:
1 = Interlock lever
2 = Throttle trigger
3 = Master Control lever

Bottom:
Fitting handle molding

- Remove the carburetor box cover.

- Move Master Control to cold
start position (CHOKE).

- Take out the handle molding
fastening screw. Lift away the
handle molding.

- Take the interlock lever out of its
seat.

- Move Master Control lever to
"RUN" position.

- Disconnect the throttle rod from
the trigger.

- Use a 4 mm (5/32") drift to drive
out the cylindrical pin. Remove
the throttle trigger and torsion
spring.

- Position the torsion spring on the
throttle trigger -long leg of spring
must face upward.

- Fit the throttle trigger so that the
seat for the throttle rod points up
ward. Push the cylindrical pin into
position.

- Push the interlock lever into the
slots.

Note: The torsion spring must be
under the interlock lever and engage
the notch.

- Press the interlock lever down­ward. Push the throttle trigger
upward and move the Master
Control lever to the "CHOKE"
position.

- Fit the handle molding so that it
engages behind the lugs as
shown in the illustration. Secure
with screw.

STIHL 029, 039 55

10. CHAIN LUBRICATION

10.1 Suction Hose/Pickup Body

Top:
Removing suction hose from oil
pump nipple

Bottom:
Pulling out the suction hose

Top:
Pulling out suction hose with
pickup body

Bottom:
Pulling pickup body out of hose

Top:
Removing the strainer

Bottom:
1 = Hose
2 = Connector
3 = Strainer

Impurities gradually clog the fine
pores of the filter with tiny particles of
dirt. This prevents the oil pump from
supplying sufficient oil to the bar and
chain. In the event of problems with
the oil supply, first check the oil tank
and the pickup body.
Clean the oil tank if necessary.

- Remove the front handle –
see 8.1.

- Remove the clutch - see 3.2.

- Drain the oil tank.

- Push the suction hose off the
nipple on the oil pump.

- Pull the suction hose out of the
engine housing.

- Pull the suction hose with pickup
body out of the housing.

- Pull the pickup body out of the
hose.

- Use side cutters or similar tool to
remove the strainer from the
connector.

- Wash the strainer and pickup body
in white spirit and, if possible, blow
out with compressed air.

Important: Always replace a damaged
pickup body.

STIHL 029, 039 56

Top:
Oil filler cap

Bottom:
Pushing bead of suction
hose into position

10.2 Vent Valve

Top:
Vent valve

Bottom:
Installed position of valve a =
approx. 1 mm (3/64")

10.3 Removing and Installing

the Oil Pump

Top:
Removing the worm

Bottom:
Removing suction hose from oil
pump nipple

- Remove the oil filler cap and the
cap retainer. Flush out the oil tank.

Assembly is a reversal of the
disassembly sequence.

Note: Coat the bead of the suction
hose with oil to simplify fitting.

A valve is installed in the tank wall to
keep internal tank pressure equal to
atmospheric pressure.

- Drain the oil tank.

- Use a 7 mm (9/32") dia. drift to
carefully drive the vent valve into
the engine housing and then
remove it from the oil tank.

- Carefully press in the new valve
until it is about 1 mm (3/64") below
the face of the housing.

- Remove the clutch - see 3.2.

- Pull the worm and drive spring off
the crankshaft stub.

- Take the spring off the worm.

- Push the suction hose off the
nipple on the oil pump.

STIHL 029, 039 57

10.4 Servicing the

Oil Pump

1 = Pump piston
2 = Washer

3 = Helical spring
Top:
Removing the oil pump
1 = Elbow connector

Bottom:
O-ring

Top:
1 = Assembly sleeve 1122 893 4600
2 = Press sleeve 1127 893 2400

Bottom:
Press sleeve in position

4 = Washer

5 = O-ring

6 = Elbow connector

7 = Spring pin

8 = O-ring

9 = Control bolt

- Take out the oil pump mounting
screws.

- Push the oil pump to one side and
ease the elbow connector off the
nipple.

- Remove the oil pump.

- Take the O-ring off the nipple and
fit a new one.

- Place the pump in position and
line it up.

- Slip the assembly sleeve over the
crankshaft stub.

- Fit the mounting screws by hand.

- Place the press sleeve in position.
Tap the end of the press sleeve
lightly to seat the pump housing.

- Tighten screws to 4.0 Nm (3 Ibf.ft).

- Fit the worm.

- Install the clutch - see 3.3.

Always check the suction hose and
pickup body before disassembling the
oil pump.

- Remove the oil pump - see 10.3.

- Swing the elbow connector to one
side and pull it out of the housing.

- Remove the O-ring from the elbow
connector.

- Use a 2 mm (5/64") dia. drift to drive
out the spring pin. Pull the control
bolt out of the housing and remove
the O-rings.

- Take out the pump piston with helical
spring and washers.

- Wash all parts in white spirit. Inspect
the parts for damage and replace as
necessary.

Assembly is a reversal of the
disassembly sequence.

Note: Always install new O-rings. Coat
the pump piston and worm with grease,

- see 12.2, before installing.

