Stihl MS 240, MS 260 Instruction Manual

Download

Page 1

STIH)

STIHL MS 240, 260

2013-09

Page 2

RA_165_00_01_05

1. Introduction 3

2. Safety Precautions 5

3. Specifications 6

3.1 Engine 6

3.2 Fuel System 6

3.3 Ignition System 6

3.4 Chain Lubrication 6

3.5 Tightening Torquese 7

4. Troubleshooting 9

4.1 Clutch 9

4.2 Chain Drive, Chain Brake, Chain Tensioner 10

4.3 Chain Lubrication 11

4.4 Rewind Starter 12

4.5 Ignition System 13

4.6 Carburetor 15

4.7 Engine 18

5. Cutting Attachment 19

5.1 Chain Catcher 19

6. Clutch 20

6.1 Clutch Drum 22

7. Chain Brake 23

7.1 Checking Operation 23

7.2 Removing and Installing the Brake Band 23

7.3 Brake Lever 25

7.4 Cam Lever 26

7.5 Pins 27

7.6 Side Chain Tensioner 28

7.6.1 Front Chain Tensioner 29

7.6.2 Quick Chain Tensioner 29

7.7 Bar Mounting Studs 30

8. Engine 31

8.1 Muffler / Spark Arresting Screen 31

8.2 Leakage Test 32

8.2.1 Preparations 33

8.2.2 Vacuum Test 34

8.2.3 Pressure Test 34

8.3 Oil Seals 35

8.4 Removing and Installing the Shroud 36

8.5 Cylinder 37

8.6 Crankshaft 40

8.6.1 Removing and Installing 40

8.6.2 Bearings / Crankcase 45

8.7 Piston 47

8.7.1 Removal 47

8.7.2 Installing 48

8.8 Piston Rings 49

8.9 Decompression Valve 50

9. Ignition System 51

9.1 Ignition Timing 51

9.2 Ignition Module 51

9.2.1 Removing and Installing 51

9.3 Testing the Ignition Module 54

9.4 Spark Plug Boot / Ignition Lead 55

9.5 Flywheel 56

9.6 Short Circuit Wire 57

9.6.1 Testing 57

9.6.2 Removing and Installing 57

9.6.3 Ground Wire 60

9.7 Ignition System Troubleshooting 61

10. Rewind Starter 64

10.1 General 64

10.2 Removing and Installing 64

10.3 Pawl 64

10.4 Rope Rotor 65

10.5 Starter Rope / Grip 66

10.6 Tensioning the Rewind Spring 67

10.7 Replacing the Rewind Spring 68

11. Servicing the AV System 70

11.1 Annular Buffer on Chain Catcher 70

11.2 Annular Buffer at Clutch Side 70

11.3 Annular Buffer at Ignition Side 71

11.4 Stop Buffer 72

11.5 Handlebar 72

11.6 Handlebar with Handle Heating 73

12. Control Levers 76

12.1 Switch Shaft 76

12.1.1 Removing and Installing 76

12.2 Throttle Trigger/Interlock Lever 77

13. Chain Lubrication 80

13.1 Pickup Body 80

13.2 Oil Suction Hose 80

13.3 Oil Delivery Hose 81

13.4 Non-Adjustable Oil Pump 81

13.5 Adjustable Oil Pump 82

13.6 Valve 83

14. Fuel System 85

14.1 Air Filter 85

14.2 Removing and Installing the Carburetor 85

14.3 Leakage Test 86

14.4 Servicing the Carburetor 87

14.4.1 Inlet Needle 89

14.4.2 Fixed Jet 89

14.4.3 Pump Diaphragm 90

14.4.4 Choke Shaft / Choke Shutter 91

14.4.5 Adjusting Screws 91

14.5 Adjusting the Carburetor 92

14.5.1 Basic Setting 92

14.5.2 Standard Setting 93

1MS 240, MS 260, MS 260 C

Page 3

Contents

14.6 Throttle Rod 94

14.6.1 Removing and Installing the Intake Manifold 94

14.6.2 Impulse Hose 96

14.7 Tank Vent 96

14.7.1 Testing 96

14.7.2 Removing and Installing 97

14.8 Fuel Intake 98

14.8.1 Pickup Body 98

14.8.2 Fuel Suction Hose 98

14.8.3 Removing and Installing the Tank Housing 99

15. Heating System 100

15.1 Carburetor Heating 100

15.1.1 Testing the Complete System 100

15.1.2 Testing the Heating Element 100

15.1.3 Thermostatic Switch 101

15.2 Carburetor Heating System Troubleshooting Chart 103

15.3 Handle Heating System 104

15.3.1 Troubleshooting 104

15.4 Removing and Installing the Heater Switch 104

15.4.1 Heater Switch Ground Wire 105

15.5 Removing and Installing Heating Element in Rear Handle 106

15.6 Removing and Installing the Heating Element in the Handlebar 108

15.7 Removing and Installing the Generator 108

15.7.1 Handle Heating and Generator Troubleshooting Chart 110

15.7.2 Test Connections and Test Values 112

15.8 Wiring Harness 114

16. Special Servicing Tools 116

17. Servicing Aids 118

2 MS 240, MS 260, MS 260 C

Page 4

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 troubleshooting charts for all assemblies and systems in this manual and the "STIHL Service Training System".

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

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:

: = 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

aDirection of movement

219RA000 TG

Servicing and repairs are made considerably easier if the machine is mounted to assembly stand (3) 5910 890 3100. To do this, secure the mounting plate (2) 5910 850 1650 to the assembly stand with two screws (1) and washers.

The screws must not project since they, depending on the machine, may damage housings when the machine is clamped in position.

The above operation is not necessary with the new assembly stand 5910 890 3101 since the mounting plate is already fitted.

@ 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.

3MS 240, MS 260, MS 260 C

Page 5

Engage the bar mounting studs in the outer bores in the mounting plate and secure the saw in position with the nuts (arrows).

The chain sprocket cover and cutting attachment have to be removed before mounting the saw to the assembly stand – pull the hand guard toward the handlebar.

Versions with Quick Chain Tensioner

165RA000 TG

165RA468 TG

There is only one bar stud on these versions. It is pushed through the upper hole (arrow) in the mounting plate and secured with the nut (1).

The machine is held in position on the mounting plate by the screw heads on the crankcase.

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.

4 MS 240, MS 260, MS 260 C

Page 6

2. Safety Precautions

If the power tool is started up in the course of repairs or maintenance work, observe all local and countryspecific safety regulations as well as the safety precautions and warnings in the instruction manual.

Gasoline is an extremely flammable fuel and can be explosive in certain conditions.

Always wear suitable protective gloves for operations in which components are heated for assembly or disassembly.

Improper handling may result in burns or other serious injuries.

Do not smoke or bring any fire, flame or other source of heat near the fuel. All work with fuel must be performed outdoors only. Spilled fuel must be wiped away immediately.

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

5MS 240, MS 260, MS 260 C

Page 7

3. Specifications

3.1 Engine

MS 240 MS 260, MS 260 C

Displacement: 41.6 cm

50.2 cm

Bore: 42 mm 44.7 mm Stroke: 30 mm 32 mm Engine power to ISO 7293: 2.1 kW (2.85 bhp)

at 9500 rpm

2.6 kW (3.5 bhp) at 9500 rpm

Maximum permissible engine speed (with bar and chain): 13000 rpm 14000 rpm

Versions with catalytic converter Maximum permissible engine speed

13000 rpm

(with bar and chain): Idle speed: 2800 rpm 2800 rpm Clutch: Centrifugal clutch without

linings

Centrifugal clutch without

linings Clutch engages at: 3600 rpm 3600 rpm Crankcase leakage test at gauge pressure: 0.5 bar under vacuum: 0.5 bar

3.2 Fuel System

Carburetor leakage test at

0.8 bar

gauge pressure: Operation of tank vent at

0.5 bar

gauge pressure: Fuel: as specified in instruction

manual

3.3 Ignition System

Air gap between ignition module and fanwheel: 0.15...0.30 mm

Spark plug (suppressed): NGK BPMR 7 A Electrode gap: 0.5 mm

3.4 Chain Lubrication

Speed-controlled oil pump with reciprocating piston and manual flow control

Oil pump without adjustable delivery rate:

Oil pump with adjustable delivery rate:

7.5 (+/- 2.5) cm

10000 rpm

4.5...11.5 cm

10000 rpm

/min at

6 MS 240, MS 260, MS 260 C

Page 8

3.5 Tightening Torquese

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

Fastener Thread size For component Torque

Countersunk screw P 4x12 Cover plate/sprocket cover (quick chain

tensioner) Screw M 4x8 Cover plate/chain tensioner 3.0 4) Collar screw M 8x21.5 Bar mounting 23.0 1) Collar screw M10/M 8 Bar mounting/quick chain tensioner 30.0 1) Screw M 4x12 Cover, chain brake/crankcase 3.0 4) M 10x1 Decompression valve (MS 260) 14.0 Screw B 4.9x9.5 Spark arresting screen/muffler 2.0 Screw M 3.5x12 Generator/crankcase 2.0 1) Screw P 6x32.5 Handlebar, top (polymer)/tank housing 5.0 Screw P 6x21.5 Handlebar, bottom (polymer)/tank housing 5.0 Screw P 6x19 Handlebar, top and bottom/tank housing

(version with handle heating) Screw P 4x19 Handle molding 1.6 Screw M 5x12 Retaining plate/annular buffer 8.0 4) Screw M 4x16 Hand guard/crankcase (micro-encapsulated) 4.0 4) Nut M 5 Slotted nut, shroud/stud, cylinder 3.5 Screw P 6x19 Chain catcher/plug 2.8 Screw M 5x12 Spiked bumper

(with self-locking nut) 7.5 Screw M 5x20 Crankcase 9.0 Collar nut M 5 Air filter/tank housing 2.0 Screw M 4x16 Fan housing 4.0 4) M 12x1L Carrier (clutch) 50.0 Screw M 4x12 Oil pump/crankcase 3.0 4) Screw P 6x26.5 Annular buffer, tank housing/crankcase

(ignition side) Screw M 5x12 Annular buffer plate/crankcase (ignition side) 8.0 4) Screw P 6x19 Annular buffer, tank housing/crankcase

(clutch side) Screw M 5x16 Muffler/crankcase/cylinder

(version with catalytic converter and MS 260)

2.5

7.0

5.0

5.5

10.0 1), 4)

Letter

7MS 240, MS 260, MS 260 C

Page 9

Fastener Thread size For component Torque

Screw M 5x12 Muffler/crankcase/cylinder (MS 240) 10.0 1), 4) Nut M 8x1 Flywheel 33.0 3) Screw M 4x8 Side plate/crankcase 3.0 4) Screw M 4x16 Side plate/crankcase (quick chain tensioner) 3.0 Screw M 3x20 Clamp/manifold 0.5

M 5x8.5 Stud/cylinder 1.4 2) Nut M 5 Carburetor 3.5 Screw M 5x20 Cylinder/crankcase 11.0 2), 4) M 14x1.25 Spark plug 25.0 Screw M 5x20 Ignition module/crankcase (micro-

encapsulated)

Remarks:

1) Loctite 242 or 243, medium strength

2) Loctite 270, high strength

3) Degrease crankshaft/flywheel and mount oil-free

4) Screws with binding head

7.0 4)

Remarks

Use the following procedure when refitting a DG or P screw in an existing thread:

Place the screw in the hole and rotate it counterclockwise until it drops down slightly. Tighten the screw clockwise to the specified torque.

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

Coat micro-encapsulated screws with medium strength Loctite 242 or 243 before reinstalling.

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.

8 MS 240, MS 260, MS 260 C

Page 10

4. Troubleshooting

4.1 Clutch

Condition Cause Remedy

Saw chain stops under load at full throttle

Saw chain rotates at idle speed Engine idle speed too high Readjust with idle speed screw LA

Loud noises Clutch springs stretched or fatigued Replace all clutch springs

Clutch shoes badly worn Install new clutch

Clutch drum badly worn Install new clutch drum

(counterclockwise)

Clutch springs stretched or fatigued Replace the clutch springs or install

new clutch

Clutch spring hooks broken Replace the clutch springs

Needle cage damaged Fit new needle cage

Clutch shoe retainer broken Fit new retainer

Clutch shoes and carrier worn Install new clutch

9MS 240, MS 260, MS 260 C

Page 11

4.2 Chain Drive, Chain Brake, Chain Tensioner

Condition Cause Remedy

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

Wrong chain pitch Fit chain of correct pitch

Insufficient chain lubrication Check chain lubrication

Chain sprocket worn Fit new chain sprocket

Saw chain stops under load at full throttle

Saw chain rotates at idle speed Engine idle speed too high Readjust with idle speed screw LA

Saw chain does not stop immediately when brake is activated

Clutch shoes badly worn Install new clutch

Clutch drum badly worn Install new clutch drum

Brake band blocked Check freedom of movement and

operation of brake band

(counterclockwise)

Clutch springs stretched or fatigued Replace the clutch springs or install

new clutch

Clutch spring hooks broken Replace the clutch springs

Brake spring stretched or broken Fit new brake spring

Brake band stretched or worn Fit new brake band

Clutch drum worn Install new clutch drum

10 MS 240, MS 260, MS 260 C

Page 12

4.3 Chain Lubrication

In the event of trouble with the chain lubrication system, check and rectify other sources of faults before disassembling the oil pump.

Condition Cause Remedy

Chain receives no oil Oil tank empty Fill up with oil and check setting of

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

oil pump if necessary

Intake hose or pickup body clogged or intake hose ruptured

Valve in oil tank blocked Clean or replace valve

Teeth on worm worn Install new worm

Oil pump damaged or worn Install new oil pump

Machine losing chain oil Oil pump body damaged Install new oil pump

Oil pump damaged or worn Install new oil pump

Oil suction hose connection damaged

Oil pump delivers insufficient oil Oil pump worn Install new oil pump

Oil pump delivery rate set too low Adjust oil pump

Fit new intake hose and pickup body

Install new oil intake hose

(only on version with adjustable oil pump)

11MS 240, MS 260, MS 260 C

Page 13

4.4 Rewind Starter

Condition Cause Remedy

Starter rope broken Rope pulled out too vigorously as

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

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

Rewind spring broken Fit new rewind spring

Starter rope cannot be pulled out far enough

Starter rope can be pulled out almost without resistance (crankshaft does not turn)

Spring overtensioned Check rewind spring and reduce

Guide peg on pawl or pawl itself is worn

Fit new starter rope

tension

Fit new pawl

Starter rope is difficult to pull or rewinds very slowly

Spring clip on pawl fatigued Fit new spring clip

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)

Decompression valve is not open Open, check and replace

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

decompression valve if necessary

12 MS 240, MS 260, MS 260 C

Page 14

4.5 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. If sooting keeps recurring, check air filter

Ignition lead loose in ignition module

Fuel/oil mixture – too much oil

Incorrect air gap between ignition module and flywheel

Flywheel cracked or has other damage or pole shoes have turned blue

Ignition timing wrong, flywheel out of adjustment, key in flywheel has sheared off

Secure ignition lead properly

Use correct mixture of fuel and oil

Set air gap correctly

Install new flywheel

Fit key if necessary and secure flywheel properly or install new flywheel

Weak magnetization in flywheel Install new flywheel

Irregular spark Check operation of switch shaft/

contact springs 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.

