Stihl MS 241 User Manual

STIH)

STIHL MS 241 C

2010-11

1. Introduction and safety precautions 3

1.1 Introduction 3

1.2 Safety precautions 4

2. Specifications 5

2.1 Engine 5

2.2 Fuel system 5

2.3 Ignition system 5

2.4 Chain lubrication 5

2.5 Tightening torques 6

3. Troubleshooting 8

3.1 Clutch 8

3.2 Chain Drive, Chain Brake, Chain Tensioner 9

3.3 Chain lubrication 11

3.4 Starter 12

3.5 Ignition system 14

3.6 Carburetor 15

3.7 Engine 18

4. Clutch 19

4.1 Clutch drum 19

4.2 Clutch 19

5. Chain brake 20

5.1 Checking operation of chain brake 20

5.2 Brake band 20

5.3 Brake lever 21

5.4 QuickStop Super brake lever 23

5.4.1 Adjusting brake cable 25

5.4.2 Brake cable Removal and installation 27

5.5 Cam lever 28

5.6 Pins 29

5.7 Chain tensioner 31

5.7.1 Quick chain tensioner 31

5.7.2 Chain catcher 32

5.8 Bar mounting stud 32

5.9 Collar nut for chain sprocket cover 32

6. Engine 34

6.1 Muffler 34

6.2 Leak testing 35

6.2.1 Preparations 35

6.2.2 Vacuum test 36

6.2.3 Pressure test 36

6.3 Oil seals 37

6.3.1 Ignition side 37

6.3.2 Clutch side 37

6.4 Shroud 38

6.5 Cylinder 39

6.6 Crankshaft 41

6.6.1 Ball bearing / crankcase 46

6.7 Piston 47

6.8 Piston rings 49

6.9 Decompression valve 50

7. Ignition system 51

7.1 Ignition timing 51

7.2 Pre-separator 51

7.3 Control unit 51

7.4 Spark test check control unit 54

7.5 Spark plug boot 55

7.5.1 Ignition lead 56

7.6 Flywheel 56

7.7 Short circuit wire 57

7.7.1 Contact test 57

7.7.2 Removal and installation 57

7.7.3 Ground wire 64

7.7.4 Contact spring 64

7.8 Troubleshooting, ignition system 66

8. M-Tronic 69

8.1 Calibrating the control unit 69

8.2 Testing 70

8.2.1 Test preparations 70

8.2.2 Connect the test lead 70

8.2.3 Check screwed and plug connections as well as switch 70

8.2.4 Checking the solenoid valve 72

8.2.5 Checking the start detection function 73

8.2.6 Checking the wiring harness 74

8.3 Wiring harness 76

8.4 Switchgear 76

8.5 Troubleshooting, M-Tronic 80

8.5.1 Engine does not start 80

8.5.2 Engine does not start in position } 81

8.5.3 Engine speed drops under load – low power 82

8.5.4 Ignition – no ignition spark 83

8.5.5 Engine stops suddenly 84

8.5.6 Cut-off speed not reached 85

9. Rewind starter 86

9.1 General 86

9.2 Fan housing 86

9.3 Pawls 87

9.4 ErgoStart 88

9.5 Rope rotor 89

9.6 Starter rope / starter grip 89

9.7 Tensioning the rewind spring 90

9.8 Replacing the rewind Spring 91

RA_741_00_01_01

1MS 241 C

Contents

10. Maintaining the antivibration elements 94

10.1 Antivibration element on oil tank 94

10.2 Antivibration element on fuel tank 94

10.3 Antivibration element on front handle 96

10.3.1 Antivibration element on handlebar, version with heating 97

10.3.2 Stop buffer 98

10.3.3 Filter base buffers 98

10.4 Front handle 99

10.4.1 Handlebar with heating 100

11. Actuating levers 105

11.1 Master Control lever 105

11.1.1 Removal and installation 105

11.2 Throttle trigger / throttle trigger interlock 106

11.3 Throttle trigger / throttle trigger interlock / QuickStop Super 107

11.3.1 Trigger switch QuickStop Super 108

11.3.2 Trigger interlock QuickStop Super 109

11.4 Choke rod 110

11.5 Throttle rod 110

12. Chain lubrication 112

13. Fuel system 115

13.1 Air filter 115

13.2 Baffle 115

13.3 Filter base 115

13.4 Air guide shroud 117

13.4.1 Air guide shroud, versions with manual fuel pump 120

13.4.2 Air guide shroud version with heating 123

13.5 Carburetor 129

13.5.1 Leakage test 133

13.6 Repairing the carburetor 133

13.6.1 Metering diaphragm 134

13.6.2 Inlet needle 135

13.6.3 Pump diaphragm 135

13.6.4 Lead retainer 137

13.6.5 Lever of the throttle shaft 137

13.6.6 Lever of the choke shaft 138

13.7 Carburetor adjustment 138

13.8 Carburetor bracket 138

13.9 Intake elbow 140

13.10 Tank vent 141

13.10.1 Testing 141

13.10.2 Removal and installation 142

13.11 Fuel intake 143

13.11.1 Pickup body 143

13.11.2 Fuel hose 143

13.11.3 Fuel hoses manual fuel pump 146

13.11.4 Manual fuel pump 148

13.11.5 Tank housing 149

14. Heating 152

14.1 Carburetor heating 152

14.1.1 Check overall system 152

14.1.2 Check heating element 152

14.1.3 Thermostatic switch 153

14.2 Troubleshooting, carburetor heating 154

14.3 Handle heating systems 155

14.3.1 Troubleshooting 155

14.4 Heating switch 156

14.5 Heating element in handle 158

14.6 Heating element in front handle 159

14.7 Generator 160

14.7.1 Troubleshooting chart, handle heating systems and generator 162

