Ignition System - Stihl MS 661 Manual

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
Engine runs roughly,
misfires, temporary loss of
power
The carburetor or engine may also be the cause of poor engine running behavior
12
Cause
Spark plug boot is loose
Spark plug sooted, smeared with oil Clean the spark plug or replace if
Ignition lead loose in ignition
module
Fuel/oil mixture
– too much oil
Incorrect air gap between ignition
module / control unit and flywheel
Flywheel cracked or
damaged or pole shoes have
turned blue
Ignition timing wrong, flywheel out
of adjustment
– key has sheared off or slot in
flywheel is worn
Weak magnetization in flywheel
Irregular spark
Remedy
Press boot firmly onto spark plug, fit new
spring and spark plug boot if necessary
necessary.
If sooting keeps recurring, check air filter
Install new ignition lead
Use correct mixture of fuel and oil
Set air gap correctly
Install new flywheel
Install new flywheel or key
Install new flywheel
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.
MS 661, MS 661 C-M