Crankcase damaged (cracks) Install new crankcase

13MS 240, MS 260, MS 260 C

Page 15

Condition Cause Remedy

No spark Spark plug faulty Install new spark plug

Faulty insulation or short in short circuit wire

Break in ignition lead or insulation damaged

Ignition module faulty Install new ignition module

Check short circuit wire for short circuit to ground

Check ignition lead and replace if necessary

14 MS 240, MS 260, MS 260 C

Page 16

4.6 Carburetor

Condition Cause Remedy

Carburetor floods; engine stalls Inlet needle not sealing

– foreign matter in valve seat or cone

Inlet control lever sticking on spindle

Helical spring not located on nipple of inlet control lever

Perforated disc on diaphragm is deformed and presses constantly against the inlet control lever

Metered diaphragm deformed Fit a new metering diaphragm

Poor acceleration Setting of low speed screw too lean Check basic carburetor setting,

Setting of high speed screw too lean

Remove and clean the inlet needle, clean the carburetor

Check inlet control lever, replace if necessary

Remove the inlet control lever and refit it correctly

Fit a new metering diaphragm

correct if necessary

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

Impulse hose damaged or kinked Install new impulse hose

Tank vent faulty Replace tank vent

Leak on fuel hose from tank to carburetor

Fit a new metering diaphragm

Seal connections or install new fuel hose

15MS 240, MS 260, MS 260 C

Page 17

Condition Cause Remedy

Engine will not idle, idle speed too high

Engine stalls at idle speed Idle jet bores

Throttle shutter opened too wide by idle speed screw LA

Oil seals/crankcase leaking Seal or replace oil seals/crankcase

or ports blocked

Setting of low speed screw too rich or too lean

Setting of idle speed screw LA incorrect – throttle shutter completely closed

Tank vent faulty Replace tank vent

Leak on fuel hose from tank to carburetor

Reset idle speed screw LA correctly

Clean the carburetor

Reset low speed screw L correctly

Reset idle speed screw LA correctly

Seal connections or install new fuel hose

16 MS 240, MS 260, MS 260 C

Page 18

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 and rod

Tank vent faulty Replace tank vent

Fuel pickup body dirty Install new pickup body

Fuel strainer dirty Clean fuel strainer in carburetor,

replace if necessary

Leak on fuel hose from tank to carburetor

Setting of high speed screw H too rich

Main jet bores or ports blocked Clean the carburetor

Seal connections or install new fuel hose

Check basic carburetor setting, correct if necessary

Pump diaphragm damaged or fatigued

Impulse hose damaged or kinked Install new impulse hose

Ignition timing wrong, flywheel out of adjustment, key in flywheel is missing or has sheared off

Fit new pump diaphragm

Fit key if necessary and secure flywheel properly or install new flywheel

17MS 240, MS 260, MS 260 C

Page 19

4.7 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

Engine does not deliver full power or runs erratically

Oil seals in crankcase damaged Replace the oil seals

Crankcase leaking or damaged (cracks)

Piston rings worn or broken Fit new piston rings

Muffler / spark arresting screen carbonized

Air filter dirty Replace air filter

Fuel/impulse hose severely kinked or damaged

Decompression valve is not closed Close, check and replace

Seal or replace the crankcase

Clean the muffler (inlet and exhaust), replace spark arresting screen, replace muffler if necessary

Fit new hoses or position them free from kinks

decompression valve if necessary

Engine overheating Insufficient cylinder cooling. Air

inlets in fan housing blocked or cooling fins on cylinder very dirty

18 MS 240, MS 260, MS 260 C

Thoroughly clean all cooling air openings and the cylinder fins

Page 20

5. Cutting Attachment

Wear gloves to protect your hands from injury.

: Unscrew the hex nuts (1).

: Remove the chain sprocket

cover (2).

: Remove the guide bar (3) with

chain.

– Reassemble in the reverse

sequence.

165RA002 TG

: Carefully pry the wing nut (1) out

of the sprocket cover (arrow).

– Check the wing nut (1) and

replace if necessary

When installing the adjusting wheel, make sure its teeth point inboard.

– Reassemble in the reverse

sequence.

5.1 Chain Catcher

165RA469 TG

– Remove the sprocket cover and

cutting attachment, b 5

165RA247 TG

Versions with Quick Chain Tensioner

Wear gloves to protect your hands from injury.

: Swing the wing nut (1) upright

and loosen it counterclockwise.

: Remove the sprocket cover (2)

and tensioning gear (3) with guide bar (4).

– Swing the wing nut (1) upright.

: Push the wing nut (1), thin side

first (see arrow), into the opening and press it down until it snaps into positon.

165RA464 TG

: Take out the screw (arrow).

: Take out the screw (arrow) and

remove the chain catcher (1).

165RA007 TG

– Reassemble in the reverse

sequence.

– Tightening torques, b 3.5

165RA455 TG

– Reassemble in the reverse

sequence.

– Remove the cover plate (1) and

adjusting wheel (2).

19MS 240, MS 260, MS 260 C

Page 21

6. Clutch

– Troubleshooting, b 4.1

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the clutch drum, b 6.1

– Remove the air filter, b 14.1

– Remove the shroud, b 8.4

: Pull boot (1) off the spark plug.

: Push the locking strip (1)

0000 893 5903 into the cylinder so that "OBEN-TOP" is visible.

165RA009 TG

165RA011 TG

– Pull the clutch shoes off the

carrier.

: Remove the retainers (1).

165RA014 TG

: Unscrew the spark plug (1).

: Unscrew the clutch (1).

Note that the clutch has a left-hand thread.

165RA010 TG

Disassembling

: Use hook (2) 5910 890 2800 to

remove the clutch springs (1).

165RA012 TG

– Clean all parts..

– Replace any damaged parts.

165RA013 TG

: Fit the retainers (1).

165RA015 TG

165RA016 TG

20 MS 240, MS 260, MS 260 C

Page 22

: Fit the clutch shoes (2) over the

arms (2).

: Clamp the clutch in a vise

(arrow).

165RA017 TG

: Check the clutch – all springs

(arrows) must be properly attached.

TOP

165RA018 TG

– Make sure the washer (1) is in

place.

Installed position is correct when "TOP" (arrow) faces outwards.

165RA020 TG

: Screw the clutch (1) on to the

crankshaft stub and tighten down the hexagon (arrow) firmly – lefthand thread.

– Tightening torques, b 3.5

– Remove the locking strip from the

cylinder.

– Reassemble all other parts in the

reverse sequence.

165RA021 TG

165RA023 TG

Attach the springs on the side with the raised hexagon (arrow).

: Attach one end of each spring (1)

to the clutch shoes.

: Use the hook (2) 5910 890 2800

to attach the other ends of the springs and press them firmly into the clutch shoes.

TOP

165RA470 TG

165RA022 TG

: Position the clutch on the

crankshaft stub so that the raised hexagon (arrow) faces outwards.

21MS 240, MS 260, MS 260 C

Page 23

6.1 Clutch Drum

– Remove the sprocket cover and

cutting attachment, b 5

: Pull the hand guard (1) towards

the handlebar.

Remove and install the clutch drum (1), see instruction manual.

: Pull off the needle cage (1).

165RA024 TG

– Clean the needle cage (1) and

crankshaft stub, b 17

– Lubricate the needle cage (1) and

crankshaft stub, b 17

165RA377 TG

80%

– Inspect the clutch drum (1) for

signs of wear.

100%

165RA411 TG

The notch (arrow) in the clutch drum must engage the worm gear's driver (1).

Use the mark (2) for orientation.

– Apply thin coating of oil to outside

diameter of clutch drum and the brake band.

– Reassemble all other parts in the

reverse sequence.

165RA029 TG

165RA415 TG

If there are signs of serious wear on the inside diameter of the clutch drum (1), check the remaining wall thickness. If it is less than about 80% of the original thickness, install a new clutch drum.

22 MS 240, MS 260, MS 260 C

Page 24

7. Chain Brake

7.1 Checking Operation

The chain brake is one of the most important safety devices on the chain saw. Its efficiency is measured in terms of the chain braking time, i.e. the time that elapses between activating the brake and the saw chain coming to a complete standstill.

Contamination (with chain oil, chips, fine particles of abrasion, etc.) and smoothing of the friction surfaces of the brake band and clutch drum impair the coefficient of friction, which prolongs the braking time. A fatigued or stretched brake spring has the same negative effect.

– Start the engine.

– With the chain brake activated

(locked), open the throttle wide for a brief period (max. 3 seconds) – the chain must not rotate.

7.2 Removing and Installing the Brake Band

: Disengage the chain brake by

pulling the hand guard (1) towards the front handle.

The brake band is no longer under tension.

– Remove the clutch drum, b 6.1

Versions with Quick Chain Tensioner

165RA024 TG

: Take out the screw (arrow) and

remove the side plate (1).

: Remove the upper bumper strip

(2).

165RA037 TG

– With the chain brake released,

open the throttle wide and activate the brake manually – the chain must come to an abrupt stop.

The braking time is in order if deceleration of the saw chain (less than a second) is imperceptible to the eye.

The chain must come to a standstill in less than a second.

If the chain brake does not operate properly, refer to troubleshooting, b 4.2.

– Troubleshooting, b 4.2

– Remove the sprocket cover and

cutting attachment, b 5

: Take out the screw (arrow) and

remove the side plate (1).

: Take out the screws (arrows).

165RA471 TG

On versions with handle heating

– Remove the ground wire,

b 15.4.1.

165RA038 TG

165RA039 TG

: Remove the cover (1).

23MS 240, MS 260, MS 260 C

Page 25

: Pry the brake band (1) out of its

seat (arrow).

– Remove the brake band (1).

Do not over-stretch the brake band.

: Turn the brake band (1) to one

side and disconnect it from the brake lever (arrow).

165RA040 TG

: Hold the brake band (1)

sideways, attach it to the brake lever (arrow) and then swing it in the direction of its seat.

: Position the brake band (1) it the

165RA042 TG165RA043 TG

guide (arrow) first.

165RA044 TG

: Push the brake band (1) into its

guide (arrow) as far as stop.

: Place the cover (1) in position.

165RA045 TG

– On versions with handle heating,

fit the ground wire, b 15.4.1

– Insert screws and tighten them

down firmly.

165RA040 TG

165RA039 TG

– Tightening torques, b 3.5

– On versions with quick chain

tensioner, install the upper bumper strip.

– Install the clutch drum,

165RA041 TG

b 6.1

: Push the brake band (1) into its

seat.

Install a new brake band if there are noticeable signs of wear (large areas on inside diameter and/or parts of outside diameter – arrows) and its remaining thickness is less than 0.6 mm.

24 MS 240, MS 260, MS 260 C

– Check operation.

– Reassemble all other parts in the

reverse sequence.

Page 26

7.3 Brake Lever

– Troubleshooting, b 4.2

– Push the hand guard towards the

guide bar.

The brake spring (1) is now relaxed.

– Remove the brake band, b 7.2

: Use the assembly tool 117 890

0900 to disconnect the brake spring (1) from the anchor pin (arrow).

– Disconnect the brake spring (1)

from the brake lever.

: Remove the E-clip (arrow).

165RA047 TG

: Pull the hand guard (1) and brake

lever (2) off the pivot pins (arrows) together.

– Remove the hand guard (1) and

brake lever (2).

165RA049 TG

– Inspect the pivot pins and replace

if necessary, b 7.5

– Inspect the cam lever and

replace if necessary, b 7.4

Clean all disassembled parts with a

little standard commercial solventbased degreasant containing no chlorinated or halogenated hydrocarbons.

165RA050 TG

– Hold the brake lever (1) so that

the brake spring attachment point (arrow) is at the top.

: Push the brake lever (1) into the

hand guard recess and line up the holes.

165RA052 TG

: Take out the screw (arrow).

165RA048 TG

: Take the brake lever (2) out of the

hand guard (1).

– Inspect the brake lever (2) and

hand guard (1) and replace if necessary.

165RA051 TG

: Push the hand guard with brake

lever over the machine until it is positioned against the pivot pin.

165RA472 TG

25MS 240, MS 260, MS 260 C

Page 27

: Lift the bearing boss of the hand

guard and the brake lever a little and position them over the pivot pins (arrows).

: Turn the cam lever (1) to one side

until the cam of the hand guard (arrow) slips passed it.

– Push the hand guard bearing

boss and the brake lever on to the pivot pins.

165RA054 TG165RA055 TG

: The turns of brake spring must be

tightly against one another in the relaxed condition. If this is not the case, replace the brake spring.

Check the correct position of the protective hose – it must be centered in the spring.

a = 20 mm

If the groove in the brake spring anchor pin is worn, install a new pin, b 7.5

165RA057 TG

: Use the assembly tool (2)

1117 890 0900 to attach the brake spring (1) to the anchor pin (arrow).

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

– Lubricate the brake lever, b 17

7.4 Cam Lever

The cam lever defines the locked position of the hand guard.

– Remove the brake lever, b 7.3

165RA059 TG

165RA058 TG

: Fit the E-clip (1).

26 MS 240, MS 260, MS 260 C

: Attach the brake spring (1) to the

brake lever (arrow).

: Disconnect the spring (1) from

the anchor pin (arrow).

165RA056 TG

165RA060 TG

Page 28

The anchor pins secure the springs. Worn pins must be replaced – the springs may otherwise become detached and pop out.

All parts have been removed from the pins in the following illustrations

7.5 Pins

165RA061 TG

for greater clarity.

165RA064 TG

: Remove the E-clip (arrow).

– Pull the cam lever (1) off the pivot

pin.

– Check the cam lever (1) and

spring (2) and replace if necessary.

– Check the condition of the cam

contour (arrow) and replace the hand guard if necessary.

: Fit the E-clip (1).

: Attach the spring (1) to the cam

lever so that the open side of the

165RA062 TG

spring hook (Pfeil) points toward the housing.

If the groove in the spring's anchor pin is worn, install a new pin, b 7.5

– Attach the spring (1) to the anchir

pin (2).

: Use a suitable tool to pull out the

165RA065 TG

pins (arrows).

165RA066 TG

– Position the cam lever (1) so that

its cam (arow) faces the cam on the hand guard.

: Push the cam lever (1) on to the

pivot pin (2).