14.7.2 Summary of test connections and test values 164

14.8 Wiring harness 166

14.9 Connecting leads heating elements 167

15. Special tools 170

16. Service accessories 172

12.1 Pickup body 112

12.2 Oil suction hose 112

12.3 Oil pump 112

12.4 Valve 114

2 MS 241 C

1. Introduction and safety precautions

1.1 Introduction

This Service Manual contains detailed descriptions of all the typical repair and servicing procedures for this machine.

Refer to the illustrated spare parts lists during all repair work. These lists show the installation position and order in which the individual parts and modules should be assembled.

Refer to the latest edition of the relevant spare parts list to check the part numbers of any spare parts required.

A fault on the machine may be due to several causes. To help locate the fault, consult the chapter on "Troubleshooting" and the "STIHL Service Training System" for all functional groups.

The special tools mentioned in the descriptions are listed in the chapter "Special Servicing Tools" of this manual. The tools can be identified according to part number in the "STIHL Special Tools" manual. The manual lists all tools supplied by STIHL.

Symbols are included in the text and pictures for greater clarity. The meanings are as follows:

In the text:

N Action to be taken as shown in

the illustration above the text

– Action to be taken that is not

shown in the illustration above the text

In the illustrations:

A Item pointer (short)

2710RA320 TG

Servicing and repairs are made considerably easier if the machine is mounted on assembly stand (3) 5910 890 3101. For this purpose, secure the clamp (2) 5910 850 1650 to the assembly stand with two screws (1).

The screws must not protrude, as they may damage the housings when clamping the machine, depending on the machine.

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 spare parts list and Service Manual until an updated edition is issued.

a Direction of

movement (long arrow)

@ 4.2 Reference to another

chapter, in this case to Chapter 4.2

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

2410RA000 TG

The machine is guided with the collar screw through the upper hole of the clamping rail and fastened using nut M 8 (arrow).

The machine is fastened to the mount on the clamping rail by the screw head on the crankcase.

3MS 241 C

Preparing to make repairs

Before repair tasks or clamping on the assembly stand, always remove the chain sprocket cover, saw chain and guide bar.

Always use original STIHL replacement parts. They can be identified by the STIHL part number the logo { and the STIHL parts symbol K The symbol may appear alone on small parts.

Storage or disposal of oil and fuel

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

Plug connections on electrical leads

1.2 Safety precautions

Specific national safety regulations and the safety instructions in the instruction manual must be observed if the machine has to be started up during maintenance or repair work.

Gasoline is highly inflammable and can also be explosive under certain conditions.

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

Test for leakage after all work on the fuel system and engine.

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.

Suitable gloves must be worn without fail if parts are heated for assembly/disassembly purposes.

Improper handling may result in burns and other serious injuries.

The chapter "Tightening Torques" lists all components of this machine that must be tightened with the specified tightening torques or coated with thread-locking adhesive. These specifications must be observed throughout the Service Manual when tightening screws and nuts as well as other fasteners.

Fuel system – barbed connectors

Pull or push the fuel hoses, by hand whenever possible, in the direction of the connector in order to ensure leakproofness of the fuel system.

Avoid damaging the barbed connectors – sharp-edged pliers, screwdrivers, etc., may not be used. Also, do not cut open fuel hoses with a knife or similar aids.

Do not reuse fuel hoses after disassembly, but instead always replace them with new hoses – fuel hoses can be overstretched when being detached.

Mount new fuel hoses dry or using STIHL press fluid, b 16.

The insulating tube must be oriented so that it is centered over the plug connection and completely enclose the plug connection – danger of short-circuiting.

