9Series 4144 Components FC, FS, KM
4.3 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 
and fit new spring if necessary
Spark plug sooted, smeared with oil Clean the spark plug or replace if 
necessary.
If sooting keeps recurring, check air 
filter
Fuel/oil mixture 
– too much oil
Use correct mixture of fuel and oil
Incorrect air gap between ignition 
module 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 on crankshaft 
has sheared off
Locate flywheel properly or install 
new flywheel
Weak magnetization in flywheel Install new flywheel
Irregular spark Check operation of switch shaft/
contact springs and ignition 
module.
Faulty insulation or break in ignition 
lead or short circuit wire. Check 
ignition lead/ignition module and 
replace ignition module if 
necessary.
Check operation of spark plug.
Clean the spark plug or replace if 
necessary.
Crankcase damaged (cracks) Install new crankcase