STIHL SR 430, STIH)

STIH)

RA_454_ 00_01_01 1. Introduction and Safety Precautions 3 1.1 Introduction 3 1.2 Safety Precautions 4 2. Specifications 5 2.1 Engine 5 2.2 Fuel System 5 2.3 Ignition System 5 2.4 Tightening Torques 6 3. Troubleshooting 8 3.1 Rewind Starter 8 3.2 Blower 9 3.3 Ignition System 10 3.4 Carburetor 12 3.5 Engine 15 4. Engine 16 4.1 Muffler / Spark Arresting Screen 16 4.2 Leakage Test 17 4.2.1 Preparations 17 4.2.2 Vacuum Test 18 4.2.3 Pressure Test 18 4.3 Oil Seals 19 4.4 Shroud 19 4.5 Engine 20 4.6 Cylinder / Crankshaft 22 4.7 Bearings / Crankshaft 25 4.8 Piston 26 4.8.1 Piston Rings 29 5. Ignition System 30 5.1 Ignition Timing 30 5.2 Ignition Module 30 5.3 Testing

the Ignition Module 32 5.4 Spark Plug Boot 33

5.5 Flywheel 34

5.6 Short Circuit Wire 35

5.6.1 Testing 35 5.6.2 Removing and Installing 35 5.6.3 Ground Wire 38 5.7 Ignition System Troubleshooting 39 6. Rewind Starter 42 6.1 General 42 6.2 Starter Cover 42 6.3 Pawl 42 6.4 Rope Rotor 43 6.5 Starter Rope / Grip 44 6.6 Tensioning the Rewind Spring 45 6.7 Replacing the Rewind Spring 46 7. Servicing the AV System 48 7.1 AV Springs at Rear of Backplate 48 7.2 AV Springs at Bottom of Backplate 49 7.3 AV Springs on Backplate, Metering Unit, SR 450 49 7.4 Stop Buffer on Filter

Housing 50 7.5 Stop Buffer on Shroud 50

8. Control Levers 51 8.1 Switch Positions 51 8.2 Setting Lever 51 8.3 Throttle Trigger/ Interlock Lever 52 8.4 Valve Lever 55 8.5 Metering Lever, SR 450 56

8.5.1 Adjusting the Cable 57

9. Fuel System 58

9.1 Air Filter 58

9.2 Baffle 58

9.3 Air Guide Shroud 59 9.4 Filter Housing 59 9.5 Removing and Installing

the Carburetor 62 9.5.1 Leakage Test 63 9.6 Servicing the Carburetor 64 9.6.1 Metering Diaphragm 64 9.6.2 Inlet Needle 65 9.6.3 Fixed Jet 66 9.6.4 Pump Diaphragm 66 9.6.5 Throttle Lever 67 9.6.6 Rotary Knob 68 9.6.7 Adjusting Screws 69 9.7 Adjusting the Carburetor 70 9.7.1 Basic Setting 70 9.7.2 Standard Setting 71 9.8 Throttle Cable 72 9.8.1 Adjusting the Throttle

Cable 72 9.9 Spacer Flange 73 9.10 Tank Vent 74 9.10.1 Testing 74 9.10.2 Removing and Installing 75 9.10.3 Manual Fuel Pump 75 9.11 Fuel Intake 76 9.11.1 Pickup Body 76 9.11.2 Fuel Hoses 77

9.11.3 Connector 79 9.12 Fuel Tank 80

9.12.1 Fuel Tank Cap 81

Contents

10. Blower and Metering

Attachment 82 10.1 Container, SR 430 82 10.2 Container, SR 450 83 10.3 Metering Unit, SR 450 84 10.4 Cable, SR 450 87 10.5 Pressure Pump 89 10.6 Blower Wheel 90 10.7 Blower Housing, SR 430 91 10.8 Blower Housing, SR 450 95 10.9 Nozzle / Valve 98 10.9.1 Nozzle 98 10.9.2 Valve 99 10.10 Blower Tube 101 10.10.1 Pleated Hose 101 10.10.2 Elbow 101 10.10.3 Hoses 102 11. Backplate 103 11.1 Backplate, SR 430 103 11.2 Backplate, SR 450 103 11.3 Harness 105 11.4 Back Padding 106 12. Special Servicing Tools 107 13. Servicing Aids 109

1. Introduction and Safety Precautions

1.1 Introduction

This service manual contains detailed descriptions of all the repair and servicing procedures specific to this power tool.

You should make use of the illustrated parts lists while carrying out repair work. They show the installed positions of the individual components and assemblies. Refer to the latest edition of the relevant parts list to check the part numbers of any replacement parts. A fault on the machine may have several causes. To help locate the fault, consult the chapter on "Troubleshooting" and the "STIHL Service Training System" for all assemblies.

Refer to the “Technical Information” bulletins for engineering changes which have been introduced since publication of this service manual. Technical information bulletins also supplement the parts list until a revised edition is issued.

The special tools mentioned in the descriptions are listed in the chapter on "Special Servicing Tools" in this manual. Use the part numbers to identify the tools in the

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

Symbols are included in the text and pictures for greater clarity.

The meanings are as follows: In the descriptions:

N Action to be taken as shown in the illustration above the text – Action to be taken that is not

shown in the illustration above the text

In the illustrations: A Pointer

a Direction of movement @ 4.2 =Reference to another

chapter, i.e. chapter 4.2 in this example.

Service manuals and all technical information bulletins are intended exclusively for the use of properly equipped repair shops. They must not be passed to third parties.

Preparations for servicing

Always use original STIHL replacement parts.

They can be identified by the STIHL part number, the { logo and the STIHL parts symbol K This symbol may appear alone on small parts.

Storing and disposing of oils and fuels

Collect fuel or lubricating oil in a clean container and dispose of it properly in accordance with local environmental regulations.

1.2 Safety Precautions

If the machine is started up in the course of repairs or maintenance work, observe all local and country-specific safety regulations as well as the safety precautions and warnings in the instruction manual. Gasoline is an extremely flammable fuel and can be explosive in certain conditions.

Always wear suitable protective gloves for operations in which components are heated for assembly or disassembly. Improper handling may result in burns or other serious injuries. Do not smoke or bring any fire, flame or other source of heat near the fuel. All work with fuel must be performed outdoors only. Spilled fuel must be wiped away immediately.

Always perform leakage test after working on the fuel system and the engine.

Always replace damaged parts. Check disassembled parts for wear or damage before re-installing – replace as necessary.

Run the machine only with the shroud mounted in position – there is otherwise a risk of injury from the flywheel and a risk of engine damage due to overheating.

The chapter on tightening torques lists all machine components that have to be tightened to a specific torque. The specifications must be maintained when tightening down screws, nuts and other fasteners in all the procedures described in this service manual.

Fuel system – hose barb connectors

Pull off or push on fuel hoses in line with the connector, preferably by hand, to ensure the tightness of the fuel system.

Avoid damaging the hose barb – do not use sharp-edged pliers, screwdrivers, etc.

Do not cut open fuel hoses with a knife or similar tool.

Do not re-use fuel hoses after removal. Always install new hoses – fuel hoses can be overstretched during removal.

Install new fuel hoses either dry or with the aid of STIHL press fluid, b 13.

Other press fluids are not approved and may result in damage to the fuel hoses.

Coat the ends of the hoses and the connectors with STIHL press fluid and then push the new hoses on to the hose barbs, b 13.