The plug connection is completely plugged together when it has a total length of a = max. 30 mm.

Always replace damaged parts. Check dismantled parts for wear and damage before installation, replace if necessary.

5902RA299 TG

Only use the machine with the shroud mounted – otherwise the rotating fan wheel poses a risk of injury and there is a risk of engine damage due to overheating.

Other press fluids are not permitted and may lead to fuel hose damage.

When using STIHL press fluid, apply press fluid to the ends of the hose and the connectors and press the new hoses onto the barbed connectors, b 16.

4 MS 241 C

2. Specifications

2.1 Engine

MS 241 C

Displacement: 42.6 cm

Bore: 42.5 mm Stroke: 30.0 mm Engine power to ISO 7293: 2.2 kW (3.0 HP)

at 10000 rpm

Max. permissible engine speed (with bar and chain): 14000 rpm

Idle speed: 2800 rpm Clutch: Centrifugal clutch without

linings Clutch engages at: 3500 rpm Crankcase leakage test at gauge pressure: p under vacuum p

= 0.5 bar

2.2 Fuel system

Carburetor leakage test at

gauge pressure: p

Operation of tank vent at

gauge pressure: p

Fuel: as specified in instruction

= 0.8 bar

= 0.5 bar

manual

2.3 Ignition system

2.4 Chain lubrication

Air gap between control unit

and fanwheel: 0.30 (+ 0.05/- 0.10) mm

Spark plug (suppressed): NGK CMR 6 H

Electrode gap: 0.5 mm

Speed-controlled oil pump with reciprocating piston and

manual oil flow control

Oil flow settings:

min:

4.0 (+/- 2.0) cm

/min

at 7000 rpm

max:

8.0 (+/- 3.0) cm

/min

at 7000 rpm

5MS 241 C

2.5 Tightening torques

DG and P screws are fitted in plastic and light alloy metal parts. These screws form a permanent thread when they are installed for the first time. The material is permanently deformed. Screws can be removed and installed as often as necessary without impairing the strength of the screwed assembly, provided that the specified tightening torque is observed. For this reason it is essential to use a torque wrench.

Fastener Thread size For component Tightening

torque Nm

Screw P 4x12 Cover plate / fan housing 2.0 Screw P 4x10 Cover / tank housing 1.0 Screw D 4x12 Cover / chain tensioner / crankcase 2.5 2), 4) Screw M 5x16 Antivibration element / crankcase 8.0 2), 4) Screw P 5x34 Antivibration element / tank housing 4.0 Screw D 4x12 Brake band / crankcase 3.0 2), 4) Screw P 4x10 Brake cable support / tank housing 1.0 Q Stud M 5x18 Stud 7.0 2), 3) Stud M 8 Bar mounting stud 23.0 1) Stud M 8 Bar mounting stud 23.0 1), B Stud D 8x18 Bar mounting stud (repair solution) 16.0 Screw D 4x12 Cover, chain brake / crankcase 3.0 2), 4)

M 10x1 Decompression valve 14.0 Nut M 5 Filter base / baffle / carburetor 3.5 Screw M 4x12 Generator / crankcase 3.0 3), VW Screw P 6x25 Handlebar / locking screw 8.0 VW Screw P 6x26.5 Handlebar / tank housing right 6.0 Screw P 6x30 Handlebar / tank housing right 6.0 2), 4), VW Screw M 5x16 Handlebar / tank housing bottom 5.0 2), 3) Screw M 5x12 Handlebar / tank housing bottom 8.0 3), VW Screw M 5x16 Handlebar / plugs antivibration springs 10.0 2), 3), VW Screw M 5x20 Hand guard / fan housing / crankcase 6.0 3) Screw P 6x30 Chain catcher / crankcase / bearing plugs 6.0 Nut M 5 Spiked bumper / crankcase / upper lock nut 8.0 Screw M 5x10 Spiked bumper / top of crankcase 8.0 2), 3) Screw M 5x16 Spiked bumper / bottom of crankcase 8.0 2), 3) Screw D 4x12 Manifold / cylinder 4.0 2), 4) Screw M 5x20 Crankcase drive side / fan side 10.0 2), 4) Screw M 5x16 Bearing plugs / cylinder 10.0 2), 3) Screw M 5x16 Fan housing / crankcase 6.0 2), 4) Screw D 4x12 Air guide shroud / crankcase 4.0 2), 4)

Comment

6 MS 241 C

Fastener Thread size For component Tightening

torque Nm

Carrier M 12x1 L Crankshaft carrier 50.0 Screw D 4x12 Oil pump / crankcase 4.0 2), 4) Screw M 5x16 Muffler / crankcase 10.0 2), 3) Screw M 5x16 Muffler / cylinder 10.0 2), 3) Nut M 8x1 Flywheel / crankshaft 28.0 5) Nut M 12x0.75 Switch 2.0 Screw P 4x10 Support 1.0 Screw D 4x12 Pre-separator / crankcase 4.0 2), 4)

