Stihl MS 240, MS 260 Instruction Manual
STIH)
STIHL MS 240, 260
2013-09
Contents
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
q
© ANDREAS STIHL AG & Co. KG, 2013
1MS 240, MS 260, MS 260 C
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
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
1
3
2
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
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
1
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
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
3. Specifications
3.1 Engine
MS 240 MS 260, MS 260 C
Displacement: 41.6 cm
3
50.2 cm
3
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
3
/min at
3
/min at
6 MS 240, MS 260, MS 260 C
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
Nm
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
4)
7MS 240, MS 260, MS 260 C
Fastener Thread size For component Torque
Nm
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
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
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
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
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
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
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
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
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
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
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
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
5. Cutting Attachment
3
2
1
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.
1
165RA002 TG
: Carefully pry the wing nut (1) out
of the sprocket cover (arrow).
– Check the wing nut (1) and
replace if necessary
1
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
1
165RA247 TG
Versions with Quick Chain
Tensioner
4
3
2
1
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
1
2
: 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
6. Clutch
– Troubleshooting, b 4.1
– Remove the sprocket cover and
cutting attachment, b 5
– Remove the clutch drum, b 6.1
1
– Remove the air filter, b 14.1
– Remove the shroud, b 8.4
: Pull boot (1) off the spark plug.
1
: Push the locking strip (1)
0000 893 5903 into the cylinder
so that "OBEN-TOP" is visible.
1
165RA009 TG
1
165RA011 TG
– Pull the clutch shoes off the
carrier.
: Remove the retainers (1).
165RA014 TG
1
: Unscrew the spark plug (1).
: Unscrew the clutch (1).
Note that the clutch has a left-hand
thread.
2
1
165RA010 TG
Disassembling
: Use hook (2) 5910 890 2800 to
remove the clutch springs (1).
165RA012 TG
– Clean all parts..
– Replace any damaged parts.
1
165RA013 TG
: Fit the retainers (1).
165RA015 TG
165RA016 TG
20 MS 240, MS 260, MS 260 C
21
1
: Fit the clutch shoes (2) over the
arms (2).
: Clamp the clutch in a vise
(arrow).
2
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.
1
– Reassemble all other parts in the
reverse sequence.
165RA021 TG
165RA023 TG
1
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
6.1 Clutch Drum
1
1
– Remove the sprocket cover and
cutting attachment, b 5
: Pull the hand guard (1) towards
the handlebar.
1
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
2
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.
1
165RA029 TG
1
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
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
1
: 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).
2
1
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.
1
– 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.
1
165RA038 TG
165RA039 TG
: Remove the cover (1).
23MS 240, MS 260, MS 260 C
1
1
: Pry the brake band (1) out of its
seat (arrow).
– Remove the brake band (1).
Do not over-stretch the brake band.
1
: Turn the brake band (1) to one
side and disconnect it from the
brake lever (arrow).
165RA040 TG
1
: Hold the brake band (1)
sideways, attach it to the brake
lever (arrow) and then swing it in
the direction of its seat.
1
: 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.
1
: 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.
1
– 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.
7.3 Brake Lever
1
1
– 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
1
: 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
2
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).
2
1
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
1
2
: Lift the bearing boss of the hand
guard and the brake lever a little
and position them over the pivot
pins (arrows).
1
: 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
1
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
1
1
: 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
1
1
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.
2
1
– 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).
2
: 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).
1
: Use a suitable tool to pull out the
165RA065 TG
pins (arrows).
1
165RA066 TG
1
2
– 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
2
4
a
7.6 Side Chain Tensioner
– Remove the sprocket cover and
3
cutting attachment, b 5
5
c
– Troubleshooting, b 4.2
1
: Drive home the pins (1 and 2) as
shown in the illustrations.
a
1
2
b
: 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
b
165RA378 TG
2
1
– 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
3
4
: Drive home pins (3, 4 and 5) as
specified below.
28 MS 240, MS 260, MS 260 C
5
: Take out the screw (arrow).
– Pull out the tensioner side with
adjusting screw, thrust pad and
spur gear.
165RA460 TG
7.6.1 Front Chain Tensioner
3
– Remove the sprocket cover and
2
6
1
4
cutting attachment, b 5
– Troubleshooting, b 4.2
2
1
5
– 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
2
: 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).
3
: Pull off the thrust pad (1) and
unscrew the adjusting screw (2)
from the tensioner slide (3).
– Check the individual parts and
1
3
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
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