The cam lever is not yet under tension – the spring may become detached.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

– Lubricate the cam lever, b 17

165RA063 TG

165RA067 TG

– Before installing the new pin (1),

coat its knurled shank with Loctite, b 17

: Position the new pin (1) in the

bore (arrow) so that the knurling on the pin meshes with the existing knurling in the bore.

Turn the pin (1) back and forth as necessary.

27MS 240, MS 260, MS 260 C

Page 29

7.6 Side Chain Tensioner

– Remove the sprocket cover and

cutting attachment, b 5

– Troubleshooting, b 4.2

: Drive home the pins (1 and 2) as

shown in the illustrations.

: Carefully tap home the pins to

obtain the following dimensions: Pin (1) a = 4.3 – 4.7 mm Pin (2) b =. 3.0 – 3.4 mm

165RA068 TG

: Carefully tap home the pins to

obtain the following dimensions: Pin (3) a = 4.3 – 4.7 mm Pin (4) b = 3.0 – 3.4 mm Pin (5) = 3.0 – 3.4 mm

The pins must be driven home squarely.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA069 TG165RA070 TG

– Lubricate the brake and cam

levers, b 17

165RA378 TG

– Remove the side plate.

: Turn the spur gear (2) clockwise

until the tensioner slide (1) butts against the right-hand end and the screw (arrow) is visible.

165RA459 TG

: Drive home pins (3, 4 and 5) as

specified below.

28 MS 240, MS 260, MS 260 C

: Take out the screw (arrow).

– Pull out the tensioner side with

adjusting screw, thrust pad and spur gear.

165RA460 TG

Page 30

7.6.1 Front Chain Tensioner

– Remove the sprocket cover and

cutting attachment, b 5

– Troubleshooting, b 4.2

– Remove the side plate, b 7.2

: Inspect the thrust pad (1),

adjusting screw (2), tensioner slide (3), cover plate (4), spur gear (5) and O-ring (6) and replace as necessary.

: Fit the O-ring in the spur gear

recess (arrow).

– Clean all disassembled parts with

a little standard commercial solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

Always replace the adjusting screw and spur gear as a matching pair.

165RA461 TG

: Turn the adjusting screw (1)

clockwise until the tensioner slide (2) butts against the right-hand end and the screw (arrow) is visible.

165RA458 TG

: Pull out the tensioner slide (2)

with thrust pad (3).

: Pull off the thrust pad (1) and

unscrew the adjusting screw (2) from the tensioner slide (3).

– Check the individual parts and

replace if necessary.

– Reassemble in the reverse

sequence.

165RA465 TG

– Clean all disassembled parts with

a little standard commercial solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

– Lubricate thread with STIHL

multipurpose grease, b 17

– Reassemble all other parts in the

reverse sequence.

7.6.2 Quick Chain Tensioner

The quick chain tensioner is installed in the chain sprocket cover. See chapter on cutting attachment, b 5

165RA463 TG

– Lubricate the threads, gears and

O-ring with STIHL multipurpose grease, b 17

– Reassemble in the reverse

sequence.

29MS 240, MS 260, MS 260 C

Page 31

7.7 Bar Mounting Studs

Versions with Quick Chain Tensioner

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the side plate, b 7.6

: Push stud puller 5910 893 0501

(1) over the collar studs (arrows) as far as it will go and unscrew the studs counterclockwise.

: Before installing, coat threads

(arrow) of collar studs with Loctite, b 17

165RA081 TG

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the side plate, b 7.6

: Push stud puller 5910 893 0501

(1) over the collar stud (arrow) as far as it will go and unscrew the stud counterclockwise.

165RA082 TG

: Before installing, coat thread

(arrow) of collar stud with Loctite, b 17

165RA083 TG

165RA087 TG

– Fit collar studs and tighten them

down firmly.

– Tightening torques, b 3.5

– Reassemble all other parts in the

reverse sequence.

– Fit collar stud and tighten it down

firmly.

– Tightening torques, b 3.5

Reassemble all other parts in the reverse sequence.

30 MS 240, MS 260, MS 260 C

Page 32

8. Engine

8.1 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 4

: Take out the screws (arrows).

: Remove the heat shield (1), if

fitted.

: Remove the gasket (2).

Spark arresting screen

(if fitted)

165RA084 TG

165RA086 TG

: Check the reflector foil (1), if

fitted, and replace if necessary

165RA457 TG

– Remove the exhaust casing (1).

: Take out the screws (arrows).

– Remove the muffler (1), check

and replace if necessary.

: Take out the screw (1).

: Pull out the spark arresting

screen (2).

– Clean the spark arresting screen

165RA085 TG

(2) or replace if necessary.

– Reassemble in the reverse

sequence.

: Position the reflector foil (1)

aganst the edges (arrows).

165RA473 TG

– Hold the machine upright.

: Inspect and clean the sealing

faces (arrows) and remove any gasket residue.

165RA090 TG

165RA091 TG

31MS 240, MS 260, MS 260 C

Page 33

: Place the heat shield (1) in

position (if fitted) and use the indentations (arrows) to line it up on the sealing face of the cylinder exhaust port.

: If the heat shield is fitted, position

the gasket (1) between the projections (arrows) – the gasket is now held in position.

– Versions without heat shield:

Place gasket (1) on the cylinder exhaust port, the raised edge must face the port and the holes must be in alignment.

165RA092 TG

– Carefully place the muffler (1) in

position.

: Line up the screws (arrows) and

check the position of the gasket.

: Insert screws (2) to hold the

muffler in position.

: Insert screws (arrows) and

tighten them down firmly.

165RA093 TG

– Remove the screws used to hold

the muffler in position.

: Attach tab (arrow) of the exhaust

casing (1) to the muffler first and then swing it into position.

165RA094 TG

: Insert screws (arrows) and

tighten them down firmly.

– Tightening torques, b 3.5

8.2 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.

165RA095 TG

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.

165RA084 TG

32 MS 240, MS 260, MS 260 C

Page 34

8.2.1 Preparations

– Remove the shroud, b 8.4

– Set the piston to top dead center.

This can be checked through the spark plug hole.

– Remove the decompression

valve, b 8.9

: Fit the plug (1) 1122 025 2200

and tighten it firmly.

: Fit the spark plug (2) and tighten

it down firmly.

– Tightening torques, b 3.5

: Fit the sealing plate (1)

165RA474 TG

0000 855 8106 between the cylinder exhaust port and heat shield (if fitted) and tighten down the screws moderately.

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

– Remove the carburetor, b 14.2

165RA099 TG

– Pin (1) must be in the test flange

1128 850 4200 – it seals the impulse hose.

: Make sure that the pin (1) is in

hole "2" (arrow).

– Fit the test flange 1128 850

4200 (1).

165RA475 TG

165RA493 TG165RA494 TG

– Remove the muffler exhaust

casing, b 8.1

: Loosen the screws (arrows).

: Check that the sleeve (2) and

washer (1) are in place.

165RA085 TG

165RA100 TG

: When pushing the test flange (1)

into position, make sure the pin engages the impulse hose (arrow).

: Fit the nuts (arrows) and tighten

them down firmly.

33MS 240, MS 260, MS 260 C

Page 35

8.2.2 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.

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 8.3.

– After finishing the test, push the

ring (1) to the right to vent the pump.

– Continue with pressure test,

b 8.2.3

8.2.3 Pressure Test

165RA104 TG

: 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 crankcase is airtight.

– If the pressure drops, the leak

must be located and the faulty part replaced.

165RA003 TG

: Connect suction hose (1) of

pump 0000 850 1300 to nipple (arrow).

: Push ring (1) to the left.

: Operate the lever (2) until the

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

Carry out the same preparations as for the vacuum test, b 8.2.2

– Always carry out the vacuum test,

before the pressure test, b 8.2.2

: Connect pressure hose (1) of

165RA476 TG

pump 0000 850 1300 to nipple (arrow).

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

– After finishing the test, push the

ring (1) to the left to vent the

165RA104 TG

pump – disconnect the hose.

– Remove the test flange.

– Install the carburetor, b 14.2

– Loosen the muffler and pull out

the sealing plate.

– Tighten down the muffler firmly.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

34 MS 240, MS 260, MS 260 C

Page 36

8.3 Oil Seals

– Clamp the puller arms.

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

Ignition side

– Remove the fan housing,

b 10.2

– Remove the flywheel, b 9.5

– Remove the generator, b 15.7

Versions with handle hearing

: Remove the Woodruff key (1).

– Pull out the oil seal.

Take care not to damage the crankshaft stub.

– Clean the sealing face with a little

standard solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

– Lubricate sealing lips of new oil

seal with grease, b 17

165RA106 TG

– Apply a thin coating of sealant to

the outside diameter of the oil seal (1), b 17

: Install the Woodruff key (1) – its

straight side (arrow) must be in line with the taper.

– Reassemble all other parts in the

reverse sequence.

Clutch side

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the clutch, b 6

– Remove the oil pump,

adjustable, b 13.5,

165RA108 TG

non-adjustable, b 13.4

165RA109 TG

– Free off the oil seal in its seat by

tapping it with a suitable tube or a punch.

: Apply puller (1) 5910 890 4400

with No. 3.1 jaws 0000 893 3706.

– Slip the oil seal (1), open side

facing the crankcase, over the crankshaft stub.

: Use press sleeve (2)

1121 893 2400 to install the oil seal (1).

165RA107 TG

The seating face must be flat and free from burrs.

– Wait about one minute, then

rotate the crankshaft several times.

Clean the crankshaft with a little standard commercial solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

165RA110 TG

: Remove the washer (1) and

ring (2).

35MS 240, MS 260, MS 260 C

Page 37

– Slip the oil seal (2), open side

facing the crankcase, over the

installing sleeve.

– Remove the installing sleeve (1).

8.4 Removing and Installing the Shroud

– Free off the oil seal in its seat by

tapping it with a suitable tube or a punch.

: Apply puller (1) 5910 890 4400

with No. 3.1 jaws 0000 893 3706.

– Clamp the puller arms.

– Pull out the oil seal.

Take care not to damage the crankshaft stub.

– Clean the sealing face with a little

standard solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

– Lubricate sealing lips of new oil

seal with grease, b 17

165RA111 TG

: Use press sleeve (2) 1120 893

2400 to install the oil seal (1).

– Wait about one minute, then

rotate the crankshaft several times.

: Unscrew the slotted nut (arrow).

165RA113 TG

: Remove the shroud (1) over the

decompression valve (2).

165RA114 TG

: Pull off the stop buffer (1), check

it and replace if necessary.

– Reassemble in the reverse

sequence.

165RA115 TG

165RA116 TG

: Fit the washer (1) and ring (2).

– Reassemble all other parts in the

reverse sequence.

165RA477 TG

: Fit the installing sleeve (1) 1118

893 4602.

– Apply a thin coating of sealant to

the outside diameter of the oil seal (2), b 17

: Push out the slotted nut (1) with

insulator.

36 MS 240, MS 260, MS 260 C

165RA004 TG

Page 38

: Pull the insulator (1) off the

slotted nut (2).

– Check the individual parts and

replace if necessary.

Versions with decompression valve

165RA005 TG

: Bond the new reflector foil in

position along the ribs (arrows).

8.5 Cylinder

Before removing the piston, decide whether or not the crankshaft has to be removed as well.

Cylinder installed

To remove the flywheel and clutch, the.crankshaft has to be blocked by inserting the locking strip in the spark plug hole.

Cylinder removed

165RA008 TG

To remove the flywheel and clutch, the crankshaft has to be blocked by resting the piston on the wooden assembly block.

– Reassemble in the reverse

sequence.

: Push the slotted nut (1) with

insulator into the bore until it engages in position.

– Check the cap (1), if fitted, and

replace if necessary

If a new shroud is fitted, the cap (1) must be removed.

165RA456 TG

: Fit the shroud (1). Push the lugs

(2) into the holes (arrows).

Make sure the stud is located against the slotted nut.

– Screw home the slotted nut as far

as stop.

– Remove the shroud, b 8.4

– Pull off the boot and unscrew the

spark plug, b 6

– Remove the fan housing,

b 10.2

– Remove the carburetor, b 14.2

– Push the manifold out of the tank

housing, b 14.6.1

– Remove the muffler, b 8.1

– Remove the decompression

165RA025 TG

valve, b 8.9

– Remove the handlebar, b 11.5.

On versions with handle heating, take out the screws and swing the handlebar to one side, b 11.6

– Inspect the reflector foil (1) and

replace it if it is damaged.

– Reassemble all other parts in the

reverse sequence.

165RA457 TG

37MS 240, MS 260, MS 260 C

Page 39

Always use a new cylinder gasket when re-installing the cylinder.

: Pull off the stop buffer (1).

: Pull the impulse hose (1) off the

nipple (arrow).

165RA116 TG

: Carefully lift the cylinder (1) away.

Do not use pointed or sharp-edged tools for this job.

165RA387 TG

: Remove the cylinder gasket (1).

165RA495 TG

165RA032 TG

– Line up the cylinder gasket (1) so

that the tabs (arrow) point toward the carburetor and cutting attachment.

: Place the cylinder gasket (1) in

position.

165RA030 TG

: Take out the four cylinder base

screws through the holes (arrows) in the cylinder.

165RA027 TG

– Inspect and clean the sealing

face (arrow), b 17

The sealing face must be in perfect condition. Always replace components with damaged sealing faces, b 4.7.

– Inspect the intake manifold (2)

and replace it if necessary – even very minor damage can result in engine running problems, b 4.7

: Loosen the hose clamp (1) and

165RA031 TG

pull off the manifold (2).

165RA033 TG

38 MS 240, MS 260, MS 260 C

Page 40

: Tighten the screw until the gap

"a" between the two ends of the hose clamp is about 5 to 6 mm.

– Push the manifold (1) on to the

intake stub.

: Line up the manifold (1)

– the tab must be pisitioned as shown in the illustration (arrow).

– Position the hose clamp so that

the screw head (arrow) points toward the clutch side.

165RA034 TG

: Inspect and clean the sealing

face (arrow) and remove any gasket residue.

– Check the sealing faces on the

cylinder intake and exhaust ports.

The sealing faces must be in perfect condition. If the sealing faces are damaged, install a new cylinder.

165RA071 TG165RA035 TG

– Lubricate the piston, piston rings

and cylinder wall with oil, b 17

: Use the clamping strap (1)

165RA072 TG165RA073 TG

0000 893 2600 to compress the rings around the piston.

– Check correct installed position

of rings, b 8.8

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

165RA074 TG

: Push the hose clamp on to the

manifold.

– Turn the hose clamp until the

screw head is below the lower cylinder fin (arrow).

: Slide the wooden assembly block

(1) 1108 893 4800 between the piston and crankcase.

165RA079 TG

: Align the cylinder so that the

intake port (arrow) points toward the rear handle.