M 10x1 Spark plug / cylinder 12.0 Screw D 4x20 Control unit / cylinder 4.5 2), 4) Screw M 5x20 Cylinder / crankcase 1st stage 4.0 2), 4) Screw M 5x20 Cylinder / crankcase 2nd stage 10.0 2), 4)

Remarks:

1) Loctite 242 or 243 medium strength

2) Screws with locking serration

3) Microencapsulated screws

4) Screws with easy-slide coating

5) Connection between crankshaft and flywheel must be degreased and oil-free Q) QuickStop Super B) Quick chain tensioner VW) Heating

Comment

When inserting DG and P screws into an existing screw thread:

Insert the DG or P screw in the hole and turn counterclockwise until it gently drops into the hole in axial direction. 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 Loctite 242 or 243 medium strength before refitting them.

Screwdriver speed when used in plastic material: max. 500 rpm for DG and P-type screws. Do not use an impact wrench to release or tighten screw connections.

Screws with and without locking serration must not be confused.

7MS 241 C

3. Troubleshooting

3.1 Clutch

Problem Cause Remedy

Saw chain becomes stuck under full load

Saw chain rotates at idle speed Idle speed too high Check M-Tronic

Loud noises Tension springs stretched Replace all tension springs

Clutch shoes badly worn Install new clutch

Clutch drum badly worn Install new clutch drum

Tension springs of the clutch shoes are stretched

Tension springs of the clutch shoes are broken

Needle cage damaged Replace needle cage

Clutch shoe retainer broken Examine retainer, replace if

Replace tension springs, replace clutch if necessary

Replace tension springs

necessary

Clutch shoes and carrier worn Install new clutch

8 MS 241 C

3.2 Chain Drive, Chain Brake, Chain Tensioner

Problem 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

Saw chain becomes stuck under full load

Saw chain rotates at idle speed Idle speed too high Check M-Tronic

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 stuck Check freedom of movement and

function of brake band

Tension springs of the clutch shoes are stretched

Tension springs of the clutch shoes are broken

Brake spring stretched or broken Fit new brake spring

Replace tension springs, replace clutch if necessary

Replace tension springs

Brake band stretched, worn or broken

Clutch drum worn Install new clutch drum

Fit new brake band

9MS 241 C

Problem Cause Remedy

QuickStop Super

Coasting brake is not released although trigger interlock is pressed

QuickStop Super

Brake band is not released although trigger interlock is pressed

QuickStop Super

Coasting brake does not brake properly – trigger interlock not pressed

Brake cable stretched Adjust brake cable

Brake cable unhooked or broken Reattach or replace brake cable

Excessive play on trigger interlock Adjust brake cable

Brake cable overstretched Adjust brake cable

Sleeve of the brake cable not seated completely in adjusting screw

Push the sleeve into the adjusting screw as far as it will go and adjust brake cable

10 MS 241 C

3.3 Chain lubrication

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

Problem Cause Remedy

Chain receives no oil Oil inlet hole in guide bar is blocked Clean oil inlet hole

Intake hose or pick-up body clogged or intake hose ruptured

Valve in oil tank blocked Clean or replace valve

Worm worn Replace worm

Oil pump damaged or worn Install new oil pump

Machine looses chain oil Oil pump damaged or worn Install new oil pump

Oil intake hose connection damaged

Crankcase cracked Check crankcase halves and

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

Worm carrier is loose Replace worm

Fit new intake hose and pick-up body

Fit new oil intake hose

replace damaged crankcase halves

11MS 241 C

3.4 Starter

Problem Cause Remedy

Starter rope broken Rope pulled out too vigorously as

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

Normal wear Replace starter rope

Starter rope does not rewind Heavy fouling or rust on rewind

spring

Spring insufficiently tensioned Check rewind spring and increase

Rewind spring broken Replace rewind spring

Starter rope cannot be pulled out far enough

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

Rewind spring overtensioned Check rewind spring and reduce

Guide peg on pawls or pawls themselves are worn

Replace starter rope

Clean or replace rewind spring

tension

Replace pawls

Spring clip fatigued Replace spring clip

Spring clip improperly installed Install spring clip properly

...Versions with ErgoStart Guide peg on pawls or pawls

themselves are worn

Torsion spring on flywheel are fatigued, pawls are worn or sticking

Lugs on carrier are worn Replace carrier

Anchor loop in spring housing not hooked onto carrier

Starter rope is difficult to pull – versions with ErgoStart

Spring in spring housing is fatigued Replace spring housing

Replace pawls

Clean mounts on the pawls, replace pawls and torsion springs if necessary

Hook anchor loop to carrier

12 MS 241 C

Problem Cause Remedy

Starter rope is difficult to pull or rewinds very slowly

Starter mechanism is very dirty Thoroughly clean complete starter

mechanism

At very low outside temperatures: Lubricant oil on the rewind spring becomes viscous (spring winding stick together) or moisture has penetrated the rewind spring (spring windings are frozen)