STIHL 029, 039 58

11. FUEL SYSTEM

11.1 Air Filter

Top:
Twist lock on carburetor box cover

Master Control in
"CHOKE" position

Bottom:
1 = Prefilter
2 = Slotted nuts

Separating two halves of air filter

The air filter's function is to remove any
dust and dirt sucked in with the
combustion air and thus help reduce
wear on engine components to a
minimum.

Dirty and clogged air filters reduce
engine power, increase fuel con­sumption and make starting more
difficult.

The air filter should always be
cleaned when engine power begins
to drop off.

Before removing the filter, close the
choke shutter to prevent dirt falling
into the carburetor - press down the
interlock lever and move Master
Control down to cold start position
(CHOKE).

- Turn twist lock on carburetor box
cover one quarter turn counter­clockwise and take away the cover.

- Clean away any loose dirt from
around the filter.

- Push the prefilter up a little or take
it out of the recesses in the handle
housing.

- Unscrew the slotted nuts.

- Pull the air filter off the studs.

- Separate the two halves of the
filter.

- Wash both parts of the filter in a
fresh, non-flammable cleaning
solution (e.g. warm soapy water)
and, if possible, blow clear with
compressed air. Encrusted dirt
should be softened by immersing
the filter in the cleaning solution.

Important: Do not clean flocked air
filters with compressed air, brushes
or rags.

Note: If the filter is damaged,
replace it immediately.

Installation is a reversal of the
removal sequence.

STIHL 029, 039 59

11.2 Removing and Installing

the Carburetor

Top:
Flanged lock nuts

Bottom:
Detaching throttle rod

Top:
Detaching throttle rod

Bottom:
Removing grommet for adjusting screws

Removing the carburetor
1 = Fuel hose

- Remove the grommet from the

adjusting screws and pull it out of
the handle housing.

- Pull the carburetor off the studs

and pry the fuel hose off the
elbow connector at the same time.

The all-position diaphragm carburetor
consists of a fuel pump and the actual
carburetor. Although the fuel pump
shares a common housing with the
carburetor, it operates as a complete­ly separate and independent unit.

Troubleshooting chart - see 2.6.

- Remove the air filter - see 11.1.

Note: For removal of carburetor on
machines with automatic choke ­see 11.6.8.

- Unscrew the flanged lock nuts
from the mounting studs.

- Disconnect the throttle rod from
the throttle trigger.

- Disconnect the throttle rod from
the throttle shaft.

Installation is a reversal of the
removal sequence.

Note: Check that sleeve (in manifold)
and washer are in place before fitting
the carburetor in position. Push the
fuel hose on to the elbow connector
on left side of carburetor. After fitting,
check that elbow connector on
underside of carburetor is properly
engaged in impulse hose. Fit new
flanged lock nuts and torque them
down to 3.2 Nm (2.4 Ibf.ft).

STIHL 029, 039 60

r

11.3 Leakage Testing the

Carburetor

Top:
Nipple 0000 855 9200
fitted in fuel line
1110 141 8600

Bottom:
Fuel line on elbow
connector

Pressure testing carburetor with
carburetor/crankcase
tester 1106 850 2905

11.4 Servicing the

Carbureto

Fastening screw on fuel
pump end cover

The carburetor can be tested for
leaks with the carburetor and
crankcase tester.

- Remove the carburetor, - see 11.2.

- Connect tester's pressure hose to
elbow connector on side of car­buretor. Note that a separate nipple
and a length of fuel line are required
to make this connection.

- Close the vent screw on the rubber
bulb and pump air into the carburetor
until the pressure gauge shows a
reading of approx. 0.4 bar (5.8 psi).

If this pressure remains constant, the
carburetor is airtight. However, if it
drops, there are two possible causes:

1. The inlet needle is not sealing

(foreign matter in valve seat or
sealing cone of inlet needle is
damaged or inlet control lever
sticking).

2. The metering diaphragm is

damaged.

In either case the carburetor must
be removed and serviced.

Zama and Walbro carburetors of
almost identical construction are
installed in these machines. The
servicing procedures for the Zama
carburetor are described below.
Differences in individual parts are
described separately.

It is advisable to check the service­ability of the fuel pump whenever the
carburetor is removed for repair.

- Remove the carburetor –
see 11.2.

- Unscrew the fuel pump end

cover and take it off.

STIHL 029, 039 61

Top:
Fuel pump end cover with
gasket

Bottom:
Pump diaphragm on
carburetor body

Top:
Fuel strainer in carburetor body

Bottom:
Fastening screws of metering
chamber end cover

Top:
Metering diaphragm with gasket
on end cover

Bottom:
Separating gasket and diaphragm

- Remove the gasket and pump
diaphragm.

Note: The diaphragm and gasket
often stick to the cover or carburetor
body. If this is the case, take
particular care when separating
them.

- If the fuel strainer in the pump
side of the carburetor body is
dirty, use a scriber to remove it
and then clean it.

Important: If the fuel strainer is
damaged, fit a new one.