2. Specifications 2.1 Engine SR 430 SR 450 Displacement: 63.3 cm3 63.3 cm3 Bore: 48.0 mm 48.0 mm Stroke: 35.0 mm 35.0 mm

Engine power to ISO 7293: 2.9 kW (3.9 bhp) 2.9 kW (3.9 bhp) Maximum permissible engine speed

(with nozzle) 6,800 rpm 6,800 rpm

Idle speed: 3,000 rpm 3,000 rpm

Crankcase leakage test

at gauge pressure: 0.5 bar

under vacuum: 0.5 bar

2.2 Fuel System

Carburetor leakage test at

gauge pressure: 0.8 bar Operation of tank vent at

gauge pressure: 0.5 bar

Fuel: as specified in instruction manual

2.3 Ignition System

Air gap between ignition

module and fanwheel: 0.15...0.30 mm Spark plug (resistor type): NGK BPMR 7 A

Bosch WSR6F Electrode gap: 0.5 mm

2.4 Tightening Torques

DG and P (Plastoform) screws are used in polymer and light metal components. These screws form a permanent thread when they are installed for the first time. They can be removed and installed as often as necessary without impairing the strength of the screwed assembly, providing the specified tightening torque is observed.

For this reason it is essential to use a torque wrench.

Fastener Thread size For component Torque Remarks Nm

Screw P 5x18 Shroud/blower housing 4.0 2)

Screw P 4x12 Cover/housing 2.0

Screw P 5x18 Cover/inner handle molding 2.0 Screw P 5x18 Antistatic/blower housing 4.0 Screw P 5x25 Pressure pump/blower housing 3.0 Screw M 5x21 Filter cover/filter housing 4.0 Screw P 5x18 Filter housing/blower housing 4.0 Nut M 5 Filter housing/carburetor/baffle 3.5 Screw P 6x25 Blower housing/bearing plug 6.0 Screw P 5x18 Blower housing, outer/inner 4.0

Screw D 6x32 Blower housing, inner/engine pan 12.0 3) Screw D 6x32 Blower housing, inner/cylinder 12.0 3) Nut M 10x1 Blower wheel/crankshaft/nut 30.0

Screw P 5x18 Housing/blower housing 4.0

Screw P 4x19 Handle molding, outer/inner 1.5 Screw P 6x21.5 Handle molding/blower tube 4.0 Screw P 6x25 Lever/inner handle molding 4.0

Screw M 4x9.6 Exhaust pipe/muffler 4.0

Screw M 6x28 Engine pan/cylinder, stage 1 4.0 3), 5) Screw M 6x28 Engine pan/cylinder, stage 2 12.0 3) Screw P 5x18 Air guide shroud/blower housing 4.0

Screw P 4x19 Detent spring/inner handle molding 1.5

Screw P 6x25 Backplate/bearing plug 6.0

Screw P 6x25 Backplate/tank housing 6.0

Screw P 6x25 Backplate/bracket 6.0

Screw P 5x14 Back padding/backplate 2.5

Screw M 5x18 Muffler/cylinder, top, gasket 8.0 3) Screw M 5x18 Muffler/cylinder, bottom 8.0 3) Screw P 6x21.5 Hose clamp/blowing attachment 1.5

Nut M 8x1 Flywheel/crankshaft 20.0 4)

Screw P 5x18 Strainer/blower housing 3.0

Fastener Thread size For component Torque Remarks Nm

M 14x1.25 Spark plug 25.0

Screw M 5x20 Ignition module/engine pan 6.0 1)

Screw M 5x20 Spacer flange/cylinder 6.0 3)

Remarks:

1) Micro-encapsulated with washer 2) Anti-friction coating

3) Binding head screw with anti-friction coating 4) Degrease joint and mount oil-free

5) Seal components with Dirko HT red sealant

Use the following procedure when refitting a DG or P screw in an existing thread: Place the screw in the hole and rotate it counterclockwise until it drops down slightly. Tighten the screw clockwise to the specified torque.

Coat micro-encapsulated screws with medium-strength threadlocking adhesive before re-installing.

This procedure ensures that the screw engages properly in the existing thread and does not form a new thread and weaken the assembly.

Power screwdriver setting for polymer: DG and P screws max. 500 rpm Do not use an impact wrench for releasing or tightening screws. Do not mix up screws with and without binding heads.

3. Troubleshooting

3.1 Rewind Starter

Condition Cause Remedy

Starter rope broken Rope pulled out too vigorously as far as stop or over edge, i.e. not vertically

Fit new starter rope

Normal wear Fit new starter rope

Starter rope does not rewind Very dirty or corroded Clean or replace rewind spring Insufficient spring tension Check rewind spring and increase

tension

Rewind spring worn Fit new rewind spring

Starter rope cannot be pulled out

far enough Rewind spring overtensioned Check rewind spring and reduce tension

Starter rope can be pulled out almost without

resistance (crankshaft does not turn)

Guide peg on pawl or pawl itself is

worn Fit new pawl

Pawl spring fatigued Fit new pawl spring

Starter rope is difficult to pull or

rewinds very slowly Starter mechanism is very dirty Thoroughly clean complete starter mechanism Lubricating oil on rewind spring

becomes viscous at very low outside temperatures (spring windings stick together)

Coat rewind spring with standard solvent-based degreasant (containing no chlorinated or halogenated hydrocarbons), then pull the rope carefully several times until normal action is restored

3.2 Blower

Always switch off the engine before working on the blower.

Condition Cause Remedy

Blower does not blow Blower wheel loose Tighten down nut on blower wheel firmly

Blower wheel blocked Clean blower housing Blower wheel worn or too many

3.3 Ignition System

Exercise extreme caution while carrying out maintenance and repair work on the ignition system. The high voltages which occur can cause serious or fatal accidents.

Condition Cause Remedy

Engine runs roughly, misfires,

temporary loss of power Spark plug boot is loose Press boot firmly onto spark plug and fit new spring if necessary Spark plug sooted, smeared with oil Clean the spark plug or replace if

necessary. Fuel/oil mixture

– too much oil Use correct mixture of fuel and oil Incorrect air gap between ignition

module and flywheel Set air gap correctly Flywheel shows signs of

damage (e.g. scores) or pole shoes have turned blue

Install new flywheel

Ignition timing out of adjustment, flywheel warped, key in flywheel sheared

Install new flywheel

Flywheel magnetization weak –

pole shoes have turned blue Install new flywheel

Irregular spark Check operation of stop switch and ignition module.

Faulty insulation or break in ignition lead or short circuit wire. Check ignition lead/ignition module and replace ignition module if necessary.

Check operation of spark plug. Clean the spark plug or replace if necessary.

Condition Cause Remedy

No spark Spark plug faulty Install new spark plug Faulty insulation or short in short

circuit wire Check short circuit wire for short circuit to ground Break in ignition lead or insulation

damaged Check ignition lead, replace ignition module if necessary Ignition module faulty Install new ignition module

3.4 Carburetor

Condition Cause Remedy

Carburetor floods

– engine stalls Inlet needle not sealing – Foreign matter between valve seat and sealing cone or sealing cone worn

Remove and clean the inlet needle, clean the carburetor

Inlet control lever sticking on spindle

Clean the inlet control lever or replace if necessary.

