Stihl MS 461 Rescue User manual

STIH)
STIHL MS 461 2013-10

1MS 461, MS 461-R
q
© ANDREAS STIHL AG & Co. KG, 2013
RA_773_00_01_02
1. Introduction and
Safety Precautions 3
1.1 Introduction 3
1.2 Safety Precautions 4
2. Specifications 5
2.1 Motor 5
2.2 Fuel System 5
2.3 Ignition System 5
2.4 Chain Lubrication 5
2.5 Tightening Torquese 6
3. Troubleshooting 8
3.1 Clutch 8
3.2 Chain Drive, Chain
Brake, Chain
Tensioner 9
3.3 Chain Lubrication 10
3.4 Rewind Starter 11
3.5 Ignition System 12
3.6 Carburetor 13
3.7 Engine 16
4. Clutch 17
4.1 Clutch Drum 17
4.2 Clutch 17
5. Chain Brake 19
5.1 Checking Operation 19
5.2 Brake Band 19
5.3 Brake Lever 20
5.4 Cam Lever 22
5.5 Pins 22
5.6 Chain Tensioner 23
5.7 Bar Mounting Studs 24
6. Engine 25
6.1 Muffler 25
6.2 Leakage Test 26
6.2.1 Preparations 26
6.2.2 Vacuum Test 27
6.2.3 Pressure Test 28
6.3 Oil Seals 28
6.4 Shroud 30
6.5 Cylinder 30
6.6 Crankshaft 33
6.6.1 Bearings / Crankcase 37
6.7 Piston 38
6.8 Piston Rings 39
6.9 Decompression Valve 40
7. Ignition System 41
7.1 Ignition Timing 41
7.2 Install new
ignition module 41
7.3 Testing the
Ignition Module 43
7.3.1 Testing Ignition Module
with MDG 1 Engine
Analyzer 43
7.4 Spark Plug Boot /
Ignition Lead 44
7.5 Flywheel 45
7.6 Wiring Harness 46
7.6.1 Testing 46
7.6.2 Ground Wire 46
7.6.3 Wiring Harness
Removing and
Installing 47
7.6.4 Wiring Harness
Removing and
Installing on Models
with Heating System 49
7.6.5 Contact Spring 53
7.7 Ignition System
Troubleshooting 54
8. Rewind Starter 57
8.1 General 57
8.2 Rewind Starter
Removing
and Installing 57
8.3 Pawls 57
8.4 Rope Rotor 58
8.5 Starter Rope / Grip 58
8.6 Tensioning
the Rewind Spring 59
8.7 Replacing
the Rewind Spring 60
9. AV Elements 61
9.1 Annular Buffer on
Fuel Tank /
Clutch Side 61
9.1.1 Annular Buffer on
Fuel Tank /
Ignition Side 61
9.1.2 Annular Buffer on
Spiked Bumper /
Clutch Side 62
9.1.3 Annular Buffer on
Oil Tank /
Ignition Side 63
9.1.4 Stop Buffer at
Clutch Side 64
9.1.5 Stop Buffer at
Ignition Side 64
9.2 Handlebar 64
9.2.1 Wrap Around
Handlebar on
Rescue Saw 65
9.2.2 Handlebar
with Heating 66
10. Control Levers 69
10.1 Master Control Lever 69
10.1.1 Removing and
Installing 69
10.2 Throttle Trigger /
Lockout Lever 70
10.3 Throttle Rod 71
10.3.1 Throttle Rod on
Models with Heating 72
11. Chain Lubrication 73
11.1 Pickup Body 73
11.2 Oil Suction Hose 73
11.3 Oil Pump 73
11.3.1 Adjusting Uprated
Oil Pumps 74
11.4 Valve 75
12. Fuel System 76
12.1 Air Filter 76
12.2 Baffle 76
12.3 Filter Base 76
12.4 Carburetor 77
12.4.1 Leakage Test 79
12.5 Servicing
the Carburetor 79
12.5.1 Metering Diaphragm 79
12.5.2 Inlet Needle 80
12.5.3 Pump Diaphragm 81
12.5.4 Adjusting Screws 82
12.6 Adjusting
the Carburetor 84
12.6.1 Basic Setting 84
12.6.2 Setting 85
12.6.3 Standard Setting 86
12.7 Intake Manifold 87
Contents