While sliding the cylinder over the piston, hold the clamping strap tightly around the piston so that the rings do not project – they might otherwise break.

: Slide the cylinder over the piston,

the clamping strap moves downwards at the same time.

39MS 240, MS 260, MS 260 C

Page 41

remove the generator, b 15.7

– Drain the fuel and oil tanks, b 1

– On versions with handle heating,

: Remove the clamping strap (1)

and wooden assembly block (2).

Make sure the cylinder gasket is properly seated.

– Push the cylinder fully home.

: Insert the screws (arrows) to hold

the cylinder and gasket in position..

165RA080 TG

– Lift the tank housing a little.

: Push the impulse hose (1) on to

the nipple (arrow).

– Reassemble all other parts in the

reverse sequence.

8.6 Crankshaft

8.6.1 Removing and Installing

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the adjustable oil pump,

165RA027 TG

b 13.5

– Remove the non-adjustable oil

pump, b 13.4

– Remove the brake band, b 7.2

– Remove the tank housing,

b 14.8.3

Always install new bearings and oil seals after removing the crankshaft,

165RA096 TG

b 8.6.2 and b 8.3

Removing – clutch side

Use the tools in the service tool set 5910 007 2200 for removing and installing.

: Remove the washer (1) and ring

(2).

165RA110 TG

– Tighten down the screws in an

– Remove the brake lever, b 7.3

alternate pattern.

– Remove the handlebar, b 11.5

– Tightening torques, b 3.5

. Remove the handleber with handle heating, b 11. 6

– Remove the cylinder, b 8.5

– Remove the piston, b 8.7

: Take out the screws (arrows).

– Remove the flywheel, b 9.5

40 MS 240, MS 260, MS 260 C

165RA097 TG

Page 42

Versions with Quick Chain Tensioner

Removing – ignition side

Use the tools in the service tool set 5910 007 2200 for removing and installing.

: Use a 4 mm diameter drift to drive

out the cylindrical pin at the chain tensioner side.

: The tensioner slide (1) must butt

against the thrust pad (arrow).

165RA117 TG

: Push the service tool (1)

5910 890 2205 over the collar screw, fit the nut and tighten it firmly.

: Turn the spindle (2) clockwise

until the crankshaft stub is pushed out of the ball bearing.

This operation releases the clutch side of the crankcase and separates the two halves.

165RA078 TG

– Install new ball bearings and oil

seals, b 8.6.2 and b 8.3

165RA479 TG

– Unscrew the spindle (1) of

service tool 5910 890 2220 until the drilled plate (2) butts against the crankcase – left-hand thread.

: Fit the plate (2) 5910 893 2101

against the ignition side of the crankcase so that the number "6" (arrow) is at the bottom.

: Insert three M5x72 screws (3) in

the holes marked "6" and tighten them down against the drilled plate.

165RA121 TG

– Back off the spindle (1) in service

tool until it is clear of the crankshaft stub.

: Push the service tool (2)

5910 890 2205 over the collar screws, fit the nuts (arrows) and tighten them firmly.

165RA478 TG

: Remove the gasket (1).

165RA120 TG

: Turn the spindle (1)

counterclockiwse until the crankshaft is pushed out of the ignition side of the crankcase.

165RA122 TG

41MS 240, MS 260, MS 260 C

Page 43

: The crankshaft (1), connecting

rod (2) and needle bearing form an inseparable unit. Always replace as a complete unit.

– Check the two halves of the

crankcase and ball bearings and replace if necessary, b 8.6.2

Before installing, clean the crankshaft with a standard commercial, solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

Installing – ignition side

Take care not to damage the crankshaft stub.

Inspect and clean the sealing faces on the ignition side of the crankcase (including the cylinder sealing face) – the sealing faces must not be damaged in any way.

165RA123 TG

– Position the tapered stub of the

crankshaft (arrow) above the ball bearing at the ignition side.

Wear protective gloves to reduce the risk of burn injury.

– Heat the inner bearing race to

about 150°C (300°F).

: Push the crankshaft into the ball

bearing at the ignition side as far a stop.

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

165RA124 TG

If it is not possible to heat the inner bearing ring, use the drilled plate 5910 893 2102 to install the crankshaft.

: Screw the screw sleeve (1)

5910 893 2421 as far as stop onto the fully extended spindle of service tool (2) 5910 893 2101.

Coat tapered stub of crankshaft with oil.

: Position the tapered stub of the

crankshaft (arrow) above the ball bearing at the ignition side and push it home.

165RA125 TG

165RA124 TG

42 MS 240, MS 260, MS 260 C

Page 44

Installing – clutch side

Take care not to damage the crankshaft stub.

: Position the screw sleeve (2) on

the crankshaft thread and screw it into place.

– Turn the spindle (1) until the

drilled plate butts against the ignition side of the crankcase.

: Secure the drilled plate 5910 893

2101 in position by inserting three M5x72 screws (arrow) in the holes marked "6", then turn the spindle (1) clockwise.

165RA126 TG

The crankshaft turns when it is being pulled into place with the service tool. Therefore, make sure the small end of the connecting rod always points upward to the cylinder.

– Remove the service tool.

165RA127 TG

: Fit a new gasket (1) and locate it

on the pin (arrow).

Inspect and clean the sealing faces on the clutch side of the crankcase (including the cylinder sealing face) – the sealing faces must not be damaged in any way.

165RA128 TG

165RA130 TG

: Fit two M5x72 screws (arrows) in

the holes at the ignition side – to act as guides and prevent twisting.

– Coat straight stub of crankshaft

with oil.

165RA129 TG

– Install the ignition side of the

crankcase as far as stop.

: Make sure the pin (1) engages

the hole and the gasket is not pinched or twisted.

165RA132 TG

43MS 240, MS 260, MS 260 C

Page 45

– Release the crankshaft. Hold the

service tool steady and continue turning the spindle until the tool butts against the crankcase.

– Fit the sprocket cover mounting

nuts on the bar studs and screw them down finger-tight.

– Position the clutch side of the

crankcase on the straight crankshaft stub and the two screws.

Wear protective gloves to reduce the risk of burn injury.

– Heat the inner bearing race to

about 150°C (300°F).

: Push the crankcase fully home.

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

If it is not possible to heat the inner bearing ring, use the service tool 5910 007 2205 to install the crankcase.

– Coat straight stub of crankshaft

with oil.

– Position the clutch side of the

crankcase on the straight crankshaft stub and the two screws.

165RA131 TG

– Screw the spindle (left-hand

thread) fully into the service tool 5910 890 2205.

: Screw the screw sleeve (1)

5910 893 2409 omto the spindle of service tool 5910 890 2205 as far as stop (left-hand thread).

– Apply the screw sleeve to the

crankshaft stub (arrows) and push the service tool over the bar studs.

: Hold the crankshaft steady and

rotate the spindle counterclockwise to screw the screw sleeve onto the crankshaft stub.

165RA133 TG

: Turn the spindle

counterclockwise until the crankcase locates against the guide sleeves.

219RA131 TG

Make sure the pin (arrow) engages the hole and the gasket is not pinched or twisted.

165RA135 TG

165RA136 TG

– Unscrew the mounting nuts.

– Unscrew the spindle clockwise

and take away the service tool.

– Take out the two M5x72 screws.

44 MS 240, MS 260, MS 260 C

Page 46

: Use a 4 mm dia. drift to drive

home the dowel pin at the chain tensioner side until the pin is flush with the hole at the other side.4 m

165RA117 TG165RA097 TG

: Fit the washer (1) and ring (2).

– Check and install the piston,

b 8.7.2

– Check and install the cylinder,

b 8.5

– Reassemble all other parts in the

reverse sequence.

8.6.2 Bearings / Crankcase

Each half of the crankcase can be replaced separately if it is damaged.

New crankcase halves are supplied with the main parts preassembled – see the parts list. Parts not supplied with the new crankcase must be transferred from

165RA075 TG

the original crankcase – check the parts and replace if necessary.

If a new crankcase is installed, the machine's serial number must be stamped on it with 2.5 mm figure stamps.

If the original crankcase is used again, replace the oil seals and ball bearings, remove any gasket residue and clean the sealing surfaces thoroughly. The sealing faces must be clean to guarantee a perfect seal.

: Insert the screws (arrows) and

tighten them down firmly in an alternate pattern.

– Tightening torques, b 3.5

Inspect both halves of the crankcase for cracks and all sealing faces for signs of damage.

– See also Troubleshooting,

b 4.7

– Remove the crankshaft, b 8.6.1

– Wear protective gloves to reduce

the risk of burn injury.

45MS 240, MS 260, MS 260 C

Page 47

Ignition side of crankcase

: Use a suitable punch to carefully

drive out the oil seal.

: Check and clean the crankcase

or replace if necessary.

If this half of the crankcase is in order, install a new ball bearing.

– Heat the area of the bearing seat

165RA137 TG

to about 150 °C (300 °F).

– Position the ball bearing so that

its open side (balls visible) face the outside of the crankcase.

: Push the ball bearing home as far

as stop.

This operation must be carried out quickly because the bearing absorbs heat and begins to expand.

Check that the bearing is properly seated and, if necessary, use the

165RA138 TG

press arbor 1120 893 7200 to press it fully into the bearing seat.

Clutch side of crankcase

165RA140 TG

: Check and clean the crankcase

or replace if necessary.

If this half of the crankcase is in order, install a new ball bearing.

– Heat the area of the bearing seat

to about 150 °C (300 °F).

The bearing (1) drops out as soon as this temperature is reached.

165RA142 TG

165RA143 TG

As the clutch side of the crankcase does not have a fixed bearing seat, the oil pump must be installed before the ball bearing – the oil pump then serves as the stop.

– Install the oil pump,

165RA141 TG

: Use a suitable punch to carefully

165RA139 TG

drive out the oil seal.

adjustable, b 13.5, non-adjustable, b 13.4

– Heat the area of the bearing seat

to about 150 °C (300 °F).

The bearing (1) drops out as soon as this temperature is reached.

46 MS 240, MS 260, MS 260 C

Page 48

– Heat the area of the bearing seat

to about 150 °C (300 °F).

– Position the ball bearing so that

the centering ring (arrow) points toward the oil pump.

: Push the ball bearing home as far

as stop (oil pump).

This operation must be carried out quickly because the bearing absorbs heat and begins to expand.

8.7 Piston

8.7.1 Removal

Before removing the cylinder, decide whether or not the crankshaft has to be removed as well, b 8.6

– Remove the cylinder, b 8.5

165RA480 TG

Note when removing the snap rings that the installing tool 5910 890 2210 can only be applied to the igniton side – the snap ring at the clutch side must be installed first.

: Use the assembly drift (2)

1110 893 4700 to push the piston pin (1) out of the piston.

If the piston pin (1) is stuck, release it by tapping the end of the drift (2) lightly with a hammer. Hold the piston steady during this process to ensure that no jolts are transmitted to the connecting rod.

165RA147 TG

Check that the ball bearing is properly seated and, if necessary, use press arbor 1118 893 7200 to press it home against the oil pump – too much pressure may damage the oil pump.

– Remove the adjustable oil pump,

b 13.5

– Remove the non-adjustable oil

pump, b 13.4

– Install the crankshaft, b 8.6.1

– Install the oil seals,

b 8.3

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

: Pry both hookless snap rings out

of their grooves by applying a suitable tool to the recess (arrow).

: Place the assembly drift (1)

1110 893 4700 in position.

165RA145 TG

: Remove the piston (1) from the

connecting rod.

– Inspect the piston rings and

replace if necessary, b 8.8

165RA146 TG

165RA148 TG

47MS 240, MS 260, MS 260 C

Page 49

8.7.2 Installing

: Pull out the needle cage (1),

check it and replace if necessary.

– Lubricate the needle cage (1)

with oil and push it into the connecting rod.

– Install the snap ring in the piston

boss at the clutch side – the assembly drift 1110 893 4700 can be pushed through the installed snap ring.

– Lubricate the piston pin with oil.

165RA149 TG

: Fit the piston pin (1) on the

assembly drift (2) and slide it into the piston.

The piston has a snap ring at both sides. The snap ring at the clutch side must be installed first.

165RA150 TG

: Remove the sleeve (1) from the

installing tool 5910 890 2210.

165RA151 TG

165RA154 TG

: Push the large slotted diameter of

the sleeve over the magnet and snap ring.

The inner pin must point towards the flat face of the tool's shank.

165RA155 TG

: Press the installing tool

165RA152 TG

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

Use a suitable base.

– Line up the piston so that the

arrow on the piston crown points toward the exhaust port/muffler.

– Place the piston on the

connecting rod.

: Push the assembly drift (1)

1110 893 4700, small diameter

165RA153 TG

first, through the piston and small end (needle cage) and line up the piston.

: 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).

48 MS 240, MS 260, MS 260 C

Page 50

8.8 Piston Rings

– Remove the piston, b 8.7.1

: Remove the sleeve and slip it

onto the other end of the shank – the inner pin must point towards the flat face.

: Apply the installing tool

5910 890 2210 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.

165RA156 TG

Fit the snap ring (1) so that its gap (arrow) points either up or down.

– Inspect the piston rings and

165RA157 TG

replace if necessary, b 8.8

– Install the cylinder, b 8.5

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

– Remove the piston rings from the

piston.

165RA158 TG

165RA160 TG165RA161 TG

: Use a piece of old piston ring to

scrape the grooves clean.

165RA159 TG

: Install the new piston rings in the

grooves so that the radii face upward (arrows).

49MS 240, MS 260, MS 260 C

Page 51

8.9 Decompression Valve

165RA162 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 8.7.2

– Reassemble all other parts in the

reverse sequence.

165RA163 TG

– Remove the shroud, b 8.4

: Remove the cover (1).

: Unscrew the decompression

valve (2).

165RA164 TG

: Check the sealing cone (arrow)

on the decompression valve for damage.

If the sealing cone does not close completely or shows signs of damage, install a new decompression valve.

– Fit the decompression valve and

screw it home by hand.

– Tighten down the decompression

valve firmly.

– Tightening torques, b 3.5

– Reassemble all other parts in the

reverse sequence.

50 MS 240, MS 260, MS 260 C

Page 52

9. 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 4.5

– Remove the fan housing,

b 10.2

9.2 Ignition Module

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

– the high voltage output (1) for the

ignition lead

– the connector tag (2) for the short

circuit wire

165RA165 TG

9.2.1 Removing and Installing

– Remove the fan housing,

b 10.2

165RA166 TG

: Unscrew the slotted nut (arrow).

– Remove the shroud (1).

165RA168 TG

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

9.1 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.

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 9.2.1.

165RA167 TG

: Turn twist lock (1)

counterclockwise.

– Remove the carburetor box

cover (2).