Helical spring not located on nipple

of inlet control lever Remove the inlet control lever and refit it correctly Perforated disc on metering

diaphragm is deformed and presses constantly against the inlet control lever

Fit a new metering diaphragm

Poor acceleration Setting of low speed screw (L) too

lean Check basic carburetor setting, correct if necessary Setting of high speed screw (H) too

lean Check basic carburetor setting, correct if necessary Inlet needle sticking to valve seat Remove inlet needle, clean and

refit

Diaphragm gasket leaking Fit new diaphragm gasket Metering diaphragm damaged or

shrunk

Fit a new metering diaphragm

Condition Cause Remedy Engine will not idle, idle speed too

high Throttle shutter opened too wide by idle speed screw (LA) Reset idle speed screw (LA) correctly Oil seals/engine leaking Seal or replace oil seals/engine Throttle shutter stiff or torsion

spring on throttle shaft fatigued or broken

Free off throttle shaft or install new carburetor

Engine stops while idling Idle jet bores or ports blocked

Clean the carburetor

Setting of low speed screw (L) too

rich or too lean Reset low speed screw (L) correctly Setting of idle speed screw (LA )

incorrect – throttle shutter completely closed

Reset idle speed screw (LA) correctly

Condition Cause Remedy Engine speed drops quickly under

load – low power Air filter dirty Clean air filter or replace if necessary

Throttle shutter not opened fully Check throttle cable Tank vent faulty Replace tank vent

Fuel pickup body dirty Install new fuel pickup body Fuel strainer dirty Clean fuel strainer in carburetor,

replace if necessary

Leak in the fuel suction hose Install new fuel suction hose Setting of high speed screw (H) too

rich Check basic carburetor setting, correct if necessary Main jet bores or ports blocked Clean or replace the carburetor

Pump diaphragm damaged or

3.5 Engine

Always check and, if necessary, repair the following parts before looking for faults on the engine: - Air filter

- Fuel system - Carburetor - Ignition system

Condition Cause Remedy

Engine does not start easily, stalls at idle speed, but operates normally at full throttle

Oil seals in crankcase damaged Replace the oil seals

Engine leaking or

damaged (cracks) Seal or replace the engine Seal on engine pan leaking Re-seal the engine pan

Engine does not deliver full power

or runs erratically Muffler / spark arresting screen carbonized Clean the muffler (inlet and exhaust), replace spark arresting screen, replace muffler if necessary Air filter dirty Replace air filter

Tank vent faulty Check the tank vent and replace if necessary.

Fuel suction hose kinked or torn Fit new hose or position it free from kinks

Piston rings worn Fit new piston rings

Engine overheating Insufficient cylinder cooling. Air outlets on blower housing blocked or cooling fins on cylinder very dirty

Thoroughly clean all cooling air openings and the cylinder fins

4. Engine

4.1 Muffler / Spark Arresting

Screen

Always check and, if necessary, repair the fuel system, carburetor, air filter and ignition system before looking for faults on the engine. – Troubleshooting, b 3.5 – Remove the shroud, b 4.4

: Take out the screws (arrows). : Remove the muffler (1).

: Remove the gasket (1).

0002RA002 TG

1

0002RA003 TG

1

Installing

: Inspect and clean the sealing faces (arrows), b 13

– Insert the screws through the upper holes in the muffler. : Push the gasket (1) over the

screws – the gasket is held in position.

– Carefully place the muffler (1) in

0002RA006 TG 0002RA007 TG

1

2

2

1

– Fit the screws (2)

– do not tighten down yet.

: Fit the screw (1).

– Tighten down screws (1) and (2) firmly.

Spark arresting screen (country-specific option)

: Take out the screws (1) and remove the exhaust pipe (2).

0002RA009 TG

2

2

1

1

2

1

: Remove the spark arresting screen (1).

– Clean the spark arresting screen with bushing (1) or replace if necessary.

– Reassemble in the reverse sequence.

– Fit the shroud, b 4.4

4.2 Leakage Test

Defective oil seals and gaskets or cracks in castings are the usual causes of leaks. Such faults allow supplementary air to enter the engine and upset the fuel-air mixture.

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.

Always perform the vacuum test first and then the pressure test. The engine can be checked thoroughly for leaks with the pump 0000 850 1300.

0002RA005 TG

1

– Remove the shroud, b 4.4 – Pull off the spark plug boot

vertically.

: Unscrew the spark plug (1). – Set the piston to top dead center.

This can be checked through the spark plug hole.

: Fit the spark plug (1) and tighten it down firmly.

: Loosen the screws (arrows). : Pull the muffler (1) out a little.

0002RA010 TG

1

0002RA011 TG

1

: Fit the sealing plate (1) 0000 855 8106 between the cylinder exhaust port and muffler and tighten down the screws moderately.

The sealing plate must completely fill the space between the two screws.

– Remove the carburetor, b 9.5

Check that the gasket (1) is in position.

: Fit the test flange (1) 5910 850 4200. 0002RA012 TG

1

1

1

: Fit the nuts (arrows) and tighten them down firmly.

4.2.2 Vacuum Test

Oil seals tend to fail when subjected to a vacuum, i.e. the sealing lip lifts away from the crankshaft during the piston's induction stroke because there is no internal counterpressure. A test can be carried out with pump 0000 850 1300 to detect this kind of fault.

: Connect pressure hose (1) of pump 0000 850 1300 to the nipple (arrow).

0002RA015 TG

0002RA016 TG

1

: Push ring (1) to the left. : Operate the lever (2) until the

pressure gauge (arrow) indicates a vacuum of 0.5 bar.

If the vacuum reading remains constant, or rises to no more than 0.3 bar within 20 seconds, it can be assumed that the oil seals are in good condition.

However, if the pressure continues to rise (reduced vacuum in the engine), the oil seals must be replaced, b 4.3.

– After finishing the test, push the ring to the right to vent the pump. – Continue with pressure test,

b 4.2.3

1

2

0002RA017 TG

4.2.3 Pressure Test

Carry out the same preparations as for the vacuum test, b 4.2.2 – Always carry out the pressure

test after the vacuum test, b 4.2.2

: Connect pressure hose (1) of pump 0000 850 1300 to the nipple (arrow).

: Push ring (1) to the right. : Operate the lever (2) until the

pressure gauge (arrow) indicates a pressure of 0.5 bar. If this pressure remains constant for at least 20 seconds, the engine is airtight.

– If the pressure drops, the leak must be located and the faulty part replaced. 0002RA016 TG

1

1

2

To find the leak, coat the suspect area with oil and pressurize the engine. Bubbles will appear if a leak exists.

– After finishing the test, push the ring to the left to vent the pump –

disconnect the hose. – Remove the test flange. – Install the carburetor, b 9.5 – Loosen the screws on the muffler

and pull out the sealing plate. – Tighten down the muffler screws

firmly.

– Reassemble all other parts in the reverse sequence.

4.3 Oil Seals

The engine must be disassembled to replace the oil seals.

– Remove the engine, b 4.5 – Remove the engine pan, b 4.6

– Pull the crankshaft upwards a little but not out of the cylinder. : Pull off the oil seals (1).

– Clean the sealing faces and install new oil seals, b 4.6 – Install the engine pan, b 4.6 – Degrease the crankshaft taper,

b 13

– Install the engine, b 4.5

0002RA462 TG

1

1

4.4 Shroud

– Remove the starter cover, b 6.2

: Take out the screws (arrows).

: Take out the screw (1).