In such a case the fuel pickup body
should also be inspected and replaced
if necessary - see 11.8.

- To disassemble the carburetor,
take out the screws of the
metering chamber end cover and
lift away the cover.

- Remove the metering diaphragm
and gasket from the carburetor
body or the cover.

- Carefully separate the diaphragm
and gasket.

Note: The diaphragms are the most
delicate parts of the carburetor. They
are subjected to continuous alternating
stresses and the material eventually
shows signs of fatigue, i.e. the
diaphragms distort and swell. Check
and replace if necessary.

STIHL 029, 039 62

Top:
Round head screw on control lever
spindle (Zama)

Bottom:
1 = Round head screw
2 = Inlet control lever
3 = Spindle
4 = Helical spring
5 = Inlet needle

Top:
Damaged inlet needle

Bottom:
Pressing out valve jet (Zama)

Top:
Pressing out valve jet (Walbro)

Bottom:
Carburetor adjusting screws

- The inlet needle valve is located in
a recess in the metering dia­phragm chamber. Remove the
round head screw or collar screw.

- Remove the inlet control lever
with spindle, helical spring and
inlet needle.

Note: If there is an annular inden­tation on the sealing cone of the inlet
needle, it will be necessary to replace
the inlet needle because it will no
longer seal properly. This is indicated
by constant flooding of the carburetor
even though the needle is clean.

- Use a 5 mm (approx. 3/16") dia.
drift to press the valve jet out of its
seat in the direction of the venturi
and wash it in white spirit

.

Note: On Walbro carburetor, use a
4 mm (approx. 5/32") dia. drift to
press the valve jet out of its seat.

- Remove the carburetor adjusting
screws.

STIHL 029, 039 63

Top:
Sealing plate (Zama)

Bottom:
Sealing plug (Walbro)

Removing the fixed jet
1 = Retaining ring
2 = Fixed jet
3 = O-ring

Correct position of inlet
control lever

- Remove the sealing plate or plug
from of the metering chamber.

Caution: The sealing plate or plug is
destroyed during removal. It should,
therefore, only be removed if a
replacement is available.

- The Walbro carburetor is equipped
with a fixed jet. To remove, use a
suitable tool to ease the retaining
ring out of its seat and then take
out the fixed jet and O-ring.

- Wash the carburetor body and all
serviceable parts in fresh white
spirit and blow clear with com­pressed air, paying special atten­tion to the bores and ports.

- To install the fixed jet, fit a new
O-ring in the bore for the fixed jet.
Press home the fixed jet (flat side
up) as far as stop and secure in
position with the retaining ring.

- When fitting the valve jet, make
sure it is exactly vertical in the
bore. Press it home until it is
flush with the bottom of the
metering chamber.

- Fit the inlet needle and the helical
spring in their respective bores.
Insert spindle in the inlet control
lever, engage clevis in annular
groove on the head of the inlet
needle and tighten down the round
head screw. Make sure that the
helical spring locates on the control
lever's nipple.

- Check easy action of the inlet
control lever.

Important: The top of the inlet control
lever must be level with the bottom of
the metering chamber. If necessary,
use suitable pliers to carefully bend the
lever.

- After fitting new sealing plate or
plug, fill gap between carburetor
body and plate or plug with Loctite –
see 12.2.

STIHL 029, 039 64

Top:
Top:
Locating pegs on body

Bottom:
Locating pegs on cover

Elbow connectors

Bottom:

Throttle shutter

fastening screw

Top:
E-clip

Bottom:
Withdrawing throttle shaft

- Fit the gasket, metering dia­phragm and end cover. The
metering diaphragm and gasket
are held in position by the
integrally cast pegs on the
carburetor body.

- Insert the fuel strainer at the
pump side. Fit the pump dia­phragm, gasket and end cover
and tighten down securely. The
pump diaphragm and gasket
are held in position by the
integrally cast pegs on the end
cover.

Note: Fit the end cover so that the
two elbow connectors are pointing
in the same direction.

- Refit the carburetor adjusting
screws.

- Carry out leakage test before
installing the carburetor –
see 11.3.

Removing the throttle shaft:

Note: For machines with automatic

- see 11.6.10.

choke

- Unscrew the throttle shutter
fastening screw.

- Use suitable pliers to pull the
throttle shutter out of the throttle
shaft.

- Pry the E-clip off the end of the
throttle shaft.

- Withdraw the throttle shaft from
the carburetor.

- Remove the torsion spring.

STIHL 029, 039 65

Top:
Correct position of torsion spring
(Zama)

Bottom:
Correct position of torsion spring
(Walbro)

Top:
Fitting throttle shutter

Bottom:
Choke shutter fastening
screw

Top:
Withdrawing choke shaft

Bottom:
Removi ng the torsion spring

- After fitting the throttle shaft,
check that the torsion spring is
correctly positioned.

- Fit the throttle shutter, round
notch first, with the small bore
pointing to the throttle lever.

- Coat the fastening screw with
Loctite, - see 12.2, and tighten
down firmly.

