Ignition System - Stihl 4180 Series Service Manual

3.3

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
Engine runs roughly, misfires, tem-
porary loss of power
Series 4180 Powerhead
Cause
Spark plug boot is loose
Spark plug sooted, smeared with oil
Wrong electrode gap
Incorrect air gap between ignition module
and flywheel
Flywheel cracked or has other damage,
pole shoes have turned blue
Ignition timing incorrect: Flywheel out of
adjustment, flywheel key sheared
Weak magnetization in flywheel pole
shoes
Intermittent or weak ignition spark
Remedy
Press boot firmly onto spark plug, check
leg spring, replace if necessary
Clean the spark plug or replace if
necessary
Check electrode gap, adjust if necessary
Set air gap correctly
Replace flywheel
Replace flywheel
Replace flywheel
Check operation of switch / contact springs
/ ignition module (with ZAT 3 or ZAT 4),
replace if necessary
Clean the spark plug or replace if
necessary
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