51MS 240, MS 260, MS 260 C

Page 53

: Pull boot (1) off the spark plug.

: Take out the screw (arrow).

– Remove the retaining plate (1).

165RA009 TG

– Disengage the connector.

: Disconnect the short circuit

wire (1) – do not pull it out of the retainer.

: Take out the screws (arrows).

– Remove the ground wire (2).

165RA169 TG

165RA171 TG

: Use a suitable punch to drive out

the retainer (1).

– Check the retainer and replace if

necessary

– Check the spark plug boot and

ignition lead, and replace if necessary, b 9.4

– Reassemble in the reverse

sequence.

– Troubleshooting, b 4.5

Versions with handle heating

165RA172 TG

165RA174 TG

: Pull the ignition lead (1) out of its

guide (arrow).

: Remove the ignition module (1).

165RA169 TG

: Pull the grommet (1) off the

ignition module.

: Unscrew the ignition module from

the ignition lead (2).

: Before installing the ignition

module, check that the generator wire (arrows) is properly positioned, b 15.7

165RA173 TG

165RA175 TG

52 MS 240, MS 260, MS 260 C

Page 54

: Rotate the flywheel until the

magnet poles (arrows) are next to the ignition module.

– Press the ignition module (1)

against the setting gauge.

– Tighten down the screws firmly.

– Tightening torques, b 3.5

165RA176 TG

165RA180 TG

: Fit the ignition module (1) and

insert the screw (arrow) – do not tighten down yet.

: Fit the ground wire (2) and insert

the screw (arrow) – do not tighten down yet.

– Slide the setting gauge (1)

1111 890 6400 between the arms of the ignition module and the flywheel magnet.

– Remove the setting gauge.

– Check operation

– rotate the flywheel and make sure it does not touch the ignition module (1).

165RA178 TG

: Position the ignition lead with

insulating tube (1) in the guides (arrows).

: Fit the retaining plate (2), insert

the screw and tighten it down firmly.

: Connect the short circuit wire (1)

and push it into the retainer (arrow).

165RA181 TG

: Push the wiring harness (1) into

the guides (arrows).

165RA179 TG

Versions with handle heating

The setting gauge is not shown in the illustration.

: Push the ignition module (1) back

and hold it thee – the flywheel must turn freely.

– Position of insulating tube:

a = about 2 - 5 mm – the ignition lead may otherwise be damaged by chafing.

165RA496 TG

165RA046 TG

: Push the pin and socket

connector (1) into the guide (arrow).

– Fit the wiring harness with short

circuit wire in position, b 15.8 and b 9.6.2

53MS 240, MS 260, MS 260 C

Page 55

9.3 Testing the Ignition Module

The engine may start and accelerate during the test.

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.

Using the ZAT 4 ignition tester 5910 850 4503

– Before starting the test, install a

new spark plug in the cylinder and tighten it down firmly.

– Tightening torques, b 3.5

: Connect spark plug boot to the

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

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 9.7

3 4

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.

– Tightening torques, b 3.5

: Connect spark plug boot to the

terminal (2).

: Attach the ground terminal (1) to

the spark plug.

3 4

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

High voltage – risk of electric shock.

165RA184 TG

– 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 in the window (3), 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 9.7

165RA185 TG

High voltage – risk of electric shock.

– Crank the engine quickly with the

rewind starter and check spark in the tester’s window (2).

54 MS 240, MS 260, MS 260 C

: Use adjusting knob (4) to set the

spark gap to about 2 mm, see spark window (3).

Page 56

9.4 Spark Plug Boot / Ignition Lead

– Remove the ignition module,

b 9.2.1

: Pull the grommet (1) off the high

voltge output (arrow).

– Cut a new ignition lead to the

specified length, see parts list.

– Use a pointed tool to pierce the

center of the new ignition lead’s insulation, about 15 mm from the end of the lead.

165RA481 TG

165RA190 TG165RA191 TG

: Make sure the leg spring (arrow)

locates properly inside the spark plug boot.

165RA188 TG165RA189 TG

– Unscrew the ignition lead (2) from

the contact pin and pull it out of the high voltage output.

– Pull the grommet (1) off the

ignition lead.

: Use suitable pliers to pull the leg

spring out of the spark plug boot.

– Unhook the leg spring from the

ignition lead.

: Pinch the hook of the leg spring

into the center of the lead (arrow).

– Coat the inside of the spark plug

boot with STIHL press fluid, b 17

165RA187 TG

: Hold the ignition lead and leg

spring together and push them into the spark plug boot.

: Use a pointed tool to pierce the

center of the other end of the ignition lead which screws into the module.

– Fit the grommet.

Do not use either graphite grease or silicone insulating paste.

– Install the ignition module and set

the air gap between the module and flywheel, b 9.2.1

– Reassemble all other parts in the

reverse sequence.

– Pull the boot off the ignition lead.

55MS 240, MS 260, MS 260 C

Page 57

9.5 Flywheel

– Remove the carburetor box

cover.

– Remove the shroud, b 8.4

– Block the piston with the locking

strip (1) 0000 893 5903, b 6

: Unscrew the flywheel nut (arrow).

: Screw the puller (1) 1110 890

165RA011 TG

4500 clockwise into the flywheel as far as stop.

: Use 24 mm open end wrench (3)

to hold the puller steady and screw home the thrust bolt (2) until the flywheel is released from the crankshaft.

– Remove the puller (1) 1110 890

4500 from the flywheel.

165RA192 TG

The flywheel and magnet poles (arrows) must not be damaged or have turned blue. Replace flywheel if necessary.

On versions with handle heating, also check the magnet ring for signs of damage, b 15.7.

165RA193 TG

– Check the key (1) and replace if

necessary

– Make sure the key (arrow) is

properly seated.

Degrease the crankshaft stub and bore in flywheel with a standard solvent-based degreasant containing no chlorinated or halogenated hydrocarbons.

165RA194 TG

: Make sure the key engages the

slot (arrow) in the flywheel.

– Set the air gap between the

ignition module and flywheel, b 9.2.1

– Reassemble all other parts in the

reverse sequence.

165RA195 TG

165RA196 TG

The flywheel and crankshaft stub must be free from grease before

– Tightening torques, b 3.5

assembly.

56 MS 240, MS 260, MS 260 C

Page 58

9.6 Short Circuit Wire

9.6.1 Testing

9.6.2 Removing and Installing

– Remove the shroud, b 8.4

– Remove the fan housing,

b 10.2

– Remove the carburetor, b 14.2

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

– Remove the fan housing, b 10.2

: Disconnect the short circuit wire

(1).

– Connect the ohmmeter to ground

(arrow) and the short circuit wire (1).

– Set the switch shaft to "

The resistance measured must be about 0 Ω. If it is much higher, the reason is a break and the wire has to be replaced, b 9.6.2.

– Set the switch shaft to "F".

The resistance measured must be infinitely high. If not, fit a new short circuit wire, b 9.6.2.

0".

The ground and short circuit wires are combined in a wiring harness.

165RA197 TG

: Pull the short circuit wire (1) out

of the retainer (arrow), disengage and remove the connector (2).

: Take out the screw and remove

the ground wire (3).

Versions with handle heating

: Pry out the grommet (arrow).

The wire for handle heating is also included in the wiring harness and

grommet, and has to be removed as well b 15.8.

165RA198 TG

– Pull the short circuit wire out of

the guide (arrow).

: Remove the connectors of the

short circuit wire (1) and ground wire (2).

165RA200 TG

165RA482 TG

If no fault can be found, check the ignition system with the aid of the troubleshooting chart, b 9.7.

– Reassemble in the reverse

sequence.

165RA199 TG

: Pull the wiring harness (1) out of

the guides (arrows).

: Pull the pin and socket connector

(2) out of the guide and separate it.

57MS 240, MS 260, MS 260 C

Page 59

A faulty ground wire may impair or prevent operation of the short circuit wire, and the heating on versions with handle heating.

Perform the contact and continuity test on the ground wire too.

Versions with handle heating

165RA202 TG

165RA207 TG

– Pull the wiring harness out of the

opening (arrow).

– Remove the switch shaft,

b 12.1.1

: Push the retainer (arrow)

carefully in the direction of the guide slot and pull out the contact spring (1).

Check the additional wire (1) in the wiring harness and replace the wiring harness if necessary, b 15.8.

165RA203 TG

If any of the wires are damage, always replace the complete wiring harness.

Make sure the retaining lug (arrow) locks the contact spring in position.

165RA205 TG

165RA208 TG

: Thread the end of the wiring

harness with the sockets through the opening (arrow).

Versions with handle heating

: Push the contact spring (1) into

its guide (arrow) as far as stop.

165RA204 TG

: Inspect the wiring harness (1),

contact spring (2), grommet (3) and all connectors, and replace wiring harness if necessary.

58 MS 240, MS 260, MS 260 C

165RA483 TG

– Connect the pin and socket

connector, push the insulating tube over the connector so that it is completely covered, b 15.8

165RA484 TG

Page 60

Start installation and connector of the short circuit wire at the ignition module.

: Connect the short circuit wire (1)

and push it into the retainer (arrow).

: Fit the ground wire (1), insert the

screw and tighten it down firmly.

When tightening, make sure the terminal does not butt against the housing.

165RA210 TG

: Fit the grommet (arrow) in the

opening and make sure it is properly seated.

– Use STIHL press fluid to simplify

assembly, b 17

165RA211 TG

: Push the short circuit wire with

insulating tube (1) into the guides (arrows).

: Push the pin and socket

connector (2) into its guide.

165RA212 TG

: Push connector (1) of ground

wire (greem/yellow) into the contact spring as far as stop.

: Push connectot (2) of short circuit

wire into the switch shaft as far as stop.

– Install the switch shaft, b 12.1.1

165RA499 TG

: Push the wire into the guide

(arrow).

165RA214 TG

165RA215 TG

– Check air gap on ignition module

and reset if necessary, b 9.5

165RA485 TG

: Position the ground wire (1)

behind the stop buffer (arrow).

59MS 240, MS 260, MS 260 C

Page 61

165RA497 TG

9.6.3 Ground Wire

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

The ground wire is combined with the short circuit wire in a wiring harness. If damaged, the complete wiring harness must be replaced

165RA209 TG

Versions with handle heating

: Push the pin and socket

connector into the guides (arrows).

: Position the wire (1) behind the

pin and socket connector.

– Install the carburetor, b 14.2

– Reassemble all other parts in the

reverse sequence.

– Check for contact and continuity

and replace wiring harness if necessary, b 9.6.2 Versions with handle heating, b 15.8

– Tightening torques, b 3.5

– Check operation.

60 MS 240, MS 260, MS 260 C

Page 62

9.7 Ignition System Troubleshooting

Engine does not run

Stop switch:

– in position "F"?

Check the spark plug:

– Smeared with oil, black?

– Sooted?

– Electrode gap correct?

– Contacts shorted?

– Clean, readjust or replace the plug,

b 9.3

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 9.4

Test ignition system:

with ZAT 3 or ZAT 4

(use ZAT 3 as main spark gap

see TI 32.94),

b 9.3

61MS 240, MS 260, MS 260 C

Page 63

Powerful spark?

Air gap:

– Check ignition module/flywheel,

– reset if necessary, b 9.2.1

Check the flywheel:

– Have pole shoes turned blue?

– Install new flywheel if necessary,

b 9.5

Check short circuit wire:

– Wire damaged?

– Connectors firmly seated?

– Check the short circuit wire for break and

replace if necessary, b 9.6.1

yes

Check the ignition lead:

– Severe chafing?

– Spark plug boot: Holes/cracks?

– Resistance: spark plug boot to ground: spec.

1.5 – 12 kΩ

– Check resistance of ignition lead

: spec. < 10 Ω,

If necessary, install new spark plug boot and/or

ignition lead with module,

b 9.4

62 MS 240, MS 260, MS 260 C

Page 64

Check operation

of switch shaft:

– Short circuit wire chafed?

– Function between contact spring and switch

shaft contact:

– Position "F" = no connection

– Position "

– Install new short circuit wire if necessary,

0" = connection

b 9.6.2

yes

Powerful spark?

Install new

ignition module,

b 9.2.1

Engine runs

yes

Machine runs trouble-free,

no further action necessary

– Look for fault in fuel system or

carburetor

– Check engine for leaks

– Check position of flywheel on

crankshaft,

b 8.2, b 9.5

63MS 240, MS 260, MS 260 C

Page 65

10. Rewind Starter

10.1 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 solventbased degreasant (containing no chlorinated or halogenated hydrocarbons) to the rewind spring.

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

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

10.2 Removing and Installing

: Take out the screws (arrows).

– Lift the hand guard (1) a little and

remove the fan housing (2).

10.3 Pawl

165RA217 TG

– Remove the fan housing,

b 10.2

: Carefully ease the spring clip (1)

off the starter post.

165RA219 TG

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.

– Lift the hand guard a little and fit

the fan housing in position.

: Insert the screws (arrows)

– screw (1) with sleeve secures the hand guard as well.

– Tighten down the screws firmly.

– Tightening torques, b 3.5

165RA218 TG

165RA220 TG

: Remove the pawl (1).

165RA221 TG

– Fit the new pawl in the bore

(arrow) and lubricate its peg (1), b 17

64 MS 240, MS 260, MS 260 C

Page 66

: Position the spring clip (1) so that

its loop engages the peg on the pawl and its curved end (arrow) is in the starter post’s groove.

: Push the straight part of the

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

– Reassemble all other parts in the

reverse sequence.

– Pull out the rope with the starter

grip and slowly release the rope rotor.

– Remove the starter rope or

remaining rope from the rotor, b 10.5

The system will not be under tension if either the starter rope or

165RA222 TG

rewind spring is broken.

– Remove the spring clip and pawl,

b 10.3

165RA225 TG

: Fit the rope rotor on the starter

post so that the inner spring loop (arrow) engages the recess (1).

The opening (1) in the hub of the rope rotor is the anchor point for the spring.

– Fit the washer.

– Install the pawl and spring clip,

b 10.3

10.4 Rope Rotor

Relieving tension of rewind spring

– Remove the fan housing,

b 10.2

: Pull out the starter rope (1)

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

– Take three full turns of the rope

off the rope rotor.

– Remove the washer (1).

Rewind spring must be relaxed.

: Carefully remove the rope rotor

(2).

– Check the rope rotor and replace

if necessary.

– Coat bore in rope rotor with

STIHL special lubricant,

165RA223 TG

b 17

– Install the starter rope, b 10.5

165RA224 TG

– Tension the rewind spring,

b 10.6

– Lubricate peg on pawl with

grease, b 17

65MS 240, MS 260, MS 260 C

Page 67

10.5 Starter Rope / Grip

Machines with ElastoStart Grip

– Remove the fan housing and the

segment, b 10.2

– Relieve tension of rewind spring,

b 10.4

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.