Removing choke shaft:

Note: For machines with automatic

choke - see 11.6.10.

- Unscrew choke shutter fastening
screw. Remove the choke shutter.

- Pry the E-clip off the end of the
choke shaft and withdraw the
shaft from the carburetor.

- Remove the torsion spring.

STIHL 029, 039 66

11.5 Carburetor Adjustment

Top:

Fitting choke shutter (Zama)
Top:
Correct position of torsion spring
(Zama)

Bottom:
Correct position of torsion spring
(Walbro)

1 = Large bore

2 = Small bore

Bottom:

Fitting choke shutter (Walbro)

1 = Round notch

2 = Indentation

1 = High speed adjusting screw
2 = Low speed adjusting screw
3 = Idle speed adjusting screw

- After fitting the choke shaft,
check that the torsion spring is
correctly positioned.

- Position choke shutter of Zama
carburetor so that the large bore
points toward the metering end
cover and the small bore toward
the lever on the choke shaft.

Note: Fit the choke shutter of Walbro
carburetor so that the round notch
points toward the metering end cover
and the indentations face inward.

- Coat the fastening screw with
Loctite, - see 12.2, and tighten
down firmly.

- Install the carburetor - see 11.2.

The carburetor has a standard
setting when it leaves the factory.

This is the optimum setting of the
high speed adjusting screw for the
barometric pressure and climatic
conditions at the factory (300 m/1000
ft above sea level). It ensures
maximum engine performance, fuel
efficiency and the highest possible
reliability.

Standard setting:

H = High speed adjusting screw

backed off 1 full turn

L = Low speed adjusting screw

backed off 1 full turn

If the carburetor has to be adjusted
from scratch, first carry out the
standard setting to obtain a starting
point for fine tuning.

If no tachometer is available, do not
turn the high speed adjusting screw
beyond the standard setting to make
the mixture leaner.

STIHL 029, 039 67

If the saw is used at high altitudes
(mountains) or near sea level:

A slight correction may be necessary.

For corrections to high speed adjusting
screw (H):

Use a tachometer - do not exceed
maximum permissible engine speed.

Engine can be damaged by lack of
lubricant and overheating.

Maximum engine speed with bar and
properly tensioned chain: 13,000 r.p.m.

- Check chain tension

- Check air filter and clean
if necessary

- Adjust idle speed correctly
(chain must not rotate)

- Start the saw ­warm up the engine

Turn high speed adjusting
screw (H) and low speed adjusting
screw (L) clockwise for leaner
mixture at high altitudes or counter­clockwise for richer mixture at sea level.

Corrections to high speed adjusting
screw:
The setting of the high speed adjusting
screw (H) affects the maximum off-load
engine speed. If the setting is too lean,
the maximum permissible engine speed
will be exceeded and increase the risk
of engine damage.

Adjusting engine idle speed:
A correction at the low speed (L)
usually necessitates a change in the
setting of the idle speed adjusting screw

(LA).

Engine stops while idling

Turn idle speed adjusting screw (LA)
clockwise until the chain begins to
run - then turn it back one quarter turn.

Chain runs while engine is idling

Turn the idle speed adjusting screw
(LA) counterclockwise until the chain
stops running - and then turn about
another quarter turn in the same
direction.

Erratic idling behavior, poor
acceleration Idle setting too lean.

Turn the low speed adjusting screw
(L) counterclockwise until the
engine runs and accelerates
smoothly.

Exhaust smokes at idle speed

Idle setting too rich. Turn the low
speed adjusting screw (L) clockwise
until the engine speed drops - and
then turn it back one quarter turn ­and check that the engine
accelerates smoothly when you open
the throttle.

Turn screws very slowly and
carefully - even slight adjustment
produce a noticeable change in
engine running behavior.

STIHL 029, 039 68

11.6. Automatic Choke

11.6.1 Description of Operation

Schematic
1 = Control valve
2 = Bellows
3 = Choke shutter
4 = Sintered polymer and foam filter
A = Variable cross section

The bellows are located in the
handle housing. The period for
which the belows open the choke
shutter depends on cylinder tem­perature. It varies between 3.5
seconds on a cold engine to approx.

0.1 seconds on a hot engine.

A system of levers connects the
choke shutter to the throttle shutter.
The throttle shutter is at an angle of
37 degrees to the carburetor
mounting flange just before the choke
shutter opens fully. The throttle
shutter returns to the idle position
when the choke shutter is fully open.

The automatic choke selects the
throttle and choke shutter positions
required for an optimum mixture.

It uses the cylinder temperature as a
parameter. Cross section "A" is
changed as a function of cylinder
temperature. This, in turn, alters the
time required to vent the bellows and
thus the opening speed of the choke
shutter.

The regular changes in pressure
which occur in the engine housing
are used to operate the automatic
choke.

These variations in pressure are fed
via a cutout in the engine housing
and through a port in the cylinder to
the control valve.

The control valve feeds the low
pressure waves at a predetermined
interval to the bellows, which
contract and thus open the choke
shutter.

