Stihl MS 661 C-M User Manual

1MS 661, MS 661 C-M
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© ANDREAS STIHL AG & Co. KG, 2013
RA_758_00_01_01
1. Introduction and
Safety Precautions 3
1.1 Introduction 3
1.2 Safety Precautions 4
2. Specifications 5
2.1 Engine 5
2.2 Fuel System 5
2.3 Ignition System 5
2.4 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 17
4. Clutch 18
4.1 Clutch Drum 18
4.2 Clutch 18
5. Chain Brake 19
5.1 Checking Operation 19
5.2 Brake Band 19
5.3 Brake Lever 20
5.4 Cam Lever 21
5.5 Pins 21
5.6 Chain Tensioner 22
5.7 Bar Mounting Studs 23
5.8 Collar Nuts for
Sprocket Cover 23
6. Engine 24
6.1 Muffler 24
6.2 Leakage Test 25
6.2.1 Preparations 25
6.2.2 Vacuum Test 26
6.2.3 Pressure Test 26
6.3 Oil Seals 26
6.3.1 Ignition Side 26
6.3.2 Clutch Side 27
6.4 Shroud 28
6.5 Cylinder 28
6.6 Crankshaft 31
6.6.1 Bearings / Crankcase 35
6.7 Piston 36
6.8 Piston Rings 38
6.9 Decompression Valve 38
7. Ignition System 39
7.1 Ignition Timing
on All Models 39
7.2 Ignition Module /
Control Unit 39
7.3 Removing and
Installing 39
7.4 Testing the
Ignition Module 41
7.4.1 Testing Ignition Module
with MDG 1 Engine
Analyzer 41
7.5 Spark Test 42
7.6 Spark Plug Boot /
Ignition Lead 43
7.7 Flywheel 44
7.8 Testing Wiring
Harness 45
7.8.1 Testing Wiring Harness
without M-Tronic 45
7.8.2 Testing Wiring Harness
with M-Tronic 46
7.8.3 Testing Ground Wire 46
7.9 Short Circuit Wire /
without M-Tronic
Removing and
Installing 46
7.10 Short Circuit Wire /
with M-Tronic
Removing and
Installing 48
7.11 Short Circuit Wire /
with M-Tronic and
Heating
Removing and
Installing 50
7.12 Contact Spring 54
7.13 Ignition System
Troubleshooting 57
8. M-Tronic 60
8.1 Calibrating the
Control Unit 60
8.2 Testing with
STIHL MDG 1 61
8.3 Testing 61
8.3.1 Preparations 61
8.3.2 Connecting
Test Cables 62
8.3.3 Testing Screw and
Plug Connections and
Switch Contact 62
8.3.4 Checking the
Solenoid Valve 63
8.3.5 Checking Detection of
Start Conditions 64
8.3.6 Testing the Wiring
Harness 65
8.4 Wiring Harness 66
8.5 Switch Unit 66
8.6 Solenoid Valve 68
8.7 M-Tronic
Troubleshooting Chart 69
8.7.1 Circuit Diagram 69
8.7.2 Engine does not start 70
8.7.3 Engine does not start
in position } 71
8.7.4 Engine speed drops
under load – engine
down on power 72
8.7.5 Ignition – no spark 73
8.7.6 Engine stops
suddenly 74
8.7.7 Cut-off engine speed
is not reached 75
9. Rewind Starter 76
9.1 General 76
9.2 Rewind Starter
Removing and
Installing 76
9.3 Pawls 76
9.4 Rope Rotor 77
9.5 Starter Rope / Grip 77
9.6 Tensioning the
Rewind Spring 78
9.7 Replacing the
Rewind Spring 78
9.8 Segment 79
Contents

Stihl MS 661 C-M Specifications

General

Idle speed	- RPM
Motor type	2-stroke motor
Chain pitch	3/8 \
Blade length	800 mm
Product color	Black, Grey, Orange
Automatic oiling	Yes
Engine displacement	91.1 cm³
Power source	Gasoline
Sound power level	118 dB
Vibration emission	6.9 m/s²
Sound pressure level	105 dB

Weight and Dimensions

Weight	7400 g