2MS 461, MS 461-R
Contents
12.7.1 Impulse Hose 88
12.8 Tank Vent 88
12.8.1 Testing 88
12.8.2 Removing and
Installing 89
12.9 Fuel Intake 89
12.9.1 Pickup Body 89
12.9.2 Fuel Hose 90
12.9.3 Tank Housing 91
13. Heating System 93
13.1 Carburetor Heating 93
13.1.1 Testing the Complete
System 93
13.1.2 Testing the Heating
Element 93
13.1.3 Thermostatic Switch 94
13.2 Carburetor Heating
System
Troubleshooting Chart 95
13.3 Handle Heating
System 96
13.3.1 Troubleshooting 96
13.4 Heater Switch 96
13.5 Heating Element
in Rear Handle 98
13.6 Heating Element
in Handlebar 99
13.7 Generator 100
13.8 Wiring Harness 101
13.8.1 Handle Heating
and Generator
Troubleshooting
Chart 102
13.8.2 Test Connections
and Test Values 104
14. Special Servicing
Tools 106
15. Servicing Aids 108

3MS 461, MS 461-R
1. Introduction and Safety Precautions
1.1 Introduction
This service manual contains
detailed descriptions of all the repair
and servicing procedures specific to
this power tool.
You should make use of the
illustrated parts lists while carrying
out repair work. They show the
installed positions of the individual
components and assemblies.
Refer to the latest edition of the
relevant parts list to check the part
numbers of any replacement parts.
A fault on the machine may have
several causes. To help locate the
fault, consult the chapter on
"Troubleshooting" and the
"STIHL Service Training System"
for all assemblies.
Refer to the “Technical Information”
bulletins for engineering changes
which have been introduced since
publication of this service manual.
Technical information bulletins also
supplement the parts list until a
revised edition is issued.
The special tools mentioned in the
descriptions are listed in the chapter
on "Special Servicing Tools" in this
manual. Use the part numbers to
identify the tools in the
"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 that is
shown in the illustration
(above the text)
– = Action to be taken that is
not shown in the illustration
(above the text)
In the illustrations:
APointer (short arrow)
aDirection of movement
b4.2 = 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.
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 above operation is not
necessary with the new assembly
stand 5910 890 3101 since the
mounting plate is already fitted.
1
2
3
219RA000 TG
The screws must not project since
they, depending on the machine,
may damage housings when the
machine is clamped in position.
Preparations for servicing
The chain sprocket, saw chain and
guide bar must be removed to
mount the machine on the assembly
stand for servicing.
Engage the bar mounting studs in
the lower holes in the mounting
plate and secure the machine in
position with the M 8 nuts (arrows).
3443RA000 TG

4MS 461, MS 461-R
Always use original STIHL
replacement parts.
They can be identified by the STIHL
part number,
the STIH) logo and the
STIHL parts symbol (
This symbol may appear alone on
small parts.
Storing and disposing of fuels
Collect fuel in a clean container and
dispose of it properly in accordance
with local environmental
regulations.
Connectors in electrical wires
The insulating tube must be
centered on the connector and
completely cover it
– there is otherwise a risk of a short
circuit.
The connector is properly
assembled when its overall length is
a = no more than 30 mm.
Positioning wires
Always use punch down tool
5910 890 4000 to press electrical
wires fully into their guides.
5902RA299 TG
a
1.2 Safety Precautions
If the machine is started up in the
course of repairs or maintenance
work, observe all local and country-
specific safety regulations as well
as the safety precautions and
warnings in the instruction manual.
Fuel is extremely flammable and
can be explosive in certain
conditions.
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.
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.
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.
Always replace damaged parts.
Check disassembled parts for wear
or damage before re-installing –
replace as necessary.
Run the machine only with the
rewind starter and shroud mounted
in position – there is otherwise a risk
of injury from the flywheel and a risk
of engine damage due to
overheating.
Remove the spiked bumper
to reduce the risk of injury from
contact with the sharp tips.
The chapter on tightening torques
lists all machine components that
have to be tightened to a specific
torque or coated with threadlocking
adhesive. The specifications must
be maintained when tightening
down screws, nuts and other
fasteners in all the procedures
described in this service manual.
Fuel system – hose barb
connectors
Pull off or push on fuel hoses in line
with the connector, preferably by
hand, to ensure the tightness of the
fuel system.
Avoid damaging the hose barb
– do not use sharp-edged pliers,
screwdrivers, etc.
Do not cut open fuel hoses with a
knife or similar tool.
Do not re-use fuel hoses after
removal. Always install new hoses
– fuel hoses can be overstretched
during removal.
Install new fuel hoses either dry or
with the aid of STIHL press fluid
– coat the ends of hoses and the
connectors, b15.
Other press fluids are not approved
and may result in damage to the fuel
hoses.