Following a starting attempt, the
bellows are filled with air from the
carburetor box and returned to the
neutral position. The air required to
pressurize the bellows is drawn in
from the carburetor box via a foam
filter, a polymer sintered filter, a hose
and control valve.

The pressurizing process is ac­companied by a low whistling noise.
The polymer sintered filter and
foam filter are located in the area of
the handle housing.

A depression is maintained in the
bellows while the engine is running,
i.e. the bellows are contracted; the
choke shutter is open.

STIHL 029, 039 69

11.6.2 Troubleshooting Chart

Start machine
in normal way

Does

engine

run?

yes

Adjust carburetor -

see 11.5

Is

idle in

order?

no

no

Troubleshooting,

see 2.3 and 2.6

Bypass the control valve,

see 11.6.4

no

Is

idle in

order?

Replace hose/connector

to control valve

no

Is

idle in

order?

yes yes

Start

with automatic choke

Does

engine

run?

yes

Machine

is in order

no

Pressure-test bellows,

see 11.6.6

Check automatic choke,

see 11.6.3

STIHL 029, 039 70

11.6.3 Testing Automatic Choke

- Remove the air filter –
see 11.1.1 or 11.1.2.

- Pull the terminal off the spark
plug. Unscrew the spark plug.

- Close the choke by moving the
Master Control down to the cold
start position.

- Open the choke shutter slowly by
turning the right-hand end of the
shaft.

11.6.4 Leakage Testing

Engine Housing and
Control Valve

Air inlet hose on bellows

Control valve temperature
between +5°C (40°F) and +25°C
(77°F):

Choke shutter only begins to open
after several revolutions of crankshaft
and opens briefly to no more than 45
degrees when starter rope is fully
extended. It must not move to the fully
open position.

Control valve temperature
below -5°C (3°F):

Note: The throttle shutter must jump to

the idle position (almost closed) just
before the choke shutter is fully closed.
This is accompanied by a definite
clicking sound.

- Pull the starter rope slowly:
Depending on the temperature of
the control valve, you should
observe one of the following

functions:

Control valve temperature
above +35°C (95°F):

Choke shutter begins to open during
first revolution of crankshaft and
opens fully for brief moment after
second revolution of crankshaft.

Note: Pulling starter rope out about
40 cm (16") is equivalent to two
revolutions of crankshaft.

Choke shutter must not move
while the starter rope is pulled
out to its full length.

It is necessary to interrupt the
connection between the automatic
choke and atmosphere before testing
the engine housing and built-in control
valve for leaks.

The connection between the cylinder
and control valve is also tested for
leaks during the pressure and vacuum
tests. The vacuum test is used to check
the complete control valve since only
part of the valve is pressurized in the
pressure test.

- Remove the air filter - see 11.1.

- Pull the air inlet hose off the nipple
on the bellows.

STIHL 029, 039 71

A

11.6.5 Testing Control Valve

(removed from machine)

Top:
1 = Air inlet nipple
2 = Air outlet nipple

Top:
Fastening screw on filter box

Bottom:
Control valve bypassed

3 = Connector on cylinder

Bottom:
1 = Nipple 0000 855 9200 with

fuel line 1110 141 8600

2 =

ir inlet hose

Leakage test with vacuum pump
0000 850 3500

- Remove the fastening screw from
the filter box. Pull the filter box
with filters off the connector.

- For preparations - see 4.2.1.

- Bypass the control valve by
pushing the air inlet hose onto the
two nipples on the connector.

- For leakage test - see 4.2.2 and

4.2.3.

The control valve can be tested with
the vacuum pump that is used for
leakage-testing crankcases.

- Remove the control valve –
see 11.6.12.

- Push air inlet hose onto the air
outlet nipple and seal it, e.g. with
a scriber.

- Make connection between vacuum
pump and control valve - using fuel
line and nipple as adapter.

- Push tester's pressure hose onto
the nipple.

Note: Leave the cylinder connector
open.

- Pull out pump piston several times
until pressure gauge shows a
vacuum of 0.4 bar (5.8 psi).

Note: Vacuum must not drop more
than 0.2 bar (2.9 psi) within 5 sec.
If it does, the control valve is faulty.

Checking bellows air inlet
function

- Apply vacuum of 0.4 bar (5.8 psi).

- Open the air inlet hose.

Note: Vacuum must drop immediately
(approx. 0.5 sec.) to 0 bar (0 psi). If it
doesn't, the control valve is faulty.

STIHL 029, 039 72

r

11.6.6 Leakage Testing the

Bellows

Top:
Nipple 0000 855 9200
connected to fuel line
1110 141 8600

Bottom:
Fuel line connected to
nipple on bellows

Testing bellows for leaks with
carburetor/crankcase tester
1106 850 2905

11.6.7 Foam Filter/Polymer

Sintered Filte

Top:
Removing the foam
filter

Bottom:
Removing the polymer
sintered filter

The bellows can be checked for
leaks with carburetor and crank­case tester.