: Lift the shroud (1) slightly and pull it away. 0002RA169 TG 0002RA170 TG

1

1

Installing

Make sure the protective tube is properly seated.

: Place the shroud with the contour (arrow) against the engine pan (1) and push it into position.

: Push the stop buffer (1) onto the tapered pin (2). 0002RA172 TG 0002RA173 TG

1

2

1

: Push home the shroud (1) until it is properly seated.

: The air guide shroud must engage the guide (arrow).

: Insert the screws (arrows) and tighten them down firmly.

: Tighten down the screw (1) firmly. 0002RA175 TG

1

1

The complete engine has to be removed for access to the piston, cylinder and crankshaft.

– Remove the air guide shroud, b 9.3

: Disconnect the short circuit wire (1) and ground wire (2). – Put the wires to one side.

0002RA024 TG

0002RA025 TG

1

2

: Pull the wiring harness (1) out of the guide (arrow).

– Remove the carburetor, b 9.5 – Remove the container,

SR 430 b 10.1, SR 450 b 10.2

– Remove the metering unit, SR 450, b 10.3

– Remove the blower wheel, b 10.6

: Take out the screws (arrows).

: Push the complete engine (1) out

0002RA026 TG

1

0002RA027 TG

0002RA028 TG

1

– Check the engine and, if necessary, replace the cylinder, piston, crankshaft or crankcase – the muffler, ignition module and spacer flange must be remove for this purpose.

– Inspect the oil seals and replace if necessary, b 4.3

– Check correct position of the oil seals

– they must be properly located in their seats.

Installing

Take care to avoid pinching the short circuit and ground wires between the engine and blower housing.

: Push the straight crankshaft stub (1) into the blower housing bore (arrow).

0002RA029 TG

0002RA030 TG

1

– Push the engine against the blower housing.

– Position the engine against the blower housing and hold it there – line up the holes in the engine and blower housing.

: Insert the screws (arrows) and tighten them down firmly. – Install the blower wheel, b 10.6 – Fit the blower housing,

SR 430 b 10.7, SR 450 b 10.8

The wiring harness (1) must be in the guide (arrow).

: Connect the ground wire (2) and short circuit wire (1) – make sure the connectors are pushed fully home.

– Reassemble all other parts in the reverse sequence. 0002RA026 TG

1

1

2

– Remove the engine, b 4.5

– Remove the muffler (1), b 4.1 – Remove the ignition module (2),

b 5.2

– Remove the flywheel (3), b 5.5

: Take out the screws (arrows).

0002RA035 TG

1

2

3

0002RA036 TG

: Pull off the engine pan (1). Do not use pointed or sharp-edged tools for this job.

: Release the crankshaft (1) from its bearing seats (arrows) and pull it carefully out of the cylinder.

: Pull off the oil seals (1).

0002RA037 TG

1

1

1

1

– Inspect and clean the sealing faces and seats of the oil seals (arrows) and remove any gasket residue if necessary, b 13

The sealing faces must be in perfect condition. Always replace

components with damaged sealing faces, b 3.5.

New sealant must be applied every time the cylinder or engine pan is removed.

– Inspect the spacer flange (1) and replace it if necessary – even very minor damage can result in engine running problems, b 3.5 If a new cylinder is being installed, the spacer flange may be

transferred from the old cylinder if it is in good condition.

: Take out the screws (arrows). – Remove the spacer flange (1).

0002RA050 TG

0002RA041 TG

1

: Remove the gasket (1).

: Inspect and clean the sealing face (arrow) and remove any gasket residue, b 13

– Inspect the sealing faces on exhaust port.

The sealing faces must be in perfect condition. If the sealing faces are damaged, install a new cylinder. – Inspect the piston and piston rings and replace if necessary, b 4.8

0002RA042 TG

1

0002RA043 TG

Installing

– Lubricate the piston, piston rings and cylinder wall with oil, b 13 : Use the clamping strap (1)

4244 893 2600 to compress the rings around the piston.

– Check correct installed position of rings, b 4.8.1

Apply the clamping strap (1) so that the piston rings do not project beyond the cylinder wall.

– Close the clamping strap (arrow).

The arrow (1) on the clamping strap must point in the direction of the recess (arrow) in the cylinder.

0002RA045 TG

1

0002RA458 TG

– Position the piston with clamping strap on the cylinder and hold it steady.

While sliding the piston into the cylinder, check that the clamping strap is tightly around the piston and the rings do not project

– they might otherwise break. : Carefully slide the piston into the

cylinder. The clamping strap is pushed off in the process.

: Open and remove the clamping strap (1).

0002RA459 TG

0002RA460 TG

1

: Rotate the crankshaft until the tapered crankshaft stub (1) points in the direction of the bosses (arrows) on the cylinder.

: Lubricate sealing lip (arrows) of new oil seal with grease, b 13

– Fit the installing sleeve (1) 1118 893 4602 on each side before pushing the oil seals into place. 0002RA461 TG

1

1

2

1

2

: Apply thin coating of sealant to outside diameter (arrows) of the oil seals, b 13

: Place the crankshaft with bearings and oil seals in the bearing seats, making sure the oil seals are firmly against their stops (arrows) in the crankcase.

: Apply sealant to the groove in the sealing face, b 13 0002RA463 TG 0002RA464 TG

1

– Hold the engine pan (1) so that the ignition module mounting (arrow) points in the direction of the tapered crankshaft stub. : Place the engine pan (1) in

position.

: Fit the screws (arrows) and secure the engine pan in position. – Tighten down the screws firmly in

a crosswise pattern.

– Install the spacer flange, b 9.9 – Install the muffler, b 4.1

– Install the ignition module, b 5.2 – Reassemble all other parts in the

reverse sequence.

0002RA467 TG

1

0002RA049 TG

4.7 Bearings / Crankshaft

– Remove the crankshaft, b 4.6 – Pull off the oil seals, b 4.6

: Pull the ball bearing (1) off the tapered crankshaft stub.

: Pull the ball bearing (1) off the straight crankshaft stub.

: The crankshaft (1), connecting rod (2) and needle bearing form an inseparable unit. It must always be replaced as a complete unit. 296RA064 TG

1

1

2

1

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

– Clean the crankshaft before installing the bearings, b 13

Installing

: Position the ball bearing (1), closed side facing outwards, on the straight crankshaft stub. – Heat the inner bearing race to

about 150°C (300°F).

: Push the ball bearing onto the straight crankshaft stub as far as stop.

This operation must be carried out very quickly because heat is absorbed by the crankshaft, and the inner bearing race shrinks.

0002RA457 TG

Use a firm base (2) to protect the crankshaft.

: If it is not possible to heat the ball bearing, apply a suitable

sleeve (1) to the inner race and press the bearing onto the straight crankshaft stub as far as stop.

– Position the ball bearing (1), closed side facing outwards, on the tapered crankshaft stub. – Heat the inner bearing race to

about 150°C (300°F).

: Push the ball bearing (1) onto the tapered crankshaft stub as far as stop.

This operation must be carried out very quickly because heat is absorbed by the crankshaft, and the inner bearing race shrinks.

296RA067 TG

1

2

0002RA465 TG

1

Use a firm base (2) to protect the crankshaft.

: If it is not possible to heat the ball bearing, apply a suitable

sleeve (1) to the inner race and press the bearing onto the tapered crankshaft stub as far as stop.

