Stihl MS 390 User Manual

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

Stihl MS 390 Specifications

General

Brand	Stihl
Model	MS 390
Category	Chainsaw
Language	English