10 MS 290, MS 310, MS 390
4.4 Ignition System
Warning!
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 
and fit new spring if necessary
Spark plug sooted, smeared 
with oil
Clean the spark plug or replace if 
necessary
Incorrect air gap between ignition 
coil and flywheel
Set air gap correctly
Flywheel cracked or has other 
damage or pole shoes have turned 
blue
Install new flywheel
Ignition timing wrong, flywheel out 
of adjustment, key in flywheel has 
sheared off
Install new flywheel
Weak magnetization in flywheel – 
pole shoes have turned blue
Install new flywheel
No ignition spark Check operation of Master Control 
lever and ignition module
No ignition spark Faulty insulation on ignition lead or 
short circuit wire. Use ohmmeter to 
check ignition lead for break. If 
break is detected or high resistance 
measured, fit a new ignition lead 
Check operation of spark plug. 
Inspect Master Control lever, 
ignition coil/lead for damage 
insulation and leakage current.
Clean or replace spark plug, 
replace faulty parts of ignition 
system
Engine pan damaged (cracks) Replace engine pan