– Lubricate the needle bearing with oil.

– Install the piston, b 4.8 – Fit new oil seals and install the

crankshaft, b 4.6 – Install the engine, b 4.5

– Reassemble all other parts in the reverse sequence.

0002RA478 TG

1

2

4.8 Piston

– Remove the engine, b 4.5 – Remove the crankshaft, b 4.6

: Use a suitable tool to grip the hookless snap ring at the recess (arrow) and ease it out. The assembly drift can be pushed through the second snap ring, which does not have to be removed.

: Apply the assembly drift (1) 1108 893 4700, small diameter first, to the ignition side of the piston.

0002RA370 TG

0002RA057 TG

: Use the assembly drift (2) 1108 893 4700 to push the piston pin out of the piston.

If the piston pin is stuck, release it by tapping the end of the drift lightly with a hammer.

Hold the piston steady during this process to ensure that no jolts are transmitted to the connecting rod.

: Remove the piston (1) from the connecting rod.

– Inspect the piston rings and replace it if necessary, b 4.8.1 0002RA058 TG

2

1

1

: Remove the needle cage (1).

Installing

– Lubricate the needle cage with oil and push it into the connecting rod.

: Line up the piston as shown so that the arrow (arrow) on the piston crown faces to the rear and the tapered crankshaft stub (1) is on the right. : Place the piston on the

connecting rod.

11

0002RA060 TG

1

: Push the assembly drift (1) 1108 893 4700, small diameter first, through the side of the piston with the installed snap ring and the small end (needle bearing).

: Fit the piston pin (2) on the assembly drift (1) and slide it into the piston.

: Remove the sleeve (1)

5910 893 1706 from the installing tool (2) 5910 890 2212. 0002RA061 TG

1

1

2

1

2

: Attach the snap ring (1) to the magnet (2) so that the snap ring gap is on the flat side of the tool's shank (arrow).

: Push the large slotted diameter of the sleeve 5910 893 1706 over the magnet and snap ring. The inner pin (1) must point towards the flat face (2) of the tool's shank.

533RA128 TG

1

2

1

2

: Press the installing tool

downwards into the sleeve until the magnet butts against the end of the guide slot.

Use a suitable base (wooden board).

: Remove the sleeve and push it on to the other end of the shank as far as stop.

The inner pin (arrow) must again point towards the flat face.

0001RA483 TG

533RA131 TG

– Install the snap ring at the blower side of the piston.

: Apply the installing tool

5910 890 2212 with the sleeve’s taper against the piston boss, hold the piston steady, center the tool shank exactly and press home until the snap ring slips into the groove.

Make sure the tool shank is held square on the piston pin axis.

Fit the snap ring (1) so that its gap (arrow) points down – it must not be near the recess (2).

– Check installed position of snap ring.

0002RA371 TG

0002RA456 TG

– Inspect the piston rings and replace if necessary, b 4.8.1 – Install the crankshaft, b 4.6 – Install the engine, b 4.5

– Reassemble all other parts in the reverse sequence.

0002RA063 TG

4.8.1 Piston Rings

– Remove the piston, b 4.8 – Remove the piston rings from the

piston.

: Use a piece of old piston ring to scrape the grooves (arrows) clean.

: Position the new piston rings in the groove so that the

radii (arrows) at the ring gaps face upwards.

0002RA366 TG

0002RA104 TG

: Position the piston rings so that the radii at the ring gap meet at the fixing pin in the piston groove (arrows).

– Check correct installed position of the piston rings (arrows). – Install the piston, b 4.8

– Reassemble all other parts in the reverse sequence.

5. Ignition System

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

Troubleshooting on the ignition system should always begin at the spark plug, b 3.3

– Remove the shroud, b 4.4

The electronic (breakerless) ignition system basically consists of an ignition module (2) and flywheel (1).

5.1 Ignition Timing

Ignition timing is fixed and cannot be adjusted during repair work. Since there is no mechanical wear in these systems, ignition timing cannot get out of adjustment during operation.

0002RA064 TG

1

2

5.2 Ignition Module

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

– High voltage output (1) with ignition lead

– Connector tag (2) for the short circuit wire

Testing in the workshop is limited to a spark test. A new ignition module must be installed if no ignition spark is obtained (after checking that wiring and stop switch are in good condition), b 5.3

0002RA065 TG

1

2

Removing

– Remove the shroud, b 4.4 : Pull off the spark plug boot (1)

vertically.

: Pull the ignition lead (1) out of the guides (arrows).

: Disconnect the short circuit wire (1) and ground wire (2).

0002RA066 TG

1

1

1

2

: Take out the screw (3) and washer.

– Remove the connector tag (1). : Take out the screw (2) and

washer.

: Remove the ignition module (1).

The ignition module (1) and ignition lead (2) form a unit.

– Check the spark plug boot and replace if necessary, b 5.4 – Troubleshooting, b 3.3 0002RA067 TG

2

1

3

1

2

1

: Hold the wiring harness (1) in the direction of the carburetor so that it cannot be pinched.

: Position the ignition module (1) so that the ignition lead (2) points towards the carburetor.

: Fit the screw (3) with washer – do not tighten down yet.

0002RA000 TG

1

0002RA070 TG

2

1

3

: Fit the connector tag (1) and insert the screw (2) with washer – do not tighten down yet.

– Push the ignition module (1) back.

: Slide the setting gauge (2) 4118 890 6401 between the arms of the ignition module and the flywheel magnet.

0002RA071 TG

1

2

1

2

The setting gauge is not shown in the illustration.

– Push the ignition module (1) back – the flywheel must move freely. : Rotate the flywheel until the

magnet poles (arrows) are next to the ignition module (1). – Press the ignition module against

the setting gauge.

– Tighten down the screws firmly. – Remove the setting gauge. – Check operation

– rotate the flywheel and make sure it does not touch the ignition module.

: Starting at the ignition module, attach the ignition lead (1) to the guides (arrows). N S 0002RA073 TG

1

1

: Connect the ground wire (2) and short circuit wire (1) – make sure the connectors are pushed fully home.

– Push the boot onto the spark plug.

– Reassemble all other parts in the reverse sequence.

5.3 Testing the Ignition

Module

To test the ignition module, use either the ZAT 4 ignition system tester 5910 850 4503 or the ZAT 3 ignition system tester

5910 850 4520.

The ignition test refers only to a spark test, not to ignition timing.

0002RA033 TG

1

2

Using ZAT 4 ignition system 5910 850 4503

– Before starting the test, install a new spark plug in the cylinder and tighten it down firmly. : Connect spark plug boot to the

input terminal (1). Push the tester’s output terminal (3) on to the spark plug.

High voltage – risk of electric shock. : Crank the engine quickly with the rewind starter and check spark in the tester’s window (2).

The engine may start and accelerate during the test. If a spark is visible, the ignition system is in order.

If no spark is visible in the window (2), check the ignition system with the aid of the troubleshooting chart, b 5.7

165RA183 TG

Using the ZAT 3 ignition tester 5910 850 4520

– Before starting the test, install a new spark plug in the cylinder and tighten it down firmly. – Connect spark plug boot to the

terminal (2).

: Attach the ground terminal (1) to the spark plug.

: Use adjusting knob (3) to set the spark gap to about 2 mm.

While using the ZAT 3, hold it only by the handle (4) or position it in a safe place. Keep fingers or other parts of your body at least 1 cm away from the spark window (3), high voltage connection (2), ground connection (5) and the ground terminal (1).