– Remove the rope rotor, b 10.4

: Use a suitable tool to pry the cap

(1) out of the starter grip.

: Thread the new starter rope (1)

165RA230 TG

through the sleeve.

– Tie a simple overhand knot in the

end of the rope.

– Fit the washers and spring.

– Pull the starter rope with sleeve,

spring and washers into the starter grip (1).

Make sure the washers and spring remain on the sleeve while the rope its being pulled into the grip.

165RA231 TG

165RA233 TG

: Push the end of the starter rope

(1) out a little and undo the knot.

– Pull the starter rope out of the

rope rotor and fan housing.

: Pull the sleeve, washers, spring

165RA226 TG

and remaining rope (arrow) out of the grip.

– Pull any remaining rope out of the

sleeve. Inspect the individual parts and replace if necessary.

Do not shorten the starter rope.

165RA234 TG

: Position cap so that its lug (1)

engages the slot (arrow) in the starter grip.

– Press the cap into the starter grip.

66 MS 240, MS 260, MS 260 C

Page 68

Machines with Standard Starter Grip

– Pull the rope out of the starter

grip.

: Thread the starter rope (1)

through the guide bushing

165RA227 TG

(arrow).

– Install the rope rotor and tension

the rewind spring, b 10.4

– Install the fan housing,

b 10.2

– Tightening torques, b 3.5

10.6 Tensioning the Rewind

165RA235 TG

Spring

: Tie one of the special knots

shown in the end of the rope.

: Thread the rope through the top

of the starter grip.

: Thread the starter rope (1)

through the side of the rope rotor.

– Secure the rope (1) with a simple

165RA228 TG

overhand knot.

165RA238 TG

– Remove the fan housing,

b 10.2

165RA236 TG

: Pull out a short length of starter

rope (1).

: Use the starter rope (1) to rotate

the rope rotor (2) six turns clockwise,

Rotating the rope and rope rotor causes the rope to become twisted. The rewind spring is now tensioned.

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

: Pull the rope with knot into the

starter grip until it is properly seated in the grip (small arrow).

165RA237 TG

533RA190 TG

: Pull rope back until knot (1)

locates in recess (arrow) in rope rotor.

67MS 240, MS 260, MS 260 C

Page 69

Spring

– Troubleshooting, b 4.4

The replacement spring, in a spring housing, comes ready for installation.

Wear a face shield and work gloves.

10.7 Replacing the Rewind

165RA237 TG

165RA241 TG

– 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.

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:

165RA240 TG

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

– Install the fan housing,

b 10.2

– Tightening torques, b 3.5

– Remove the fan housing,

b 10.2

– Relieve tension of rewind spring if

necessary and remove the rope rotor, b 10.4

– Remove any remaining pieces of

old spring.

– Lubricate the spring with a few

drops of STIHL special lubricant before installing, b 17

165RA243 TG

: Line up the replacement spring

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

: Push the rewind spring with

spring housing into its seat (arrow) in the fan housing.

The rewind spring may pop out and unwind.

68 MS 240, MS 260, MS 260 C

Page 70

Check that the rewind spring (1) is properly seated and the anchor loop engages the lug (arrow).

If the rewind spring has popped out, refit it in the fan housing as follows:

– Arrange the spring (1) in its

original position.

The position of the anchor loop cannot be changed after the rewind spring is fitted in the spring housing.

: Place the anchor loop in the

spring housing (arrow).

Distance from the end of the anchor loop to the edge of the spring housing a = 20 mm.

165RA244 TG

: Fit the rewind spring (1)

counterclockwise in the housing, starting from outside and working inwards.

– Hold the spring windings so that

they cannot pop out.

165RA245 TG

– Secure the spring so that it

cannot pop out.

: Use suitable pliers to position the

inner spring loop (1) so that it is against the starter post.

– Install the rope rotor, b 10.4

– Reassemble all other parts in the

reverse sequence.

165RA077 TG

165RA246 TG

69MS 240, MS 260, MS 260 C

Page 71

11. Servicing the AV System

Vibration-damping rubber buffers are used for the connection between the handlebar, tank housing and engine housing.

Damaged rubber buffers (annular buffers) must always be replaced.

11.1 Annular Buffer on Chain Catcher

Always replace a damaged annular buffer.

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the side plate, b 7.6

– Use STIHL press fluid to simplify

assembly, b 17

– Hold annular buffer with its small

diameter (1) facing the housing.

: Push the annular buffer (1) into

the bore until its groove (arrow) engages the housing rib (2).

– Insert screw and tighten it down

firmly.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

11.2 Annular Buffer at Clutch Side

– Remove the sprocket cover and

165RA250 TG

cutting attachment, b 5

165RA253 TG

: Insert screw (arrow) part way and

pull out the plug (1).

: Take out the screw (arrow).

165RA248 TG

: Position the plug (1) so that its

recesses match those on the housing (see arrows).

– Push the plug into the annular

buffer as far as stop.

– Use STIHL press fluid to simplify

165RA249 TG

assembly, b 17

: Pry out the plug(1).

165RA251 TG

165RA254 TG

: Take out the screw (arrow).

– Pry out the annular buffer (1).

70 MS 240, MS 260, MS 260 C

Page 72

: Pry out the annular buffer (1).

– Check the annular buffer (1) and

replace if necessary

1 2

– Hold the annular buffer (1)

with its small diameter facing the crankcase.

– Use STIHL press fluid to simplify

assembly,

b 17

: Push the annular buffer (1) into

the bore until its groove (arrow) engages the housing rib (2).

165RA486 TG

– Position the tank housing on the

annular buffer – the holes must line up.

: Insert screw (arrow) and tighten it

down firmly.

– Push the plug into the annular

buffer as far as stop.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA256 TG

11.3 Annular Buffer at Ignition Side

– Remove the shroud, b 8.4

165RA254 TG165RA257 TG

: Take out the screws (arrows) and

remove the retaining plate (2).

– Remove the annular buffer (1).

– Check the annular buffer (1) and

replace if necessary

– Hold the annular buffer (1)

with its tapered side facing the crankcase.

– Fit the annular buffer (1) in

position.

– Fit the retaining plate (2) in

position.

165RA258 TG

165RA242 TG

– Push the wiring harness (1) to

one side.

: Take out the screw (arrow) and

remove the washer (2).

– Check that the ignition lead is in

its guide and not pinched.

: Insert screws (arrows) and

tighten them down firmly.

71MS 240, MS 260, MS 260 C

Page 73

11.5 Handlebar

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the shroud, b 8.4

– Position the tank housing on the

annular buffer – the holes must line up.

– Fit the washer (1).

: Insert screw (arrow) and tighten it

down firmly.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

11.4 Stop Buffer

– Remove the carburetor, b 14.2

– Take out the annular buffer/tank

housing mounting screws. Annular buffer at ignition side, b 11.3. Annular buffer at clutch side, b 11.2

165RA259 TG

Lower the tank housing a little – check that the impulse is pushed fully onto the connector on the crankcase.

: Ease the stop buffer (1) out of the

bore.

– Check the stop buffer (1) and

replace if necessary

– Position the stop buffer (1) so that

its tapered side (arrow) faces away from the tank housing.

165RA498 TG

165RA262 TG

: Remove the screws (arrows)

from the underside of the machine.

165RA261 TG

165RA263 TG

: Take out the screws (arrows).

– Push the manifold out of the tank

housing, b 14.6.1

: Push the stop buffer (1) into the

bore and make sure it is properly seated.

– Pull off the impulse hose,

b 14.6.2

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

72 MS 240, MS 260, MS 260 C

Page 74

– Take out the annular buffer/tank

housing mounting screws. Annular buffer at ignition side, b 11.3.

Annular buffer at clutch side, b 11.2

– Remove the interlock lever,

b 12.2

: Push the handlebar (1) out of its

seat on the underside of the machine.

– Remove the handlebar (1), check

it and replace if necessary.

: Position the handlebar (1) in its

seat (arrow) and insert the screws.

165RA264 TG

: Position the handlebar (1) in its

seat on the side of the machine (arrow) and insert the screws.

– Check that the handlebar is

properly seated and then tighten down all four screws firmly.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

11.6 Handlebar with Handle Heating

165RA487 TG

The handlebar in these versions is equipped with a heating system – the electrical wires have to be disconnected.

– Troubleshooting, b 15.3.1

165RA266 TG

– Remove the switch shaft,

b 12.1.1

– Push the manifold out of the tank

housing, b 14.6.1

– Pull off the impulse hose,

b 14.6.2

– Remove the heater switch,

b 15.4

– Remove the ground wire from the

housing cover, b 15.4.1

– Lower the tank housing for easier

access.

Apart from the electrical connections, the removing and installing procedures are the same as for the handlebar without heating, b 11. 5.

– Remove the carburetor, b 14.2

165RA267 TG

During all the following procedures:

: To reduce the risk of a short

circuit, make sure the insulating tubes completely cover the connections.

73MS 240, MS 260, MS 260 C

Page 75

Removing the Handlebar

– Push the insulating tube (1) in the

directon of the heating element.

: Separate the pin and socket

connector (arrow).

: Take the wire (1) with insulating

tube (2) out of the guide (arrow).

– Pull the handle heating wire (1)

out of the insulating tube (2).

: Pull the wiring harness out of the

165RA268 TG

hole (arrow) in the housing in the direction of the cylinder.

: Pull the wiring harness out of the

hole (arrow).

165RA269 TG

– Remove the handlebar, check it

and replace if necessary

– Test the handle heating system,

b 11.6

165RA270 TG

: Place the handlebar in position

and continue pulling the wiring harness (1) through the hole until it is snugly seated in the recess (arrow).

165RA271 TG

: Thread the wiring harness (1)

through the hole (arrow) until it locates snugly against the tank housing.

165RA273 TG

165RA274 TG

Installing the Handlebar

: Push the wire with connector

sleeve (1) through the hole (arrow) and position it in the

165RA272 TG

guide.

: Thread the wiring harness

through the hole (arrow).

74 MS 240, MS 260, MS 260 C

– Install the heater switch, b 15.4

165RA275 TG

Page 76

: Push the wire (1) through the

insulating tube (2).

: Push the pin and socket together

until they lock.

– Push the insulating tube (1) over

the connectors.

165RA276 TG

: Push the wires with the insulating

tube (1) into the guide.

The wires and insulating tube (1) must not project – risk of chafing on switch shaft or throttle rod.

165RA277 TG

– Position the wires without loops.

: Arrange the connectors and

wires (arrows) on the heating element so that they are not pinched.

165RA278 TG

– The ground wire ring terminal (2)

must be in position on the heater switch.

: Position the handlebar (1) so that

the heater switch engages the opening (arrow).

– Secure the handlebar, b 11.5

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA279 TG

165RA280 TG

: Push the wire (1) into the guide

(arrow) – position the wire snugly against the housing.

: Position the wire (2) behind the

fuel hose.

165RA330 TG

75MS 240, MS 260, MS 260 C

Page 77

12. Control Levers

12.1 Switch Shaft

The following positions can be selected with the switch shaft:

– Position

0 = engine off

– ignition is switched off

– Position F = normal run position

– engine runs or may start in this position

To move the switch shaft from F to k or l depress the interlock lever and throttle trigger at the same time.

12.1.1 Removing and Installing

165RA281 TG

– Remove the air filter, b 14.1

– Remove the handle molding,

b 12.2

: Disconnect the throttle rod (1)

from the trigger (2).

: Pry the switch shaft (1) out of its

165RA282 TG

mount (arrow).

– Lift the switch shaft (1) a little and

pull it out of the mount (2).

– Check the switch shaft (1) and

replace if necessary

165RA284 TG

– Position k = warm start

– warm engine is started in this position

The switch shaft returns to the run position when the throttle trigger is operated.

– Position k = cold start

– cold engine is started in this position

: Pull terminal sleeve (arrow) of

short circuit wire (1) out of the switch shaft.

165RA283 TG

– Line up the switch shaft

– the arm (arrow) must point in the direction of the throttle trigger.

: Push the switch shaft into the

mount (1).

165RA285 TG

76 MS 240, MS 260, MS 260 C

Page 78

12.2 Throttle Trigger/Interlock Lever

– Line up the switch shaft

– the lever (1) must locate in the guide (arrow).

: Press the switch shaft into the

mount (2) until it snaps into position.

: Push terminal sleeve (1) of short

circuit wire into the bore (arrow) as far as stop.

165RA286 TG

– The contact spring (1) must butt

against the switch shaft's (2) guide.

: Move switch shaft to "

0" –

contact between the short circuit wire and contact spring (arrow) must be made.

165RA287 TG

: Attach the throttle rod (1) to the

trigger (2).

165RA288 TG

– Remove the air filter, b 14.1

: Take out the screw (arrow).

165RA335 TG

: Remove the handle molding (1).

The interlock lever (arrow) may pop out.

165RA289 TG

165RA290 TG

– Fit the handle molding, b 12.2

– Check correct position of short

circuit wire, b 9.6.2

– Check operation.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

: Disconnect the throttle rod (1)

from the trigger (2).

165RA282 TG

77MS 240, MS 260, MS 260 C

Page 79

: Ease the interlock lever (1) out of

its mounts (arrows).

– Disconnect the torsion spring and

remove the interlock lever.

2 1

: Use a drift (2) to drive out the pin

(1).

165RA291 TG

– Check the interlock lever (1),

trottle trigger (2) and torsion spring (1) and replace if necessary

Versions with handle heating

165RA292 TG

Make sure the wires are properly positioned in the guide (arrows).

165RA294 TG

: Fit the throttle trigger (1) in the

rear handle so that its lug is behind the arm on the switch shaft (arrow).

: Use a drift (2) to line up the

165RA295 TG

throttle trigger (1).

: Drive home the pin (3) until it is

centered (recessed by same amount at both sides).

165RA297 TG

165RA298 TG

165RA293 TG

– Set the switch shaft to "

0".

: Attach the torsion spring (1) to

the throttle trigger (2)

: Remove the throttle trigger (1)

– note installed position (arrow).

with torsion spring (2).

78 MS 240, MS 260, MS 260 C

165RA296 TG

Page 80

1 2

When installing the interlock lever, make sure its stop (1) engages the recess in the throttle trigger.

: Attach the torsion spring (2) to

the interlock lever (arrow).

124

– Squeeze the throttle trigger (1)

until the lever (2) is vertical and hold it there.

165RA299 TG

: Attach the throttle rod (1) to the

trigger (2).

Versions with handle heating

– Arrange the connectors and

165RA300 TG

wires (arrows) on the heating element so that they are not pinched.

165RA335 TG

: Engage tab of handle molding (1)

in the opening (arrow).

– Position the handle molding (1)

over the switch shaft and interlock lever, making sure the throttle rod remains attached to the trigger – the handle molding holds the throttle rod in place.