The following test is carried out with
the bellows removed from the
machine, but it can also be performed
with the bellows installed in the
machine. To do this, it is only
necessary to pull the air inlet hose off
the nipple.

- Use fuel line and nipple as
adapter to connect bellows to
gauge. Fit the fuel line on
bellows' nipple.

- Push tester's pressure hose onto
the nipple.

- Close the vent screw on the
rubber bulb and pump air into
the bellows until the pressure
gauge shows a reading of
approx. 0.1 bar (1.45 psi).

- If this pressure remains constant
for one minute, the bellows are
airtight. If not, install new bellows.

- Remove the air filter - see 11.1.

- Pull the foam filter out of the filter
box.

- Pull the polymer sintered filter out of
the filter box.

STIHL 029, 039 73

11.6.8 Removing and Installing

the Carburetor

Top:
Disconnecting throttle rod
from throttle shaft

Bottom:
Removing bellows from
choke lever

1 = Arm on choke lever
2 = Hook on throttle rod

11.6.9 Removing and Installing

Lever System on
Carburetor

Removing bell crank "G" and lever "H"

For removal of carburetor - see 11.2.

Only the additional operations are
described below.

- Remove the filter box together
with foam filter and polymer
sintered filter - see 11.6.7.

- Disconnect and remove the
throttle rod from the throttle
shaft.

- Carefully pry the bellows link off
the pin on the choke lever.

- Before attaching the throttle rod to
the throttle shaft, open the choke
shutter and use a suitable piece of
material (e.g. roll of paper) to hold
it in that position.

- Connect the throttle rod and
remove the material holding
the choke shutter.

Note: The hook on the throttle rod
must be in front of the arm on the
choke lever. Operate the throttle
lever to check whether the choke
shutter opens.

Removal:

- Remove the carburetor –
see 11.6.8.

- Carefully pry bell crank "G" and
lever "H" off the shafts.

- Remove the lever system from
the shafts.

- Take the torsion spring off the
throttle shaft.

Installation:

Note: Bell crank "G" and lever "H"

have to be pressed onto the shafts.
To do this, clamp the carburetor body
in position so that the pressure used
to install the levers is transmitted to
the carburetor body via a short part
of the shaft and the retaining ring. This
procedure ensures that the shaft is not
loaded beyond its buckling strength.

STIHL 029, 039 74

Top:
Levers "A" and "B" joined
by link "C"

Bottom:
D = Torsion spring
E = Throttle shaft

Top:
Fitting levers "A" and "B"

Bottom:
Rotating lever "B"

Top:
Fitting bell crank "G"

Bottom:
Pressing home bell crank "G"

- Carefully push the link "C" into
position to connect levers "A"
and "B".

- Fit the torsion spring on the throttle

shaft so that its bent end points
away from the carburetor.

- Push lever "A" on to the throttle
shaft and, at the same time, lever
"B" on to the choke shaft.

- Rotate lever "B" on choke shaft

counterclockwise as far as stop.

- Fit the bell crank "G" (with flat face
pointing to lever "B") over the choke
shaft so that the pin on lever "B" is
between the arms of bell crank "G".

- Rotate bell crank counterclock­wise until its right arm butts
against the pin on lever "B".

- With the bell crank in this posi­tion, carefully press it on to the
choke shaft.

Important: Take care not to bend the
shaft.

STIHL 029, 039 75

Top:
Backing off the
idle speed adjusting screw

Bottom:
Turning lever "A" and
opening choke shutter

Top:
Fitting lever "H"

Bottom:
Pressing lever "H" into position

Correct positions of choke
and throttle shutters

- Turn the idle speed screw "LA"
counterclockwise until the throttle
shaft is clear of the taper on the
idle speed screw.

- Open the choke shutter "I" and hold
it steady in that position.

- Swing lever "A" counterclockwise
as far as stop.

Checking installed positions of
levers:

- In the idle position the choke
shutter must be closed and the
throttle shutter at an angle of 37
degrees to the carburetor moun­ting face.

- Open the choke shutter by slowly
turning the right-hand end of the
choke shaft. The throttle shutter
must jump to the closed position
just before the choke shutter is fully
open. This is accompanied by a
definite clicking sound.

Important: The choke shutter must be
held open for the next two operations.

- Fit lever "H" on the throttle shaft
and rotate it counterclockwise
against the pin on lever "A".

- Press lever "H" on to the throttle
shaft.

STIHL 029, 039 76

/

11.6.10 Throttle Shaft

Choke Shaft

Top:
Attaching torsion spring
to lever "H"

Bottom:
Attaching torsion spring
to lever "A"

Correct positions of levers
"A" and "B"

Checking installed position of
torsion spring:

Top:
Withdrawing the choke shaft

Bottom:
1 = Torsion spring
2 = Choke lever
3 = Torsion spring
4 = Choke shaft

- Attach bent end of torsion spring
to lug on lever "H".

- Push the straight end of the
torsion spring between the car­buretor body and pin on lever "A"
and locate it behind the lever's
lug.