5MS 461, MS 461-R
2. Specifications
2.1 Motor
MS 461, MS 461-R
Displacement: 76.5 cm3
Bore: 52.0 mm
Stroke: 36.0 mm
Engine power to ISO 7293: 4.4 kW (6.0 HP)
at 9,800 rpm
Max. speed (with cutting attachment): 1) 13,500 rpm 1)
Idle speed: 2,500 rpm
Clutch: Centrifugal, without linings
Clutch engages at: 3,500 rpm
Crankcase leakage test
at gauge pressure: 0.5 bar
under vacuum: 0.5 bar
2.2 Fuel System
Carburetor leakage test at
gauge pressure: 0.8 bar
Operation of tank vent at
gauge pressure: 0.5 bar
Fuel: see instruction manual
2.3 Ignition System
Air gap between ignition
module and fanwheel: 0.20 (+ 0.1/- 0.05) mm
Spark plug (resistor type): BOSCH WSR 6 F
NGK BPMR 7 A
Electrode gap: 0.5 mm
2.4 Chain Lubrication
Speed-controlled oil pump with reciprocating piston and
manual flow control
Standard / Uprated
Standard
Uprated
Settings for oil delivery rate:
min.:
max.:
max.:
6.0 (+/- 2.0) cm3/min
at 10,000 rpm
17.0 (+/- 3.0) cm3/min
at 10,000 rpm
24.0 (+/- 3.0) cm3/min
at 10,000 rpm
1) The engine reaches its maximum RPM and maximum power after the break-in period (5 to 10 tank fillings) –
do not make any changes to the high speed screw (H) during the break-in period.

6MS 461, MS 461-R
2.5 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.
Use the following procedure when refitting a DG or P screw in an existing thread:
Insert the screw in the hole and rotate it counterclockwise until it drops down slightly and engages in the existing
thread. 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.
Before reinstalling a micro-encapsulated screw, clean both threads (screw tap into female thread by hand and
then blow out with compressed air, clean male thread with brush), coat clean screw with medium strength
Loctite 242 or 243.
Power screwdriver setting for polymer: P and DG 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.
Fastener Thread size For component Torque
Nm
Remarks
Screw M 4x8 Chain tensioner cover plate/crankcase 3.0
Screw M 4x12 Brake band/crankcase 3.0 4), 5)
Collar screw M 8x21.5 Collar stud / crankcase, for bar 23.0 2)
Screw M 4x12 Cover, chain brake/crankcase 3.0 4), 6)
Screw M 4x12 Cover, oil pump/crankcase 3.0 4), 6)
M 10x1 Decompression valve 14.0
Collar nut M 5 Filter cover / twist lock 1.0
Collar nut M 5 Flange / filter base / carburetor 3.5
Screw M 4x10 Flange / crankcase 2.5 5)
Screw M 4x12 Generator / crankcase 3.0 4), 5), VW
Screw P 6x21.5 Handlebar, top / tank housing 8.0 3)
Screw P 6x32.5 Handlebar, top / tank housing 8.0 3), R
Screw P 6x19 Handlebar, bottom / tank housing 8.0 3)
Screw P 4x19 Handle Molding 1.6
Screw M 5x35x22 Hand guard, left 7.0 4), 6)
Screw M 5x23 Shroud / crankcase 6.0
Nut M 5 Shroud / cylinder 3.5
Locknut M 5 Chain catcher / spiked bumper 6.0 R
Screw M 5x20 Chain catcher / spiked bumper / crankcase,
bottom
8.0 5)