High voltage – risk of electric shock.

296RA100 TG

1

2

3

1

2

3 4

5

– Crank the engine quickly with the rewind starter and check spark in the tester’s window (3).

The engine may start and accelerate during the test. If a spark is visible, the ignition system is in order.

If no spark is visible in the window (3), check the ignition system with the aid of the troubleshooting chart, b 5.7

5.4 Spark Plug Boot

The ignition module (1) and ignition lead (2) form a unit. A new ignition module must be installed if the ignition lead is damaged. – Pull off the spark plug boot

vertically.

– Remove the shroud, b 4.4

: Use suitable pliers to pull the leg spring out of the spark plug boot. – Unhook the leg spring from the

ignition lead.

– Pull the boot off the ignition lead.

0002RA074 TG

Installing

Do not shorten the ignition lead.

– Use a pointed tool to pierce the center of the new ignition lead’s insulation, about 15mm from the end of the lead.

: Pinch the hook of the leg spring into the pierced hole in the center of the lead (arrow).

– Coat the inside of the spark plug boot with STIHL press fluid, b 13

: Hold the ignition lead and leg spring together and push them into the spark plug boot.

165RA188 TG

: Make sure the leg spring (arrow) locates properly inside the spark plug boot.

Do not use either graphite grease or silicone insulating paste.

– Reassemble all other parts in the reverse sequence.

5.5 Flywheel

– Remove the shroud, b 4.4 – Unscrew the spark plug. : Push the locking strip (1)

0000 893 5904 into the spark plug hole until it butts against the cylinder wall

– as shown.

0002RA077 TG

0002RA078 TG

1

: Unscrew the flywheel nut (arrow).

If the flywheel is stuck, use a puller.

: Screw the puller (1)

5910 893 0801 clockwise on to the crankshaft as far as stop, then back it off a 1/4 turn. – Tap the end of the puller to

release the flywheel.

– Take care not to damage the crankshaft stubs and ball bearings.

– Unscrew the puller and remove the flywheel.

0002RA079 TG

0002RA080 TG

1

The flywheel and

magnet poles (arrows) must not be damaged or have turned blue. Replace flywheel if necessary. Before assembly, degrease the bore in the flywheel hub and the crankshaft stub, b 13.

: Make sure the key (arrow) engages the slot in the crankshaft stub.

– Check the air gap between the ignition module and flywheel and adjust if necessary, b 5.2 – Reassemble all other parts in the

reverse sequence.

0002RA081 TG

5.6 Short Circuit Wire

5.6.1 Testing

If the spark plug, ignition lead and spark plug boot are in order, check the short circuit wire and stop switch, b 5.6.2.

– Remove the shroud, b 4.4 : Disconnect the short circuit

wire (1).

– Connect the ohmmeter to ground (arrow) and the short circuit wire (1).

– Move the setting lever to "0" and hold it in that position.

The resistance measured must be about 0 Ω. If it is much higher, the reason may be the stop switch or the wire. If damage is found, replace the complete throttle cable,

b 5.6.2.

– Move the setting lever to "F". The resistance measured must be infinitely high. If not, install a new throttle cable, b 5.6.2.

0002RA083 TG

1

To locate the fault, test the wires for continuity and check insulation for damage. If the wires are in order, check operation of stop switch, b 5.7

If no fault can be found, check the ignition system with the aid of the troubleshooting chart, b 5.7 – Check ground wire for continuity. – Reassemble in the reverse

sequence.

5.6.2 Removing and Installing

The short circuit wire (black), ground wire (blue) and throttle cable are in a protective tube and form an assembly.

If any part is damaged, the entire throttle cable must be replaced. – Remove the shroud, b 4.4 – Remove the filter housing, b 9.4

: Pull off the spark plug boot (1) vertically.

0002RA066 TG

1

: Disconnect the short circuit wire (1) and ground wire (2).

: Pull the wiring harness (1) out of the guides (arrows).

: Pull the fuel hoses (1) out of the guides (arrows). 0002RA025 TG

1

2

1

1

1

: Pull the throttle cable (1) out of the guides (arrows).

– Press down the throttle lever until the nipple (arrow) projects. : Take the throttle cable (1) out of

the pin (2).

: Pull the protective tube (1) out of the guides (arrows).

– Remove the control levers and

0002RA086 TG

1

1

2

1

: Pull the ground wire (1) off the pin (arrow).

: Pull out the stop switch (2).

: Pull the ground and short circuit wires out of the guides (arrows). – Remove the wires with the stop

switch.

: Pull the protective tube (1) out of its seat (arrow) in the handle

0002RA089 TG

1

2

1

– Pull the wires and throttle cable out of the guides.

The stop switch is permanently connected to the short circuit wire. If any part is damaged, the entire throttle cable must be replaced.

Installing

: Push the stop switch (1) onto the pins (arrows).

: Fit the ground wire terminal (1) on the pin (2) with its crimped side facing down.

0002RA092 TG

1

0002RA093 TG

1

: Fit the ground and short circuit wires in the guides (arrows).

: Push the protective tube (1) into its seat (arrow) in the handle molding.

: Push the wires (short circuit wire first) into the guide (arrows) – position the wires parallel without loops.

0002RA474 TG

0002RA094 TG

1

0002RA095 TG

: Push the throttle cable (1) into its seat (arrow).

– Install the valve, b 10.9.2 – Install the control levers and cam,

b 8

– Fit the handle molding (1) in position.

: Insert the screws (arrows) and tighten them down firmly.

– Position the protective tube (1) so that the throttle cable (2) is under the wiring harness (3) in the direction of the blower

0002RA096 TG

1

1

1

2

3

: Push the protective tube (1) into its guides (arrows) as far as stop. – The protective tube is now held in position.

: Attach the throttle cable (1) to the carburetor (2).

: Push the throttle cable (1) into the guides (arrows).

– Check operation of throttle cable and readjust if necessary, b 9.8.1 0002RA099 TG

1

1

2

1

– Position the wiring harness (1) against the blower housing. : Push the wiring harness (1) into

the guides (arrows).

: Connect the ground wire (2) and short circuit wire (1) – make sure the connectors are pushed fully home. 0002RA102 TG

1

1

2

: Push the fuel hoses (1) into the guides (arrows).

– Reassemble all other parts in the reverse sequence.

5.6.3 Ground Wire

A faulty ground wire may impair or prevent operation of the short circuit wire.

The short circuit wire (black), ground wire (blue) and throttle cable are in a protective tube and form an assembly.

If any part is damaged, the entire throttle cable must be replaced. – Check for contact and continuity

and replace the throttle cable if necessary, b 5.6.2

0002RA103 TG

5.7 Ignition System Troubleshooting

Machine does not run

Setting lever:

– in position "F"?

Check the spark plug:

– Smeared with oil, black? – Sooted?

– Electrode gap correct? – Contacts shorted? – Clean or replace the plug

b 5.3

Check the spark plug boot:

– Firmly seated on plug (leg spring)? – Leg spring hook in center of ignition lead?

– Boot damaged?