- Open throttle and choke shutters
simultaneously and hold them
steady: The torsion spring must
move levers "A" and "B" into the
positions shown in the illustration.

- Install the carburetor - see 11.6.8.

- Remove the lever system –
see 11.6.9.

- Remove the throttle shaft –
see 11.4.

- Remove the choke shutter –
see 11.4.

- Pry the E-clip off the choke
shaft and then withdraw the
choke shaft.

- Remove the torsion springs and
choke lever from the choke
shaft.

STIHL 029, 039 77

11.6.11 Hose/Connector

Top:
Hose on control valve

Bottom:
1 = Connector
2 = Hose

11.6.12 Control Valve

Top:
Cover mounting screws

Bottom:
Removing the clip

Top:
Removing the O-ring

Bottom:
1 = Hose
2 = Control valve

- Remove the handle housing –
see 8.1.1.

- Clean the cylinder and the area
around the control valve.

- Pull the hose off the nipple on the
control valve.

- Pull the connector out of the hose.

Install in the reverse sequence.

- Remove the handle housing –
see 8.1.1.

- Take out the cover mounting
screws and lift away the cover.

- Clean the cylinder and the area
around the control valve.

- Ease the clip away from both
sides of the cylinder.

- Remove the control valve from
the cylinder.

- Take the O-ring out of the hole in
the cylinder or off the control valve's
stub.

- Pull the hose off the control
valve's nipple.

- Test the control valve –
see 11.6.5.

STIHL 029, 039 78

11.6.13 Bellows

Top:
Withdrawing the stub

Bottom:
O-ring

Top:
Retainer

Bottom:
Installing the O-ring

1 =Collar
2 = Bellows
3 = Nipple

- Remove the carburetor –
see 11.6.8.

- Use a blunt tool to pry the
bellows out of the hole in the
handle housing.

- Pull the stub out of the control
valve.

- Remove the O-ring from the
stub.

- Take the retainer off the control
valve.

Installation is a reversal of the
removal sequence.

Note: Lubricate new O-ring with a
little oil and fit it in the hole in the
cylinder.

Position control valve against the
cylinder and push the stub into the
hole in the cylinder.

Check that clip is properly
positioned between cooling fins.

- Test the bellows - see 11.6.6.

- Push bellows home until the
collar locates behind the handle
housing.

- Line up the bellows so that its
nipple points upward.

- Install the carburetor - see 11.6.8.

STIHL 029, 039 79

11.7 Tank Vent

Removi ng tank vent

Top:
1 = Grub screw
2 = Vent hose

Bottom:
Correct positions of grub screws a =
approx. 18 mm (11 /16")

11.8 Fuel Pickup Body and

Fuel Hose

Assembly hook 5910 893 8800

Correct operation of the carburetor is
only possible if atmospheric pressure
and internal fuel tank pressure are
equal at all times. This is ensured by
the tank vent.

Important: In the event of trouble with
the carburetor or the fuel supply system,
always check and clean the tank vent.

- Remove the carburetor box cover –
see 11.1.

- Remove the vent from the nipple on
the fuel tank and take it out of its seat
in the cover.

- Use a 3 mm (1/8") dia. drift to push
the grub screws out of the hose.

- Wash all parts in fresh white spirit
and blow out with compressed air.

Installation of the tank vent is a
reversal of the removal sequence.

Note: Use a drift to position the
grub screws as shown in the
drawing.

Fit the tank vent on the nipple and
then push it into its seat in the cover.

The diaphragm pump draws fuel out of
the tank and into the carburetor via
the fuel hose. 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.

Important: In the event of trouble
with the fuel supply system, always
check the fuel tank and the pickup
body first. Clean the fuel tank if
necessary.

Cleaning the fuel tank:

- Unscrew the filler cap and drain the
tank.

- Pour a small amount of clean
gasoline into the tank.

- Close the tank and shake the saw
vigorously.

- Open the tank again and drain it.

STIHL 029, 039 80

11.9 Replacing the

Fuel Tank

1 = Spiked bumper

2 = Collar stud
Top:
Withdrawing the pickup body

Bottom:
Disconnecting pickup body

Top:
Removing suction hose

Bottom:
Correct position of hose flange

3 = Valve

4 = Bumper strip

5 = Rubber buffer

6 = Mounting screw

7 = Chain catcher

Removing and installing
the pickup body:

- Use the assembly hook to pull the
pickup body out through the fuel
tank filler opening.

Note: Do not over-stretch the
suction hose while pulling out the
pickup body.

- Pull the pickup body off the suction
hose and fit a new pickup body.

Installation is a reversal of the
removal sequence.

Removing the suction hose:

- Remove the handle housing –
see 8.1.1.

- Pull off the pickup body.

- Pry the suction hose out of the
tank. Remove the hose.

Installation is a reversal of the
removal sequence.

Coat the hose flange with a little oil
to simplify installation. The straight
side of the hose flange must locate
against the rib on the tank housing.

The fuel tank and engine housing are
one piece.

- Remove the engine - see 4.4.