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

13MS 241 C

3.5 Ignition system

Problem 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 In the event of repeated sooting, check air filter

Fuel/oil mixture – contains too much oil

Wrong air gap between control unit and flywheel

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

Incorrect ignition timing, flywheel out of adjustment – Key in flywheel has sheared off

Weak magnetization in flywheel Install new flywheel

Use a fuel mixture with the correct mixing ratio

Set the correct air gap

Install new flywheel

Irregular spark Check operation of switch shaft/

contact spring and control unit Damaged insulation or interruption in ignition lead or short circuit wire. Check ignition lead/control unit, replace control unit if necessary. Check operation of spark plug, clean spark plug and replace if necessary. Check M-Tronic

14 MS 241 C

3.6 Carburetor

Problem Cause Remedy

Carburetor floods; engine stalls Inlet needle not sealing

– Foreign matter in valve seat or cone

Inlet needle worn Replace inlet needle

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

Metering diaphragm is deformed Replace metering diaphragm

Poor acceleration Carburetor setting too lean Check M-Tronic

Carburetor setting too rich Check M-Tronic

Remove and clean inlet needle or clean carburetor

Examine control lever, replace if necessary

Remove the inlet control lever and refit it correctly

Replace metering diaphragm

Inlet needle sticking to valve seat Remove inlet needle, clean and

refit

Diaphragm gasket leaking Replace diaphragm gasket

Metering diaphragm damaged or shrunk

Tank vent faulty Replace tank vent

Leak in fuel line between tank and carburetor

Replace metering diaphragm

Seal connections or replace line

15MS 241 C

Problem Cause Remedy

Engine will not idle, idle speed too high

Engine stops when idling Idle jet bores

Throttle shutter is not closed properly when the throttle trigger is not pressed

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

Throttle shutter does not close Replace carburetor

or ports blocked

Idle jet too rich or too lean

Tank vent faulty Replace tank vent

Leak in fuel line between tank and carburetor

Examine carburetor and throttle rod, replace if necessary

if necessary

Clean the carburetor

Check M-Tronic

Seal connections or replace line

Saw chain rotates at idle speed Idle speed too high Check M-Tronic

Clutch springs stretched or fatigued Replace tension springs, replace

clutch if necessary

Anchor loops of the clutch spring hooks are broken

Replace tension springs

16 MS 241 C

Problem Cause Remedy

Engine speed drops quickly under load – low power

Air filter dirty Clean air filter, replace if necessary

Throttle shutter not opened fully Check throttle rod

Tank vent faulty Replace tank vent

Fuel pick-up body dirty Replace pickup body

Fuel strainer dirty Clean fuel strainer in carburetor,

replace if necessary

Leak in fuel line between tank and carburetor

Carburetor setting too lean Check M-Tronic

Main jet bores or ports blocked Clean the carburetor

Pump diaphragm damaged or fatigued

Seal connections or replace line

Replace pump diaphragm

Engine runs extremely rich, lacks power and has very low final speed

Incorrect ignition timing, flywheel out of adjustment – Key in flywheel has sheared off

Choke shutter does not open Examine the carburetor and starter

Carburetor setting too rich Check M-Tronic

Install new flywheel

shaft and repair or replace if necessary

17MS 241 C

3.7 Engine

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

- Air filter,

- Fuel system,

- Carburetor,

- Ignition system

Problem 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 engine defective Replace oil seals

Crankcase leaking or damaged (cracks)

Intake manifold damaged/ hole is plugged

Piston rings worn or broken Replace piston rings

Muffler / spark arresting screen carbonized

Air filter dirty Clean or replace air filter

Fuel line kinked or cracked Replace fuel line and ensure that is

Replace damaged crankcase halves

Clean hole or replace intake manifold

Clean muffler (inlet and outlet openings), replace spark arresting screen, replace muffler if necessary

installed without kinking

Intake manifold damaged / hole is plugged

Engine is overheated Insufficient cylinder cooling. Air

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

Air intake in fan housing is fouled Clean air intake on fan housing

18 MS 241 C

Clean hole or replace intake manifold

Thoroughly clean all cooling air openings and the cylinder fins

4. Clutch

4.1 Clutch drum

– Clutch drum removal and

installation, see Instruction Manual

– Remove needle cage

– Clean needle cage and

crankshaft stub, b 16

– Grease needle cage and

crankshaft stub, b 16

100%

: Remove the spark plug boot (1)

– Unscrew spark plug

2410RA001 TG

: Unscrew the clutch (1) with

hexagon (arrow) – left-hand thread

Installation

TOP

2410RA004 TG

80%

– Examine the clutch drum (1) for

signs of wear

The remaining thickness must be measured if there are distinct signs of wear on the inside diameter of the clutch drum (1). The clutch drum must be replaced if the remaining thickness is less than approx. 80 % of the original thickness.