7MS 461, MS 461-R
Fastener Thread size For component Torque
Nm
Remarks
Screw M 5x20 Chain catcher / guard plate / crankcase,
bottom
8.0 5), R
Locknut M 5 Spiked bumper / chain sprocket cover / screw 6.0
Screw M 5x12 Spiked bumper / crankcase, top / locknut 8.0 4), 6)
Screw M 5x12 Crankcase / guard plate / locknut 8.0 4), 6), R
Screw M 5x25 Crankcase, sprocket side / fan side 10.0 4), 6)
Screw M 5x20 Fan housing 7.0 4), 6)
Carrier M 12x1 L Carrier 50.0
Screw M 4x12 Oil pump / crankcase 3.5 4), 6)
Screw M 4x16 Annular buffer / crankcase 4.5 1), 5)
Screw P 6x19 Annular buffer / tank housing, rear 5.5
Screw P 6x32.5 Annular buffer / tank housing, rear / ignition
side, top
5.5
Screw P 6x19 Annular buffer / tank housing, front 5.5
Screw M 5x20 Wrap-around handle with bracket 7.0 4), 6)
Screw M 6x30 Muffler / crankcase 15 1), 4), 6)
Screw M 5x16 Muffler / cylinder 11.5 1), 4)
Screw M 5x6 Muffler, top 6.5 4), 5)
Screw M 6x30 Muffler, ign. side / crankcase 15 1), R
Screw B 2.9x9.5 Switch housing 1.0
Screw B 3.9x13 Guard / tank housing 2.8
Screw M 5x10 Guard plate / screw, muffler 7.5 4), 5), R
Nut M 8x1 Flywheel / crankshaft 33.0 7)
Screw M 4x8 Side plate / crankcase 3.0
Screw M 3x20 Clamp / manifold 0.5
Nut M 12x075 Tank housing / switch 2.0 VW
M 14x1.25 Spark plug 25.0
Screw M 5x20 Ignition module / crankcase 7.0 4), 5)
Screw M 6x30 Cylinder / crankcase 15.0 4), 6)
Remarks:
1) Loctite 242 or 243, medium strength
2) Loctite 270, high strength
3) Loctite 649, high strength
4) Screws with binding head
5) Micro-encapsulated screws
6) Waxed screws
7) Degrease crankshaft/flywheel and mount oil-free
VW) Carburetor and handle heating system
R) Rescue saw

8MS 461, MS 461-R
3. Troubleshooting
3.1 Clutch
Condition Cause Remedy
Saw chain stops under full load Clutch shoes badly worn Install new clutch
Clutch drum badly worn Install new clutch drum
Saw chain runs while engine is
idling
Engine idle speed too high Readjust idle speed screw LA
Clutch springs stretched Replace the clutch springs or install
new clutch
Clutch springs broken Replace the clutch springs
Loud noises Clutch springs stretched Replace all clutch springs
Needle cage damaged Fit new needle cage
Clutch shoe retainer broken Install new retainer or clutch
Clutch shoes and carrier worn Install new clutch

9MS 461, MS 461-R
3.2 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
Saw chain stops under full load 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
Saw chain runs while engine is
idling
Engine idle speed too high Readjust idle speed screw LA
Clutch springs stretched Replace the clutch springs or install
new clutch
Clutch springs broken Replace the clutch springs
Saw chain does not stop
immediately when brake is
activated
Chain brake spring
stretched / broken
Fit new brake spring
Brake band
stretched / worn / broken
Fit new brake band
Clutch drum worn Install new clutch drum

10 MS 461, MS 461-R
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.
.
Condition Cause Remedy
Chain receives no oil Oil inlet hole in guide bar is blocked Clean oil inlet hole
Intake hose or pickup body clogged
or intake hose ruptured
Fit new intake hose and pickup
body
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 damaged or worn Install new oil pump
Oil suction hose connection
damaged
Install new oil suction hose
Gasket between two halves of
crankcase faulty or crankcase
cracked
Install new gasket, inspect both
halves of crankcase and replace if
necessary
Oil pump delivers insufficient oil Oil pump damaged or worn Install new oil pump
Oil pump delivery rate set too low Adjust oil pump
(only on machines with adjustable
oil pump)
Worm driver is loose Install new worm
Sealing ring between oil pump and
crankcase damaged
Replace the sealing ring