– If necessary, install new spark plug boot and/ or leg spring,

b 5.4

Test ignition system:

with ZAT 3 or ZAT 4 (use ZAT 3 as main spark gap

see TI 32.94), b 5.3

Check the flywheel:

– Have pole shoes turned blue? – Install new flywheel if necessary,

b 5.5

Air gap:

– Check ignition module/flywheel, – reset if necessary, b 5.2

Check the ignition lead:

– Severe chafing? – Spark plug boot: Holes/cracks? – Resistance: spark plug boot to ground: spec.

1.5 – 12 kΩ

If necessary, install new spark plug boot and/or ignition lead with module,

b 5.2

Check ground and short circuit wires:

– Wire damaged? – Connectors firmly seated? – Check continuity, replace wires or wiring

harness if necessary, b 5.6.2

1

Machine runs trouble-free, no further action necessary

no Install new ignition module

b 5.2

yes

no

– Look for fault in fuel system or carburetor

– Check engine for leaks – Check position of flywheel on

crankshaft, yes

Check operation of stop switch:

– Function of stop switch: – Setting lever on "F" = no connection

– Setting lever on "

0

b 5.6, b 5.6.2

2

3

6. Rewind Starter

6.1 General

If the action of the starter rope becomes very stiff and the rope rewinds very slowly or not

completely, it can be assumed that the starter mechanism is in order but plugged with dirt. At very low outside temperatures the lubricating oil on the rewind spring may thicken and cause the spring windings to stick together. This has a

detrimental effect on the function of the starter mechanism.

In such a case it is sufficient to apply a few drops of a standard solvent-based degreasant (containing no chlorinated or halogenated

hydrocarbons) to the rewind spring. Always wear safety glasses and protective gloves when working on the rewind spring – risk of injury. Carefully pull out the starter rope several times and allow it to rewind until its normal smooth action is restored.

Before installing, lubricate the rewind spring and starter post with STIHL special lubricant.

If clogged with dirt or pitch, the entire starter mechanism, including the rewind spring, must be removed and disassembled. Take particular care when removing the spring. – Clean all components, b 13 – Relieve tension of rewind spring,

b 6.4

6.2 Starter Cover

: Take out the screws (arrows). – Remove the cover (1).

Installing

– Place the cover in position. : Insert the screws (arrows) and

tighten them down firmly.

0002RA105 TG

1

0002RA106 TG

6.3 Pawl

– Remove the starter cover, b 6.2 : Carefully ease the straight end of the spring clip (1) off the starter post.

: Remove the pawls (1).

0002RA107 TG

1

0002RA108 TG

: Fit the new pawls (1) in the bores (arrows) and lubricate the pegs on the pawls with grease, b 13

: Position the spring clip (1) so that its loops engage the pegs on the pawls. The rounded part of the spring clip (short arrow) must engage the starter post’s groove. : Push the straight part of the

spring clip over the starter post until it snaps into the groove.

0002RA109 TG

1

1

0002RA110 TG

1

The spring clip's guide loops must be in line with the pawls (arrows). – Check operation.

– Pull the starter rope. The rope rotor turns and the pegs move in the direction of the spring loop – the pawls swing outwards. – Reassemble all other parts in the

reverse sequence.

6.4 Rope Rotor

Relieving tension of rewind spring

– Remove the starter cover, b 6.2 : Pull out the starter rope (1)

about 5 cm and hold the rope rotor (2) steady.

0002RA111 TG

0002RA112 TG

1

2

– Take three full turns of the rope off the rope rotor.

– Pull out the rope with the starter grip and slowly release the rope rotor.

– Remove the starter rope or remaining rope from the rotor. The system will not be under tension if the starter rope is broken or the rewind spring is worn. – Remove the spring clip and

pawls, b 6.3

: Remove the washer (1). Rewind spring must be relaxed. – Carefully remove the rope

rotor (2).

– The rewind spring may pop out and unwind.

– Remove the starter rope, b 6.5 – Coat starter post and bore in rope

rotor with STIHL special lubricant, b 13

0002RA113 TG

1

Installing

: Fit the rope rotor on the starter post so that the inner spring loop (arrow) engages the recess (1).

– Fit the cover washer.

– Install the pawls and spring clip, b 6.3

– Install the starter rope, b 6.5 – Tension the rewind spring, b 6.6 – Lubricate pegs on pawls with

grease, b 13

– Reassemble all other parts in the reverse sequence.

6.5 Starter Rope / Grip

– Remove the starter cover, b 6.2 – Relieve tension of rewind spring,

b 6.4

The system will not be under tension if the starter rope is broken. – Remove remaining rope from the

rope rotor and starter grip. Do not shorten the starter rope.

0002RA114 TG

1

: Push the end of the starter rope (1) out a little and undo the knot.

– Pull the starter rope out of the rotor.

: Use a suitable tool to pry the cap (1) out of the starter grip.

0002RA115 TG

1

0002RA117 TG

1

: Pull the sleeve, washers, spring and remaining rope (arrow) out of the grip.

– Pull the remaining rope out of the sleeve.

Do not shorten the starter rope.

– Thread the new starter rope through the sleeve.

– Tie a simple overhand knot in the end of the new rope.

– Fit the washers and spring. : Thread the starter rope with

sleeve, spring and washers through the starter grip (1). Make sure the washers and spring remain on the sleeve while the rope its being pulled into the grip.

0002RA118 TG

0002RA119 TG

: Position cap so that its lug (1) engages the slot (arrow) in the starter grip.

– Press the cap into the starter grip.

: Thread the starter rope (1) through the guide

bushing (arrow).

: Thread the rope (1) through the hole in the rotor (arrow).

165RA234 TG

1

1

1

– Tie a simple overhand knot in the end of the new rope.

: Pull the rope back until the knot locates in the recess (arrow) in the rope rotor.

– Install the rope rotor and tension the rewind spring, b 6.4, b 6.6 – Fit the starter cover, b 6.2

6.6 Tensioning the Rewind

Spring

– Remove the starter cover, b 6.2 : Pull out a short length of starter

rope (1).

: Use the starter rope (1) to rotate the rope rotor (2) six turns clockwise.

The pawls and spring clip must be installed.

The rewind spring is now tensioned.

0002RA122 TG

0002RA123 TG

1

2

Hold the rope rotor steady since it will otherwise spin back and may damage the rewind spring.

– Hold the rope rotor (2) steady. : Pull out the twisted rope (1) with

the starter grip and straighten it out.

– Hold the starter grip (1) firmly to keep the rope tensioned. : Let go of the rope rotor and

slowly release the starter rope so that it can rewind properly.

0002RA124 TG

1

2

0002RA125 TG

The rewind spring is correctly tensioned when the starter grip sits firmly in the rope guide

bushing (arrow) without drooping to one side. If this is not the case, tension the spring by one additional turn.

When the starter rope is fully extended, it must still be possible to rotate the rope rotor at least another half turn before maximum spring tension is reached. If this is not the case, reduce spring tension since there is otherwise a risk of breakage.

To reduce spring tension:

Pull the rope out, hold the rope rotor steady and take off one turn of the rope.

– Fit the starter cover, b 6.2

0002RA126 TG

6.7 Replacing the Rewind

Spring

– Troubleshooting, b 3.1 The replacement spring comes ready for installation in a spring housing.

– Remove the starter cover, b 6.2 – Relieve tension of rewind spring if necessary and remove the rope rotor, b 6.4

– Remove any remaining pieces of old spring.

– Lubricate the spring with a few drops of STIHL special lubricant before installing, b 13

: Line up the replacement spring and spring housing – the anchor loop (2) must be above the lug (1).