– Install the clutch drum

4.2 Clutch

– Troubleshooting, b 3.1

– Removing the clutch drum,

b 4.1

– Remove shroud, b 6.4

5902RA018 TG

: Orient the locking strip (1)

0000 893 5904 so that the flat side of the metallic attachment faces the piston and insert it in the cylinder

: Locking strip (1) 0000 893 5904

must rest against the cylinder wall (arrow) and the flat side of the metal attachment must rest against the piston head – Position as shown

2410RA002 TG

2410RA005 TG

Slide washer (1) into place so that the word "TOP" is visible.

: Fit the clutch (2) on the

crankshaft stub so that the raised hexagon (arrow) can be seen

: Screw on and tighten the

clutch (2) – left-handed thread

– Pull the locking strip out of the

cylinder

– Reassemble remaining parts in

2410RA003 TG

reverse order

19MS 241 C

5. Chain brake

5.1 Checking operation of chain brake

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.

Fouling (particularly 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. This in turn extends the braking time. A fatigued or stretched brake spring has the same negative effect.

– Starting the engine

– With the chain brake

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

– With the chain brake released,

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

Versions with QuickStop Super

When the trigger interlock is pressed, the clutch drum must rotate freely.

With the coasting brake released, open the throttle wide and release the trigger interlock in the rear handle – the saw chain must come to an abrupt stop

All versions

The braking time is in order if deceleration of the saw chain is imperceptible to the eye (less than 1 second).

If the chain brake does not operate properly, refer to the troubleshooting chart, b 3.2.

5.2 Brake band

– Remove the clutch drum, b 4.1

– Troubleshooting, b 3.2

: Remove screws (1)

: Remove the cover (2)

– Block chain brake

: Ease brake band (2) out of

guide (arrow)

– Remove brake band, taking care

not to overextend it

– Release the chain brake

: Turn brake band (1) slightly aside

and disconnect it from the brake lever (2)

2410RA006 TG

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

5902RA024 TG

219RA049 TG

2410RA007 TG

: Unscrew screw (1) on the bottom

of the machine

20 MS 241 C

Installation

5.3 Brake lever

– Troubleshooting, b 3.2

– Remove shroud, b 6.4

– Remove fan housing, b 9.2

– Release the chain brake

: Attach brake band (1) to brake

lever (2) sideways and turn it towards its mount

: Insert brake cable (1) in

guide (arrow)

: Push brake band (1) fully home in

2410RA009 TG

the mount (arrow)

: Screw in and tighten screw (2) on

the bottom of the machine

: Insert cover (1)

2410RA010 TG

: Insert and tighten down the

screws (2)

– Remove brake band, b 5.2

2410RA012 TG

– Block chain brake

The brake spring is now relaxed.

: Use the assembly tool

2410RA013 TG

1117 890 0900 to unhook the brake spring (1) at the anchor pin (arrow)

– Unhook and remove the brake

spring at the brake lever

2410RA014 TG

– Block chain brake

: Guide brake band (1) over

studs (arrows) and press it into the mount

– Install the clutch drum, b 4.1

When the chain brake is released, the clutch drum must rotate freely.

– Carry out additional function

tests, b 5.1

– Reassemble remaining parts in

reverse order

2410RA011 TG

21MS 241 C

: Push out circlip (1)

– Examine pins and replace if

necessary, b 5.6

– Check cam on hand guard,

replace hand guard if necessary

Installation

– Clean pins and disassembled

2410RA015 TG

parts, b 16

2410RA020 TG

: Slightly lift up bearing eye of the

– Grease pins, b 16

hand guard (1) and brake lever (2) and guide the parts over the anchor pins (arrows)

: Draw hand guard (1) and brake

lever (2) off the anchor pins (arrows) simultaneously

– Take out hand guard and brake

lever

– Examine cam lever and replace if

necessary, b 5.5

: Pull brake lever (2) out of hand

guard (1)

2410RA016 TG

: Position brake lever (2) so that

mount for brake spring (arrow) is at the top

: Slide brake lever (2) into recess

in hand guard (1) until the holes are lined up

2410RA017 TG

: Slide hand guard (1) with brake

lever (2) across the machine until it rests against the anchor pins (arrows)

2410RA018 TG

: Turn cam lever (1) slightly aside

until cam of hand guard (arrow) slides past

– Press bearing eye of hand guard

and brake lever onto the anchor pins

2410RA019 TG

: Push circlip (1) into place

2410RA021 TG

2410RA022 TG

22 MS 241 C

5902RA040 TG2410RA023 TG

spring at the brake lever

2410RA024 TG

– Unhook and remove the brake

The turns of the brake spring must be tightly spaced when not installed; use a new brake spring if necessary.