11MS 461, MS 461-R
3.4 Rewind Starter
Condition Cause Remedy
Starter rope broken Rope pulled out too vigorously as
far as stop or over edge, i.e. not
vertically
Install new starter rope
Normal wear Install new starter rope
Starter rope does not rewind Rewind spring very dirty or
corroded
Clean or replace rewind spring
Insufficient spring tension Check rewind spring and increase
tension
Rewind spring broken Install new rewind spring
Starter rope cannot be pulled out
far enough
Spring overtensioned Check rewind spring and reduce
tension
Starter rope can be pulled out
almost without resistance
(crankshaft does not turn)
Guide pegs on pawls or pawls
themselves are worn
Replace pawls
Spring clip on pawl fatigued Fit new spring clip
Spring clip not installed properly Install spring clip correctly
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:
Lubricating oil on rewind spring
becomes viscous (spring windings
stick together) or moisture has got
onto the rewind spring (spring
windings frozen together)
Coat rewind spring with a small
amount of standard solvent-based
degreasant (containing no
chlorinated or halogenated
hydrocarbons), then pull rope
carefully several times until normal
action is restored

12 MS 461, MS 461-R
3.5 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, fit
new spring/spark plug boot 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
Install new ignition lead
Fuel/oil mixture
– too much oil
Use correct mixture of fuel and oil
Incorrect air gap between ignition
module and flywheel
Set air gap correctly
Flywheel cracked or
damaged or pole shoes have
turned blue
Install new flywheel
Ignition timing wrong, flywheel out
of adjustment
– key has sheared off or slot in
flywheel is worn
Install new flywheel or key
Weak magnetization in flywheel Install new flywheel
Irregular spark Check operation of switch shaft/
contact spring and ignition module
Faulty insulation or break in ignition
lead or short circuit wire. Check
ignition lead/ignition module and
replace as necessary.
Check operation of spark plug.
Clean the spark plug or replace if
necessary.
The carburetor or engine may also be the cause of poor engine running behavior

13MS 461, MS 461-R
3.6 Carburetor
Condition Cause Remedy
Carburetor floods; engine stalls Inlet needle not sealing
– foreign matter in valve seat or
cone
Remove and clean the inlet needle,
clean the carburetor
Inlet needle worn Fit new inlet needle
Inlet control lever sticking on
spindle
Check the inlet control lever and
replace if necessary
Helical spring not located on nipple
of inlet control lever
Remove the inlet control lever and
refit it correctly
Perforated disc on diaphragm is
deformed and presses constantly
against the inlet control lever
Fit new metering diaphragm
Metered diaphragm deformed Fit new metering diaphragm
Poor acceleration Setting of low speed screw too lean Check basic carburetor setting,
correct if necessary
Setting of high speed screw too
lean
Check basic carburetor setting,
correct if necessary
Inlet needle sticking to valve seat Remove inlet needle, clean and
refit
Metering diaphragm or gasket
damaged
Fit a new metering diaphragm and
gasket
Tank vent faulty Fit new tank vent
Leak in fuel hose between pickup
body and carburetor
Seal connections or install new fuel
hose

14 MS 461, MS 461-R
Condition Cause Remedy
Engine will not idle, idle speed too
high
Throttle shutter opened too wide by
idle speed screw (LA)
Reset idle speed screw (LA)
correctly
Oil seals/crankcase leaking Seal oil seals / crankcase, replace if
necessary
Throttle shutter does not close Install new carburetor
Engine stops while idling Idle jet bores
or ports blocked
Clean the carburetor
Low speed screw too rich or
too lean
Reset low speed screw (L)
correctly
Setting of idle speed screw LA
incorrect – throttle shutter
completely closed
Reset idle speed screw (LA)
correctly
Tank vent faulty Fit new tank vent
Leak in fuel hose between pickup
body and carburetor
Seal connections or install new fuel
hose
Saw chain runs while engine is
idling
Engine idle speed too high Readjust with idle speed screw
LA (counterclockwise)
Clutch springs stretched or fatigued Replace the clutch springs or install
new clutch
Clutch spring hooks broken Replace the clutch springs

15MS 461, MS 461-R
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 Fit new tank vent
Fuel pickup body dirty Fit new pickup body
Fuel strainer dirty Clean fuel strainer in carburetor,
replace if necessary
Leak in fuel hose between pickup
body and carburetor
Seal connections or install new fuel
hose
Setting of high speed screw (H) too
rich
Check basic carburetor setting,
correct if necessary
Main jet bores or ports blocked Clean the carburetor
Pump diaphragm damaged or
fatigued
Fit new pump diaphragm
Ignition timing wrong, flywheel out
of adjustment
– key has sheared off or slot in
flywheel is worn
Install new flywheel or key
Engine running extremely rich, has
no power and a very low maximum
speed
Choke shutter does not open fully Check carburetor and choke shaft,
service or replace if necessary

