Stihl MS 661 C-M User Manual

12 MS 661, MS 661 C-M
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 and 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 / control unit 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 or control unit.
Damaged insulation or break in ignition lead
or short circuit wire – check ignition lead /
ignition module / control unit, replace if
necessary. Check operation of spark plug,
clean the spark plug, replace if necessary,
check M-Tronic with aid of troubleshooting
chart, b 8.7.
The carburetor or engine may also be the cause of poor engine running behavior

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