– Position the protective tube so

that it starts after the second turn (arrow)

– The pin for the brake spring must

be replaced if it shows signs of wear at the groove, b 5.6

: Hook brake spring (1) into brake

lever (arrow)

: Use the assembly tool (2)

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

– Grease brake lever, cam lever

and hand guard motion link, b 16

– Reassemble remaining parts in

reverse order

5.4 QuickStop Super brake lever

– Troubleshooting, b 3.2

– Remove shroud, b 6.4

– Remove fan housing, b 9.2

– Remove brake band, b 5.2

2410RA026 TG

: Unhook brake spring (1) from

anchor pin (arrow)

: Unhook and remove the brake

spring (1) at the brake lever

2410RA027 TG

: Draw hand guard (1) and brake

lever (2) off the anchor pins (arrows) simultaneously

– Block chain brake

The brake spring is now relaxed.

: Use the assembly tool

1117 890 0900 to unhook the brake spring (1) at the anchor pin (arrow)

– Take out hand guard and brake

lever

2410RA025 TG

23MS 241 C

Installation

– Clean pins and disassembled

parts, b 16

: Disconnect brake cable (1)

: Pull brake lever (2) out of hand

guard (1)

– Examine cam lever and replace if

necessary, b 5.5

– Examine pins and replace if

necessary, b 5.6

– Grease pins, b 16

2410RA028 TG

: Position brake lever (2) so that

mount for brake spring (arrow) is at the top

: Slide brake lever (2) into recess

2410RA029 TG

in hand guard (1) until the holes are lined up

2410RA032 TG

: Slide hand guard (1) with brake

lever (2) across the machine until it rests against the anchor pins (arrows)

2410RA030 TG

2410RA033 TG

: Slightly lift up bearing eye of the

hand guard (1) and brake lever (2)and guide the parts over the anchor pins (arrows)

– Check cam on hand guard,

replace hand guard if necessary

2410RA031 TG

: Attach brake cable (1) to

hole (arrow) in brake lever

24 MS 241 C

: Attach brake spring (1) to anchor

pin (2)

: Turn cam lever (1) aside until

cam of hand guard (arrow) slides past

– Press bearing eye of hand guard

and brake lever onto the anchor pins

: Check seat of the sleeve (1) at

the brake cable, push completely into the hole in the housing (arrow) if necessary

2410RA034 TG2410RA035 TG

The turns of the brake spring must be tightly spaced when not installed; use a new brake spring if necessary.

– Position the protective tube so

that it starts after the second turn (arrow)

– The pin for the brake spring must

be replaced if it shows signs of wear at the groove, b 5.6

: Use the assembly tool

1117 890 0900 to hook the brake

5902RA040 TG

spring (1) onto the anchor pin (arrow)

– Grease brake lever, cam lever

and hand guard motion link, b 16

– Adjust brake cable, b 5.4.1

– Reassemble remaining parts in

reverse order

5.4.1 Adjusting brake cable

If the coasting brake does not operate properly although the brake band is intact, it may be necessary to adjust the brake cable.

– Troubleshooting, b 3.2

– Check condition and play

2410RA025 TG

: Hook brake spring (1) into the

brake lever so that the opening of the anchor loop (arrow) is visible

: Hook brake spring (1) onto brake

lever (arrow)

2410RA036 TG

2410RA037 TG

– Remove chain brake cover,

b 5.2

When the trigger interlock is not pressed, the brake cable must be without tension.

25MS 241 C

Adjust brake cable

: Screw in adjusting screw (2)

– Play increases

– Press and hold the trigger

interlock down completely

Brake band (1) must rest against the crankcase (arrows) without play and the clutch drum must rotate freely.

– Release trigger interlock

2410RA038 TG

: Remove screw (1)

: Lower tank housing (2)

: Unscrew adjusting screw (2)

– Play decreases

: Once play is adjusted correctly,

tighten clamping screw (3)

2410RA039 TG

– Press and hold the trigger

interlock down completely

Brake band (1) must rest against the crankcase (arrows) without play and the clutch drum must rotate freely.

