Ignition System - Stihl MS 440 Service Manual

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
Engine runs roughly, misfires,
temporary loss of power
10
Cause
Spark plug boot is loose
Spark plug sooted, smeared
with oil
Incorrect air gap between ignition
module and flywheel
Flywheel cracked or has other
damage or pole shoes have turned
blue
Ignition timing wrong, flywheel out
of adjustment, key in flywheel has
sheared off
Weak magnetization in flywheel –
pole shoes have turned blue
No spark
No spark
Leak in crankcase
Remedy
Press boot firmly onto spark plug
and fit new spring if necessary
Clean the spark plug or replace if
necessary
Set air gap correctly
Install new flywheel
Install new flywheel
Install new flywheel
Check operation of Master Control
lever and ignition module
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
Replace oil seals or crankcase
MS 440, MS 440 C