- Remove the chain tensioner –
see 3.4 or 3.5.

- Remove the chain brake - see 3.3.1.

- Remove the fuel suction hose –
see 11.8.

- Remove the oil suction hose –
see 10.1.

- Remove the mounting screws from
the spiked bumper and take the
spiked bumper away.

- Remove the vent valve - see 10.2.

- Unscrew the collar stud - see 3.6.

- Pry the bumper strip out of its seat.

- Remove the rubber buffer - see 7.1.

- Remove the mounting screw from
the chain catcher and take away the
chain catcher.

STIHL 029, 039 81

Top:

Top:
O-ring

Bottom:
Removing the plug

Ignition module

Bottom:
1 = Ground wire
2 = Short circuit wire
3 = Ignition lead
4 = Grommet

Top:
Tank vent

Bottom:
Fitting annular buffer
1 = Groove

- Remove O-ring from nipple of oil
pump's elbow connector.

- Pry the plug out of the upper
annular buffer and then push
the buffer out of the housing.

- Remove the ignition module –
see 5.1.2.2.

- Pull the grommet off the ignition
lead.

- Pull the ignition lead, ground wire
and short circuit wire out of the
housing.

- Remove the tank vent from the
nipple on the tank housing.

Assembly is a reversal of the
disassembly sequence.

Note: After assembly, set the air
gap between the ignition module
and flywheel - see 5.1.2.2.

- Push the upper annular buffer into
the housing from outside so that
its groove engages over the edge
of the housing.

STIHL 029, 039 82

12. Special Servicing Tools and Aids

12.1 Special Servicing Tools

No.

1
2
3
4
5
6

7
8

9

10

11
12
13
14

15
16
17
18
19
20
21

22

23
24
25

26
27

28

29

Part Name

Locking strip
Clamping strap
Puller

- Jaws (No. 6)
Puller
Crimping tool

Assembly drift
Carburetor and
crankcase tester
Vacuum pump

Sealing plate

- Flange

- Sleeve (2x)
Test flange
Setting gauge

Socket, 13 mm
Socket, 19 mm
Torque wrench
Torque wrench
Screwdriver bit I-5x150
Assembly hook
Installing tool 10

Assembly hook

Installing tool
Assembly tube
T-handle screwdriver
QI-5x150
Stud puller M8
Assembly stand

Press sleeve

Assembly sleeve

Part No.

0000 893 5902
1127 893 2600
0000 890 4400
0000 893 3711
1116 893 0800
5910 890 8210

1110 893 4700
1106 850 2905

0000 850 3500

0000 855 8106

1123 855 4200
1127 851 8300
1128 850 4200
1127 890 6400

5910 893 5608
5910 893 5612
5910 890 0300
5910 890 0310
0812 542 2104
5910 893 8800
5910 890 2210

5910 890 2800

0000 890 2201
1117 890 0900
5910 890 2400

5910 893 0501
5910 850 3100
5910 890 3100
1127 893 2400

1122 893 4600

Application

Blocking the crankshaft
Compressing piston rings
Removing oil seals

Removing flywheel
Attaching connectors
to electric wires
Fitting piston pin
Testing carburetor and crankcase
for leaks
Testing crankcase
for leaks
Sealing exhaust port for
leakage test

Leakage test
Setting air gap between ignition
module and flywheel
Crankshaft nut

Screwed assemblies 1)
Screwed assemblies 1)
For spline screws
Removing pickup bodies
Fitting hookless snap rings
in piston
Detaching springs from
clutch shoes
Flaring rope guide bush
Attaching the brake spring
For all IS screws 2)

Removing bar mounting studs
Holds saw in position for repairs

Installing oil seals
Installing oil pump
Fitting oil seals
Guides press sleeve for
oil pump installation

Remarks

1) DG screws must always be tightened with a torque wrench.

2) In case of DG screws, use for releasing only.

STIHL 029, 039 83

12.2 Servicing Aids

No.

1

2

3

4

5

6

7

8

9

Part Name

Lubricating grease

High-strength
threadlocking (Loctite 270)

High-strength threadlocking
(Loctite 649)

Standard commercial,
solvent-based degreasant
containing no CFCs

STIHL special lubricant

Ignition lead HTR
10 m (33')

Molykote grease

Graphite grease

Elektrician's repair kit

Part No.

0781 120 1111

0786 111 1109

0786 110 0119

0781 417 1315

0000 930 2251

0000 007 1013

Application

Oil seals, oil pump drive, chain
sprocket bearing

Throttle and choke shutter
and fastening screws,
sealing plate and plug

Threads of bar mounting studs
(sprocket side)

Cleaning crankshaft stub
and taper in flywheel

Bearing bore in rope rotor, rewind spring in
starter

Sliding and pivot points of brake band

Peg on starter pawl

10

11

12

Elastosil sealant

Dirko sealant,
100 g (3 1 /2 oz)

STIHL multipurpose grease

0783 830 2120

0781 120 1109

Outer diameter of oil seals

Engine pan, cylinder

Packing high voltage output on ignition
module