2310RA050 TG

2410RA038 TG

: Press trigger interlock (1) gently

to check the play

– The play must not exceed the

mark (a)

Play: is equal to the distance traveled by the trigger interlock (1) without causing the brake lever to move at the same time.

Play is necessary to ensure trouble free functioning of the coasting brake.

– Troubleshooting, b 3.2

: Loosen clamping screw (1) on

the support for the brake cable

0001RA456 TG

The sleeve (1) must be seated on the adjusting screw (2) as far as it will go.

: Position open-end wrench SW 6

on the adjusting screw (2) and adjust play

– Reassemble remaining parts in

reverse order

2410RA556 TG

26 MS 241 C

5.4.2 Brake cable Removal and installation

– Unhook brake spring, b 5.4

support (2) with a gentle twisting motion

: Push hook (1) through the

– Remove QuickStop Super

throttle trigger, b 11. 3

– Remove QuickStop Super trigger

switch, b 11.3.1

: Pull brake cable (1) out slightly

and disconnect it

– Loosen tank housing and lower it,

b 13.11.2

– Do not overextend fuel hose

: Examine brake cable (1) and

support (2), replace if necessary

Dismantle brake cable and support

2410RA040 TG

3 4

: Unscrew clamping screw (1) and

adjusting screw (2)

2310RA053 TG

2310RA056 TG

: Turn adjusting screw (1) until the

distance between the hexagon of the adjusting screw and the

holder is 2 mm

: Screw in the clamping screw (2)

and tighten

2310RA054 TG

: Remove screw (1)

: Remove support (2) with brake

cable

: Turn hook (3) so that the angled

part is at the opening (arrow) and twist it out of the support (4)

Installation

2410RA041 TG

: Turn hook (1) so that it runs along

the support (2) and push it into the hole (arrow)

2410RA042 TG

: Guide the brake cable (1) over

fuel hose (3) or, in versions with manual fuel pump, over the fuel hose (3) and fuel return line (2)

: Push brake cable (1) with short

hook (4) in front through the hole (arrow) in the crankcase

2310RA055 TG

27MS 241 C

reverse order

– Adjust brake cable and check

– Reassemble remaining parts in

operation, b 5.4.1

5.5 Cam lever

: Push brake cable (1) with sleeve

into the hole in the housing (arrow) as far as it will go

1 2

: Hook brake cable (1) into

hole (arrow) in brake lever (2)

2410RA043 TG

When raising the tank housing, make certain that the sleeve (1) is pushed completely into the adjusting screw (2) – incomplete insertion of the sleeve changes the setting of the brake cable.

– Check position of the fuel hose

and correct it if necessary, b 13.11.2

– Check position of the fuel return

line and correct it if necessary, b 13.11.3

2410RA044 TG

– Raise and fasten the

tank housing, b 13.11.2

2410RA046 TG

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

– Remove brake lever, b 5.3,

QuickStop Super, b 5.4

: Unhook the brake spring (1) from

the anchor pin (2)

– Unhook and remove the brake

spring (1) at the cam lever

2410RA048 TG

: Press brake cable holder with the

pin (1) through the opening and into the mount (arrow)

: Screw in the screw (2) and

tighten it

2410RA045 TG

: Insert brake cable (1) in

guide (arrow)

– Install QuickStop Super trigger

switch, b 11.3.1

– Install QuickStop Super throttle

trigger, b 11.3

: Push out circlip (3)

– Remove cam lever

2410RA047 TG

28 MS 241 C

5.6 Pins

The pins ensure that the springs are securely mounted. They must

therefore be replaced when worn, otherwise the springs may pop out.

: Examine cam lever (1) and brake

spring (2) and replace if necessary

: Check condition of cam

guide (arrow) and replace hand guard if necessary

– Examine all pins and replace if

necessary, b 5.6

Installation

– Clean pins and disassembled

parts, b 16

– Grease pins, b 16

2410RA049 TG

: Push circlip (1) into place

: Hook brake spring (1) into the

brake lever so that the opening of the anchor loop (arrow) is visible

: Hook brake spring (1) onto

pin (2)

The pins must be driven in square.

For reasons of simplicity, the parts

2410RA051 TG

connected to the pins have already been removed in the following illustrations.

132

2410RA052 TG

: Remove pins (1) through (6)

Item 6 is present only in the version with QuickStop Super.

2410RA053 TG

: Orient cam lever (1) so that the

cam (arrow) faces the pin (3)

: Slide cam lever (1) onto anchor

pin (2)

– Grease cam lever, b 16

The cam lever is not yet tensioned – the spring may become detached again.

– Reassemble remaining parts in

reverse order

2410RA050 TG

29MS 241 C

+ 144 hidden pages