13FS 240 C, FS 260 C, FS 360 C, FS 410 C, FS 460 C-M
3.5 Ignition system
Problem 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
In the event of repeated sooting, 
check air filter
Fuel/oil mixture 
– contains too much oil
Use a fuel mixture with the correct 
mixing ratio
Incorrect air gap between ignition 
module/control unit and flywheel
Set the correct air gap
Flywheel cracked
or has other damage or pole shoes 
have turned blue
Install new flywheel
Incorrect ignition timing, flywheel 
out of adjustment 
– Key in flywheel has sheared off
Install new flywheel
Weak magnetization in flywheel Install new flywheel
Irregular spark Check proper functioning of lever 
for stop function/contact spring or 
slide control/microswitch and 
ignition module.
Damaged insulation or interruption 
in ignition lead or short circuit wire. 
Check ignition lead/ignition module, 
replace ignition module if 
necessary. Check operation of 
spark plug, clean spark plug and 
replace if necessary.
Versions with M-Tronic, carry out 
diagnosis