16 MS 461, MS 461-R
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
Condition Cause Remedy
Engine does not start easily, stalls
at idle speed, but operates normally
at full throttle
Oil seals in crankcase damaged Replace the oil seals
Crankcase leaking or damaged
(cracks)
Seal or replace the crankcase
Engine does not deliver full power
or runs erratically
Piston rings worn or broken Install new piston rings
Muffler / spark arresting screen
carbonized
Clean the muffler (inlet and
exhaust), replace spark arresting
screen, replace muffler if necessary
Air filter dirty Clean or replace air filter
Fuel hose kinked or torn Fit new hose or position it free from
kinks
Decompression valve is not closed Close and check decompression
valve, replace if necessary
Engine overheating Insufficient cylinder cooling. Air
inlets in fan housing blocked or
cooling fins on cylinder very dirty
Thoroughly clean all cooling air
openings and the cylinder fins
Air inlet in fan housing dirty Clean air inlet on fan housing

17MS 461, MS 461-R
4. Clutch
4.1 Clutch Drum
– Remove and install the clutch
drum, see instruction manual.
:Pull off the needle cage (1).
– Clean the needle cage and
crankshaft stub, b15
– Lubricate needle cage and
crankshaft stub with STIHL
grease, b15
– Inspect the clutch drum (1) for
signs of wear.
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.
– Install the clutch drum.
3443RA047 TG
1
!
80%
100%
5902RA018 TG
1
4.2 Clutch
– Troubleshooting, b3
– Remove the filter cover
– Remove air baffle.
– Pull off the boot and unscrew the
spark plug.
:Push the locking strip (1)
0000 893 5903 into the spark
plug hole, wide end first, so that
"OBEN-TOP" faces up.
:The locking strip (1)
0000 893 5903 must butt against
the cylinder wall (arrow)
– as shown in the illustration.
– Remove the rim sprocket and
clutch drum.
3443RA004 TG
1
3443RA493 TG
1
:Apply wrench to hexagon (arrow)
and unscrew the clutch (1).
Note that the clutch has a left-hand
thread.
Disassembling
:Use hook (2) 5910 890 2800 to
remove the clutch springs (1).
If clutch is seriously worn, install
new set of 3 clutch shoes.
Assembling
:Fit the retainers (1) and push the
clutch shoes (2) over the
arms (3) of the carrier.
3443RA048 TG
1
off
off
off
5902RA006 TG
21
off
3443RA464 TG
31
2

18 MS 461, MS 461-R
Attach the springs at the side with
the raised hexagon (arrow).
– Clamp the clutch in a vise – one
clutch shoe horizontal as shown.
: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.
– Check the clutch – all springs
must be properly attached.
The washer (1) must be in place
and the word "TOP" (arrow) must
face outwards.
off
off
5902RA012 TG
1
2
TOP
1
3443RA049 TG
:Position the clutch (1) on the
crankshaft stub so that the raised
hexagon (arrow) faces outwards.
:Fit the clutch (1) and tighten it
down firmly – left-hand thread.
– Remove the locking strip from the
cylinder.
– Install the rim sprocket and clutch
drum.
– Fit the spark plug and tighten it
down firmly.
– Fit the boot on the spark plug.
– Fit the air baffle.
– Fit the filter cover.
TOP
1
3443RA050 TG

19MS 461, MS 461-R
5. Chain Brake
5.1 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.
– 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 is
imperceptible to the eye (a fraction
of a second).
If the chain brake does not operate
properly, refer to troubleshooting,
b3.2.
5.2 Brake Band
– Troubleshooting, b3.2
– Remove the clutch drum,
:Take out the screw (1) and
remove the side plate (2).
:Take out the screws (1).
:Remove covers (2) and (3).
2
3443RA051 TG
1
3443RA052 TG
21
1
1
3
– Engage the chain brake
– Brake band no longer
tensioned in its seat.
:Take out the screw (1).
:Ease the brake band (2) out of its
seat (arrow) and lift it away.
Do not overstretch the brake band.
– Disengage the chain brake.
– the brake band can be
disconnected when the brake
lever is in this position.
:Turn the brake band (1) to one
side and disconnect it from the
brake lever (2).
3443RA023 TG
2
1
3443RA024 TG
1
2