0002RA127 TG

2

1

– Fit the rewind spring with housing in position.

Take care to ensure the rewind spring is not pushed out of the spring housing by the starter post – The rewind spring may pop out and unwind.

: Push the rewind spring with spring housing into its seat in the starter cover.

Make sure that the spring housing (1) is properly seated. If the rewind spring has popped out, refit it in the starter cover as follows: – Arrange the spring in its original

position.

0002RA128 TG

: Engage the outer spring loop (1) on the guide (arrow) in the spring housing.

: Fit the rewind spring (1) in the spring housing (2) in the clockwise direction, from the outside inwards.

– Hold the spring windings so that they cannot pop out.

Make sure the rewind spring is properly

seated.

0002RA129 TG

1

2

– Fit the rewind spring with housing in position.

Take care to ensure the rewind spring is not pushed out of the spring housing by the starter post – The rewind spring may pop out and unwind.

: Push the rewind spring with spring housing (1) into its seat in the starter cover.

Make sure that the spring housing (1) is properly seated. – Install the rope rotor, b 6.4 – Install the pawls, b 6.3 – Lubricate pegs on pawls with

grease, b 13

– Tension the rewind spring, b 6.6 – Reassemble all other parts in the

reverse sequence.

0002RA128 TG

7. Servicing the AV System

The blower housing and backplate are connected by vibration-damping springs.

Damaged springs must always be replaced.

The anti-vibration springs are located between the blower housing and the backplate.

– Remove the blower housing, SR 430 b 10.7,

SR 450 b 10.8

7.1 AV Springs at Rear of

Backplate

: Hold the AV springs (2) steady in their seats and take out the screws (1).

: Remove the AV springs (2).

0002RA130 TG

2

2

1

1

: Unscrew the bearing plugs (1) and (2) from the AV springs. – Screw home the bearing

plugs (1) and (2) as far as stop.

Installing

: Line up the preassembled AV springs (1) so that the

face (arrow) is parallel to the blower wheel.

– Push the AV springs home as far as stop.

0002RA131 TG

1

2

0002RA132 TG

1

– Hold the AV springs (2) steady in their seats.

: Fit and tighten down the screws (1) firmly.

– Reassemble all other parts in the reverse sequence.

0002RA133 TG

2

2

7.2 AV Springs at Bottom of Backplate

: Unscrew the anti-vibration springs (arrows) from the bearing plugs.

: Unscrew the bearing plugs (arrows) from the anti-vibration springs.

– Screw the bearing plugs (1) into the springs as far as stop.

0002RA134 TG

0002RA135 TG

1

Installing

: Screw the preassembled anti-vibration springs onto the bearing plugs (arrow) as far as stop.

– Install the blower housing, SR 430 b 10.7,

SR 450 b 10.8

– Reassemble all other parts in the reverse sequence.

7.3 AV Springs on Backplate,

Metering Unit, SR 450

– Remove the metering unit, b 10.3

: Unscrew the anti-vibration springs from the bearing plugs (arrows) .

0002RA136 TG

0002RA433 TG

: Unscrew the bearing plugs (1) from the anti-vibration springs. – Screw the bearing plugs (1) into

the springs as far as stop.

Installing

: Screw the preassembled anti-vibration springs onto the bearing plugs (arrow) as far as stop.

– Install the metering unit, b 10.3 – Reassemble all other parts in the

reverse sequence.

0002RA135 TG

1

7.4 Stop Buffer on Filter Housing

– Remove the filter housing, b 9.4

: Pull off and replace the stop buffer (1).

Installing

– Use STIHL press fluid to simplify assembly, b 13

: Push the stop buffer (1), tapered end first, into the bore (arrow) as far as stop – the tapered end must slide fully home and engage the bore.

– Install the filter housing, b 9.4 – Reassemble all other parts in the

reverse sequence.

0002RA139 TG

1

0002RA140 TG

1

7.5 Stop Buffer on Shroud

– Remove the shroud, b 4.4

: Pull off and replace the stop buffer (1).

Installing

– Use STIHL press fluid to simplify assembly, b 13

: Push the stop buffer (1), tapered end first, into the bore (arrow) as far as stop – the tapered end must slide fully home and engage the bore.

– Install the shroud, b 4.4

– Reassemble all other parts in the reverse sequence.

0002RA141 TG

1

0002RA142 TG

8. Control Levers

8.1 Switch Positions

On these machines the operating modes are set on the control handle and the carburetor.

– PositionF = normal run position – engine runs or can start – Position

0

– ignition is switched off (no lock in this position, the setting lever returns to the run position)

Version with throttle limiter

– Positions to limit travel of throttle trigger

a = 1/3 throttle b = 2/3 throttle

– to disengage the limiter, return the setting lever to the run positionF.

0002RA143 TG

a

b

Version with throttle lock

– Throttle trigger lock positions a = full throttle

b = half throttle

– to disengage the lock, return the setting lever to the run positionF.

On the carburetor

The rotary knob returns to the run position when the throttle trigger is operated.

– Positione = normal run position – Positiont = warm start

– warm engine is started in this position

– Positionc = cold start – cold engine is started in this position 0002RA503 TG

a

b

– Remove the handle molding, b 8.3

– Remove the cam, b 8.3 : Squeeze the lugs (arrows)

together and push out the setting lever (1).

Installing

– Position the setting lever (1) so that it points in the direction of the symbol (2).

: Push the lugs of the setting lever (1) into the hole (arrow) until it snaps into position. – Fit the handle molding, b 8.3 – Check operation.

1

0002RA146 TG

1

8.3 Throttle Trigger/Interlock Lever

: Take out the screws (arrows). – Remove the handle molding (1). The cam may fall out.

Version with throttle limiter

: Carefully remove the setting lever (1) – tension of torsion spring (2) is suddenly relieved. – Remove the torsion spring (2).

0002RA147 TG

1

0002RA148 TG

1

2

Version with throttle lock

: Remove the cover (1).

Both versions

: Pull off the cam (1).

: Pull the detent spring (1) slightly apart and lift it out over the guides (arrows)

– do not overstretch the detent spring. 0002RA499 TG

1

1

1

2

: Push the detent spring (1) into the guides (arrow) until it snaps into position

– do not overstretch the detent spring.

: Disconnect the leg (arrow) from the lever (1).

– Remove the torsion spring (2).

: Remove the throttle trigger (1) and lever (2). 0002RA151 TG

1

2

1

3

2

1

: Pull the lever (1) off the throttle trigger (2).

Installing

– Check that the grub screw (1) is in place, fit a new grub screw if necessary.

A new throttle trigger comes with the grub screw already fitted. – The throttle cable must be

readjusted if a new throttle trigger is installed or the position of the grub screw is changed, b 9.8.1

0002RA154 TG

1

2

2

1

1

1

The ground and short circuit wires must be properly seated in the guides (arrows).

: Push the lever (1) into the throttle trigger so that it fits snugly against the throttle trigger (arrow).

: Push the throttle cable nipple (1) into the lever and engage it in the slot (arrow). 0002RA157 TG 0002RA158 TG

1

1

1

Version with throttle limiter

: Push the throttle trigger (1) onto the pivot pin.

Version with throttle lock

: Push the throttle trigger (1) onto the pivot pin.

Both versions

: Fit the torsion spring (1) on the throttle trigger and position its short leg against the web (arrow).

0002RA160 TG

1

1

1