– Hold the handle molding in

position.

– Insert screw from below and

tighten it down firmly.

165RA301 TG

– Check operation.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA302 TG

: Push the interlock lever (3) into

its pivot mounts (arrows) until it snaps into position – check that torsion spring (4) is in position.

The interlock lever may pop out.

79MS 240, MS 260, MS 260 C

Page 81

13. Chain Lubrication

13.1 Pickup Body

Impurities gradually clog the fine pores of the filter with minute particles of dirt. This prevents the oil pump from supplying sufficient oil. In the event of problems with the oil supply system, first check the oil tank and the pickup body. Clean the oil tank if necessary, b 1

– Troubleshooting, b 4.3

– Open the oil tank cap and drain

the oil tank.

– Collect chain oil in a clean

container, b 1

13.2 Oil Suction Hose

– Remove the sprocket cover and

cutting attachment, b 5

– Remove the clutch, b 6

– Remove the brake band, b 7.2

– Remove the adjustable oil pump,

b 13.5

– Remove the non-adjustable oil

pump, b 13.4

– Open the oil tank cap and drain

the oil tank.

– Collect chain oil in a clean

container, b 1

165RA305 TG

: Push the oil suction hose (1),

pickup body first, through the housing bore (arrow).

: Use hook (2) 5910 893 8800 to

remove the pickup body (1) from the oil tank.

Do not overstretch the suction hose.

165RA303 TG

: Remove the oil suction hose (1).

– Check the oil suction hose and

pickup body and replace if necessary. Install the pickup body, b 13.1

: Line up the oil suction hose (1)

– the tab (arrow) must be in the guide.

– Push home the oil suction hose

(1) until its groove is properly

165RA304 TG

seated in the crankcase.

– Check position of pickup body. If

necessary, use hook 5910 893 8800 to position it properly.

– Install the oil pump,

adjustable, b 13.5, non-adjustable, b 13.4

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA306 TG

80 MS 240, MS 260, MS 260 C

Page 82

13.3 Oil Delivery Hose

– Remove the worm, b 13.5

13.4 Non-Adjustable Oil Pump

– Take out the screws.

: Remove the oil pump (1) and

disconnect the oil delivery hose (arrow).

– Check the oil pump (1) and

replace if necessary

: Fit the new oil delivery hose (1)

through the bore (arrow) from outside.

165RA307 TG

– Use a suitable tool to carefully

push the oil delivery hose into the bore until it is recessed a = 2 mm behind the edge of the bore (arrow).

– Reassemble all other parts in the

reverse sequence.

165RA308 TG

165RA309 TG

165RA311 TG

The procedures for removing and installing the non-adjustable oil pump are the same as those for the adjustable oil pump, b 13.5

Non-adjustable oil pumps cannot be repaired and must be replaced in the event of a fault.

165RA310 TG

165RA312 TG

This version has no driver on the worm.

: Use a suitable tool to push the

sleeve and oil delivery hose through the bore (arrow).

Take care not to damage the bore (arrow).

The oil delivery hose with sleeve is damaged during the removal process and has to be replaced – the new hose comes with the sleeve already fitted.

– Check the worm and replace if

necessary.

81MS 240, MS 260, MS 260 C

Page 83

13.5 Adjustable Oil Pump

– Troubleshooting, b 4.3

– Remove the clutch, b 6

– Remove the brake band, b 7.2

– Remove the side plate, b 7.6

TOP

: Remove the cover washer (1).

: Check the worm (1) and driver (2)

and replace if necessary

165RA313 TG

: Remove the ring (1) and washer

(2) – only on adjustable oil pump.

: Take out the screws (arrows).

165RA315 TG

If a new oil pump is installed, worms with the number 1121 640 7100 (arrow) must also be replaced. Worms with the number 1121 640 7102 may be used with the new pump. (The numbers shown are not part numbers.)

165RA316 TG

165RA354 TG

165RA317 TG

: Unscrew the worm (1) with driver

(arrow) from the oil pump.

: Check oil suction hose

connection (arrow) and replace hose if necessary, b 13.2

165RA314 TG

165RA307 TG

: Remove the oil pump and

disconnect the oil delivery hose (arrow).

– Check the oil pump (1) and

replace it if necessary

– Inspect the oil delivery hose and

replace if necessary, b 13.3

82 MS 240, MS 260, MS 260 C

Page 84

13.6 Valve

– Line up the oil pump so that the

intake stub points toward the oil suction hose (arrow).

: Push the oil delivery hose (1) on

to the stub.

165RA318 TG

: Push the worm (1) into the oil

pump.

TOP

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

atmospheric pressure. The valve must be replaced if it is faulty.

– Remove the sprocket cover and

cutting attachment, b 5

165RA321 TG

– Open the oil tank cap and drain

the oil tank.

– Collect chain oil in a clean

container, b 1

165RA021 TG

– Place the oil pump (1) in position.

: Insert screws (arrows) and

tighten them down firmly.

: Fit the washer (1) and ring (2).

Only on adjustable oil pump.

: Fit the cover washer (1) so that

the word "TOP" (arrow) faces outwards.

165RA319 TG

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

– Check adjustment of oil pump

and readjust if necessary, b 13.5

165RA320 TG

: Use a 6 mm drift to carefully

drive the valve out of its seat in the housing and into the oil tank.

: Remove the old valve (1) from

the oil tank.

165RA322 TG

165RA323 TG

83MS 240, MS 260, MS 260 C

Page 85

Check correct installed position.

: Insert the valve in the housing

bore (arrow).

: Use a 6 mm drift to carefully

drive in the new valve from outside – note installed depth.

165RA324 TG

165RA325 TG

219RA479 TG

: Installed depth of new valve:

a = about 2 - 3 mm

– Reassemble all other parts in the

reverse sequence.

84 MS 240, MS 260, MS 260 C

Page 86

14. Fuel System

14.1 Air Filter

Dirty air filters reduce engine power, increase fuel consumption and make starting more difficult. The air filter should be checked when there is a noticeable loss of engine power.

– See also Troubleshooting,

b 4.5, b 4.6

: Turn twist lock (1)

counterclockwise.

14.2 Removing and Installing the Carburetor

– Remove the air filter, b 14.1

– Open the fuel tank cap and drain

the fuel tank.

– Collect the fuel in a clean

container, b 1

Pull off the carburetor only when the tank cap is open.

165RA167 TG

165RA327 TG

: Unscrew the nuts (arrows).

Versions with handle and carburetor heating

165RA282 TG

– Remove the carburetor box

cover (2).

– Removing and installing the air

filter – see instruction manual.

– Reassemble in the reverse

sequence.

– Remove the handle molding,

b 12.2

: Disconnect the throttle rod (1)

from the trigger (2).

165RA466 TG

: Remove the fuel hose (1).

: Remove connector (arrow) from

contact spring.

165RA326 TG

: Remove the heating plate (1) and

heating element (2).

– Remove the carburetor, check it

and service or replace if necessary.

165RA328 TG165RA329 TG

– Check the throttle rod and

replace if necessary, b 14.6

85MS 240, MS 260, MS 260 C

Page 87

carburetor heating

Versions with handle and

– Fit the handle molding, b 12.2

– Check operation.

Check that the sleeve (2) and washer (1) are in place.

The throttle rod must be attached to the carburetor.

165RA100 TG

: Fit the heating element (1) and

heating plate (2).

– Fit the nuts and tighten them

down firmly.

– Position the wires, b 15.8

165RA331 TG

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

14.3 Leakage Test

165RA333 TG

In the case of problems with the carburetor or fuel supply system, also check and clean or replace the tank vent, b 14.7

The carburetor can be tested for leaks with the pump 0000 850 1300.

– Remove the carburetor, b 14.2

– Push the carburetor into position.

– Make sure the stub (1) slips into

the impulse hose (arrow).

: Push the fuel hose (1) on to the

stub (arrow).

: Push the connector (1) on to the

contact spring (arrow) as far as stop.

165RA332 TG

: Attach the throttle rod (1) to the

trigger (2).

165RA488 TG

: Push the fuel hose (1)

1110 141 8600 on to the nipple (2) 0000 855 9200.

165RA335 TG

165RA336 TG

86 MS 240, MS 260, MS 260 C

Page 88

: Push the fuel hose with nipple

onto the carburetor’s fuel stub (arrow).

– Push the pressure hose of pump

0000 850 1300 on to the nipple.

: Push the ring (1) to the right and

pump air into the carburetor until the pressure gauge (2) indicates a pressure of about 0.8 bar (80 kPa).

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

1. The inlet needle is not sealing

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

165RA337 TG

Remove to clean, b 14.4.1

2. Metering diaphragm or gasket

damaged, replace if necessary, b 14.4

3. Pump diaphragm or

gasket damaged, replace if necessary, b 14.4.3

– After completing the test, push

the ring (1) to the left to vent the system and then pull the fuel hose off the carburetor.

– Install the carburetor, b 14.2

165RA338 TG

– Tightening torques, b 3.5

– Reassemble all other parts in the

reverse sequence.

14.4 Servicing the Carburetor

165RA339 TG

– Troubleshooting, b 4.6

– Remove the carburetor, b 14.2

– Disconnect the throttle rod,

b 14.6

: Take out the screws (arrows).

Versions with handle and carburetor heating

1 2

: Remove the retainer (1) and

thermostatic switch (2).

165RA340 TG

87MS 240, MS 260, MS 260 C

Page 89

Versions with handle and carburetor heating

: Remove the end cover (1).

If the gasket and diaphragm are stuck to the carburetor, remove them very carefully.

165RA341 TG

– Note installed positions of

metering diaphragm (2) and gasket (1).

: Place the gasket (1) and

metering diaphragm (2) on the pegs (arrows) and check that the tabs (3) are at the same side as the adjusting screws.

165RA342 TG

2 3

165RA076 TG

: Insert two screws (arrows) to hold

the end cover, gasket and metering diaphragm in position.

: Fit the thermostatic switch (1)

and retainer (2).

165RA344 TG

: Carefully separate the metering

diaphragm (1) and gasket (2).

The diaphragm material is subjected to continuous alternating stresses and eventually shows signs of fatigue, i.e. the diaphragm distorts and swells and has to be replaced.

– Check the metering diaphragm

(1) for signs of damage and wear. Install a new gasket.

– Position the end cover (1) so that

the stub (arrow) points towards the air filter.

: Fit the end cover (1) carefully –

the holes must be in alignment.

165RA343 TG

: Fit the screws (arrows).

– Check position of diaphragm and

gasket, then tighten down all screws firmly in a crosswise pattern..

– Reassemble all other parts in the

reverse sequence.

165RA229 TG

88 MS 240, MS 260, MS 260 C

Page 90

14.4.1 Inlet Needle

– Remove the metering

diaphragm, b 14.4

: If there is an annular indentation

165RA345 TG

(arrow) on the sealing cone of the inlet needle, fit a new inlet needle.

Make sure the spring locates on the control lever’s nipple.

– Press the inlet control lever down

and secure it with the screw.

– Check that inlet control lever

moves freely.

– Install the metering diaphragm,

165RA348 TG

b 14.4

14.4.2 Fixed Jet

: Take out the screw (arrow).

: Pull the inlet control lever (1) with

spindle (2) out of the inlet needle’s groove.

The small spring under the inlet control lever may pop out.

: Fit the inlet needle (1).

165RA345 TG

: Fit the spring (2) in the bore.

213

165RA349 TG

– Remove the metering

diaphragm,

b 14.4

: Unscrew the fixed jet (1) with a

suitable screwdriver.

Take care not to damage the fixed jet (1).

– Check the fixed jet (1) and

replace if necessary

– Reassemble in the reverse

sequence.

165RA351 TG

: Remove the inlet needle (1).

– Remove the spring (2). Inspect

and replace if necessary.

: Position the inlet control lever (3)

with spindle (2) on the spring’s seat (arrow) first, then slide the inlet control lever’s clevis into the

165RA347 TG

groove in the inlet needle (1).

165RA489 TG

89MS 240, MS 260, MS 260 C

Page 91

14.4.3 Pump Diaphragm

– Remove the carburetor, b 14.2

: Take out the screw (arrow).

: Carefully remove the end

cover (1).

: Carefully separate the pump

165RA355 TG

diaphragm (1) and gasket (2).

The diaphragm material is subjected to continuous alternating stresses and eventually shows signs of fatigue, i.e. the diaphragm distorts and swells and has to be replaced.

– Check the pump diaphragm for

signs of damage and wear. Install a new gasket.

– Check fuel strainer for

contamination and damage. Clean or replace if necessary.

165RA356 TG

165RA358 TG

: Fit the gasket (1) so that the tab

(2) is opposite the idle speed screw (3) and is held in position by the pegs (arrows).

: Fit the diaphragm (1) on the

gasket so that the tab (2) is opposite the idle speed screw (3) and is held in position by the pegs (arrows).

165RA360 TG

165RA361 TG

165RA359 TG

: Use a needle to remove the fuel

strainer (1) from the carburetor

165RA357 TG

body.

: Carefully remove the gasket with

pump diaphragm from the end cover.

– Reassemble in the reverse

sequence.

90 MS 240, MS 260, MS 260 C

Page 92

14.4.4 Choke Shaft / Choke Shutter

– Position the end cover (1) so that

the idle speed screw (arrow) is at the same side as the adjusting screws.

: Place the end cover (1) against

the carburetor body from below so that the gasket and pump diaphragm are still held in position.

– Align the end cover (1) so that its

pegs engage the holes in the carburetor body.

The choke shutter is in the air filter – see chapter on 'Air Filter' and instruction manual.

14.4.5 Adjusting Screws

165RA362 TG

Grommets have been removed for the sake of clarity.

There are three adjusting screws on the carburetor:

H = high speed screw (1) L = low speed screw (2) LA = idle speed screw (3)

: Pull off the grommets (1 and 2).

Low speed screw

165RA364 TG

: Take out the low speed screw (1).

165RA365 TG

165RA366 TG

– Check that diaphragm and

gasket are properly seated.

: Insert screw and tighten it down

firmly.

– Reassemble all other parts in the

reverse sequence.

If the carburetor cannot be adjusted properly, the problem may be the adjusting screws.

The high speed screw H has a limiter cap, which has to be removed before the screw is

165RA363 TG

removed.

Always install a new limiter cap.

– Remove the carburetor, b 14.2

– See also carburetor

troubleshooting, b 4.6

1 2

– Inspect the sealing ring (1),

washer (2) and spring and replace if necessary.

: Inspect the tip (arrow) for

damage or wear and replace the screw (L) if necessary.

– Screw down the low speed screw

(L) as far as stop.

– Continue with high speed screw.

165RA367 TG

91MS 240, MS 260, MS 260 C

Page 93

High speed screw

: Screw the puller (1) 5910 890

4500 counterclockwise into the limiter cap – left-hand thread.

