Checking The Spark Plug - Stihl FS 120 Instruction Manual

Cutting tool rotates when engine is
idling
: Turn idle speed screw (LA) slowly
counterclockwise until cutting tool
stops rotating and then turn the
1
screw about another /
the same direction.
Erratic idling behavior, engine stops
even though setting of LA screw is
correct, poor acceleration
Idle setting too lean:
: Turn low speed screw (L)
counterclockwise (about
until the engine runs and
accelerates smoothly.
Erratic idling behavior
Idle setting too rich:
: Turn low speed screw (L) clockwise
1
(about / turn) until the engine runs
4
and accelerates smoothly.
FS 120, FS 120 R, FS 200, FS 200 R, FS 250, FS 250 R

Checking the Spark Plug

to 1turn in
2
1
/ turn)
4
If engine is down on power, difficult to
start or runs poorly at idle speed, first
check the spark plug.
: Remove the spark plug –
see "Starting / Stopping the Engine".
: Clean dirty spark plug.
: Check electrode gap (A) and
readjust if necessary – see
"Specifications".
English / AUS
: Rectify the problems which have
caused fouling of spark plug:
– To much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions.
: Fit a new spark plug after
about 100 operating hours – or
sooner if the electrodes are badly
eroded.
Install only suppressed spark plugs
of the type approved by STIHL –
see "Specifications".
To reduce the risk of arcing
and fire:
: If the spark plug comes with a
detachable adapter nut (1), screw it
on firmly.
1
35