: Inspect the tip (arrow) for

165RA368 TG

damage or wear and replace the screw (H) if necessary.

– Screw down the high speed

screw (H) as far as stop.

14.5 Adjusting the Carburetor

14.5.1 Basic Setting

The basic setting is necessary only if the high speed screw (H) or low speed screw (L) has to be replaced or after cleaning and adjusting the carburetor from scratch.

165RA371 TG

It is necessary to carry out the basic setting after removing the limiter cap.

The carburetor and air filter are installed, the adjusting screws fitted and the new limiter cap preinstalled.

: Rotate the limiter cap until the lug

(2) is in line with the slot (1).

: Pull out the limiter cap (1).

– Take out the high speed

screw (H).

– Continue with installing limiter

cap.

Pre-installing limiter cap

165RA369 TG

: Push the new limiter cap (1) on to

the high speed screw (H) as far as the detent (arrow) – do not push it fully home.

The basic setting with the preinstalled limiter cap is carried out with screwdriver

165RA370 TG

5910 890 2304.

– Reassemble in the reverse

sequence.

– Carry out basic setting, b 14.5.1

– Check chain tension and adjust if

necessary.

– Inspect the spark arresting

screen (if fitted) and clean or replace if necessary. b 8.1

– Check the air filter and clean or

replace if necessary, b 14.1

– Starting with the low speed and

high speed screws against their seats, turn them 1 full turn counterclockwise.

– Allow engine to warm up.

165RA372 TG

Setting disk 5910 893 6600 may be fitted on the screwdriver 5910 890 2305 to simplify adjustments.

Always install a new limiter cap.

92 MS 240, MS 260, MS 260 C

Page 94

: Push the screwdriver (1)

5910 890 2304 through the opening (arrow) and the preinstalled limiter cap and into the high speed screw – the low speed screw does not have a limiter cap and can be adjusted with screwdriver 5910 890 2305.

Adjust idle speed with a tachometer. Adjust specified engine speeds within tolerance of ± 200 rpm.

1. Adjust engine speed with idle speed screw (LA) to 3,600 rpm.

2. Turn the low speed screw (L) clockwise or counterclockwise to obtain the maximum engine speed.

On machines with a catalytic converter, make sure the engine speeds do not drop below the minimums specified, b 3.1.

165RA373 TG

: Push a suitable drift through the

opening (arrow) and push home the limiter cap until it is flush with the carburetor body.

The basic setting of the high speed screw (H) is now fixed.

This completes the basic setting of the high speed screw (H) and the low speed screw (L).

14.5.2 Standard Setting

– Troubleshooting, b 4.6

– Check chain tension and readjust

if necessary (see MS 240, 260 instruction manual).

– Inspect the spark arresting

screen (if fitted) and clean or replace if necessary. b 8.1

– Check the air filter and clean or

replace if necessary, b 14.1

Standard Setting

165RA374 TG

– Shut down the engine.

– Turn the high speed screw (H)

slowly counterclockwise as far as stop, but not more than a 3/4 turn.

– Turn the low speed screw (L)

slowly clockwise as far as stop, then turn it back 1 full turn.

Check running behavior: The engine must idle and accelerate smoothly.

Adjusting engine idle speed

If this speed is higher than 3,700 rpm, abort the procedure and start again with step 1.

3. Use the idle speed screw (LA) to set engine speed again to 3,300 rpm.

4. Set the engine speed to 2,800 rpm with the low speed screw (L) .

5. Set maximum engine speed with the high speed screw (H) (see Specifications), b 3

The limiter cap must not be removed for the standard setting.

Always perform the following steps before carrying out any adjustments:

– Carry out standard setting.

– Allow engine to warm up.

Engine stalls at idle speed

– Turn the idle speed screw (LA)

clockwise as far as stop or until

165RA375 TG

the saw chain begins to move. Then turn it back one quarter turn.

93MS 240, MS 260, MS 260 C

Page 95

Saw chain rotates at idle speed

– Turn the idle speed screw (LA)

counterclockwise until the chain stops running, then turn it back one quarter turn.

Erratic idling behavior, poor acceleration

(although standard setting is correct)

If the adjustments produce no improvement, see the troubleshooting charts for the ignition system, carburetor and engine, b 4.5, b 4.6 and b 4.7

14.6 Throttle Rod

14.6.1 Removing and Installing the Intake Manifold

A damaged intake manifold can result in engine running problems.

– Troubleshooting, b 4.6 or

b 4.7

– Remove the shroud, b 8.4

Idle setting too lean.

– Allow engine to warm up.

– Turn low speed screw (L)

counterclockwise until the engine runs and accelerates smoothly.

It is usually necessary to change the setting of the idle speed screw (LA) after every correction to the low speed screw (L).

Adjustment for operation at high altitude

A minor correction may be necessary if engine power is not satisfactory when operating at high altitude.

– Check standard setting.

– Allow engine to warm up.

– Turn the high speed screw (H)

clockwise (leaner) – no further than stop.

Turn the adjusting screws only very slightly. Even minor adjustments can noticeably affect engine running behavior.

– Remove the carburetor, b 14.2

: Turn the throttle trigger (1)

slightly and disconnect the throttle rod (2).

– Check the throttle rod and

replace if necessary

– Reassemble in the reverse

sequence.

– Turn the throttle trigger (1)

slightly and attach the throttle rod (2).

– Install the carburetor, b 14.2

– Reassemble all other parts in the

reverse sequence.

– Remove the carburetor, b 14.2

– Take out the annular buffer/tank

housing mounting screws. Annular buffer at ignition side, b 11.3. Annular buffer at clutch side, b 11.2

165RA376 TG

165RA385 TG

: Remove the washer (1) and ring

(2).

If the setting is made too lean there is a risk of engine damage as a result of lack of lubrication and overheating.

94 MS 240, MS 260, MS 260 C

Page 96

: Press the tank housing (1) down

slightly and push the manifold flange (2) out of the tank housing in the direction of the cylinder.

– Pull the impulse hose off the

connector.

: Loosen and remove the hose

clamp (1).

– Pull off the intake manifold (2).

– Inspect the intake manifold (2)

and replace it if necessary – even very minor damage can result in engine running problems, b 4.7

165RA379 TG

: Push the impulse hose (1) on to

the connector (arrow).

: To pull the manifold flange

through the intake opening in the tank housing, wind a piece of string (1) (about 15 cm long)

165RA380 TG

around the back of the flange and pass the ends of the string through the opening.

– Position the manifold flange

against the tank housing.

165RA381 TG

: Pull the ends of the string with the

manifold flange through the opening.

This method ensures that the manifold flange is pulled into place without any damage.

165RA382 TG

– Remove the string.

: Fit the washer (1) and ring (2).

When reassembling, check that all wires are properly seated in their guides.

– Reassemble all other parts in the

reverse sequence.

165RA383 TG

165RA384 TG

– Coat the manifold flange (2) with

STIHL press fluid, b 17

– Push on the intake manifold (2)

position, line it up and secure it in position, b 8.6

– Tightening torques, b 3.5

95MS 240, MS 260, MS 260 C

Page 97

14.6.2 Impulse Hose

A damaged impulse hose can result in engine running problems.

– Remove the carburetor, b 14.2

– Take out the annular buffer/tank

housing mounting screws. Annular buffer at ignition side, b 11.3. Annular buffer at clutch side, b 11.2

– Push the manifold flange out of

the tank housing, and lower the tank housing slightly, b 14.6.1

: Pull the impulse hose (1) out of

165RA386 TG

the tank housing in the direction of the throttle trigger.

– Check the impulse hose (1) and

replace if necessary

: Push the impulse hose (1)

through the opening (arrow) and pull it in until its rubber lip is properly seated.

165RA388 TG165RA389 TG

: Push the impulse hose (1) on to

the connector (arrow).

– Reassemble all other parts in the

reverse sequence.

14.7 Tank Vent

14.7.1 Testing

If problems occur on the carburetor or the fuel supply system, also check and clean the tank vent and replace it if necessary. Check function by performing pressure and vacuum tests on the tank via the fuel hose.

– Open the fuel tank cap and drain

the fuel tank.

– Collect the fuel in a clean

container, b 1

165RA096 TG

– Coat with STIHL press fluid,

b 17

165RA387 TG

– Close the tank cap.

: Pull the impulse hose (1) off the

connector (arrow).

96 MS 240, MS 260, MS 260 C

Page 98

Equalization of pressure takes

14.7.2 Removing and Installing

place via the tank vent. There must be no buildup of vacuum in the tank.

– Clean the area around the tank

vent.

– If necessary, install a new tank

vent or tank, b 14.7 or b 14.8.3

165RA390 TG

: Pull the fuel hose (1) off the stub

(arrow).

: Push the nipple (1)

0000 855 9200 into the fuel hose (arrow).

Vacuum test

Pressure test

: Push the ring (1) to the right and

165RA391 TG

connect the pump (2) 0000 850 1300 to the nipple (arrow) – pressurize the fuel tank.

– Operate the pump (2) until the

pressure gauge indicates a pressure of 0.5 bar. If this pressure remains constant for at least 20 seconds, the tank, including the tank vent, is airtight. If the pressure drops, the leak must be located and the faulty part replaced.

165RA394 TG

– Remove the carburetor box

cover, b 9.2.1

: Pry out the tank vent (1) at the

recess (arrow).

Always install a new tank vent.

– Coat sealing ring of new tank

165RA393 TG

vent (1) with STIHL press fluid, b 17

– Press the new tank vent (1) into

the bore as far as stop.

– Reassemble all other parts in the

reverse sequence.

: Push the ring (1) to the left and

connect the pump (2) 0000 850 1300 to the nipple (arrow) – subject the fuel tank to a vacuum.

– Reassemble in the reverse

sequence.

165RA392 TG

97MS 240, MS 260, MS 260 C

Page 99

14.8 Fuel Intake

14.8.1 Pickup Body

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.

165RA395 TG

165RA397 TG

In the event of problems with the fuel supply system, always check the fuel tank and the pickup body first.

– Troubleshooting, b 4.6 or

b 4.7

Clean the fuel tank if necessary,

– Open the tank 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.

– Dispose of fuel properly in

accordance with environmental requirements, b 1

Use only unleaded fuel in machines with a catalytic converter.

– Open the tank cap.

: Use hook 5910 893 8800 to

remove the pickup body (1) from the fuel tank.

Do not overstretch the fuel hose.

14.8.2 Fuel Suction Hose

– Remove the carburetor, b 14.2

– Remove the pickup body,

b 14.8.1

: Check the fuel hose and replace

if necessary.

165RA398 TG

: Push the fuel hose (1) through

the hole (arrow) in the fuel tank.

165RA396 TG

: Pull the fuel suction hose (1) out

of the fuel tank.

: Line up the fuel hose (1) and

push it into the housing bore – the flange must butt against the rib (arrow).

– Coat with STIHL press fluid,

b 17

98 MS 240, MS 260, MS 260 C

165RA399 TG

Page 100

– Push the manifold flange out of

the tank housing and pull the impulse hose off the connector, b 14.6.2

– Remove the control levers,

b 12

– Remove the short circuit wire,

b 9.6.2

165RA400 TG

165RA402 TG

: Use hook 5910 893 8800 to pull

the fuel hose (1) out of the fuel tank.

Do not overstretch the fuel hose.

– Fit the pickup body, b 14.8.1

– Close the tank cap.

14.8.3 Removing and Installing the Tank Housing

If a mounting thread for plastic tapping screws is damaged, the tank housing can be repaired by fitting a thread insert.

– Drain the fuel tank, b 1

– Remove the handlebar, b 11.5

or b 11. 6

– Remove the carburetor,

b 14.2

Use only unleaded fuel in machines with a catalytic converter.

Versions with handle heating

– Remove the wiring harness,

b 15.8

– Remove the handle heating

system, b 15.3

: Pull out the tank housing (1).

– Inspect the tank housing and

replace if necessary

Only transfer those parts from the old tank housing that are not included with the replacement – see parts list.

: Fit the front end (2) of the tank

housing (1) between the two halves of the crankcase and line it up with annular buffer bores.

– Insert the annular buffer/chain

catcher mounting screw.

– Reassemble all other parts in the

reverse sequence.

– Tightening torques, b 3.5

165RA401 TG

– Take out the annular buffer/tank

housing mounting screws. Annular buffer at ignition side, b 11.3. Annular buffer at clutch side, b 11.2 Annular buffer/chain catcher, b 11.1

99MS 240, MS 260, MS 260 C

Stihl MS 240, MS 260 Instruction Manual

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

1. Introduction

2. Safety Precautions

3. Specifications

3.1 Engine

3.2 Fuel System

3.3 Ignition System

3.4 Chain Lubrication

3.5 Tightening Torquese

4. Troubleshooting

4.1 Clutch

4.2 Chain Drive, Chain Brake, Chain Tensioner

4.3 Chain Lubrication

4.4 Rewind Starter

4.5 Ignition System

4.6 Carburetor

4.7 Engine

5. Cutting Attachment

5.1 Chain Catcher

6. Clutch

6.1 Clutch Drum

7. Chain Brake

7.1 Checking Operation

7.2 Removing and Installing the Brake Band

7.3 Brake Lever

7.4 Cam Lever

7.5 Pins

7.6 Side Chain Tensioner

7.6.1 Front Chain Tensioner

7.6.2 Quick Chain Tensioner

7.7 Bar Mounting Studs

8. Engine

8.1 Muffler / Spark Arresting Screen

8.2 Leakage Test

8.2.1 Preparations

8.2.2 Vacuum Test

8.2.3 Pressure Test

8.3 Oil Seals

8.4 Removing and Installing the Shroud

8.5 Cylinder

8.6 Crankshaft

8.6.1 Removing and Installing

8.6.2 Bearings / Crankcase

8.7 Piston

8.7.1 Removal

8.7.2 Installing

8.8 Piston Rings

8.9 Decompression Valve

9. Ignition System

9.2 Ignition Module

9.2.1 Removing and Installing

9.1 Ignition Timing

9.3 Testing the Ignition Module

9.4 Spark Plug Boot / Ignition Lead

9.5 Flywheel

9.6 Short Circuit Wire

9.6.1 Testing

9.6.2 Removing and Installing

9.6.3 Ground Wire

9.7 Ignition System Troubleshooting

10. Rewind Starter

10.1 General

10.2 Removing and Installing

10.3 Pawl

10.4 Rope Rotor

10.5 Starter Rope / Grip

11. Servicing the AV System

11.1 Annular Buffer on Chain Catcher

11.2 Annular Buffer at Clutch Side

11.3 Annular Buffer at Ignition Side

11.5 Handlebar

11.4 Stop Buffer

11.6 Handlebar with Handle Heating

12. Control Levers

12.1 Switch Shaft

12.1.1 Removing and Installing