Stihl FS 250 R Product Instruction Manual - Page 41

Checking the Spark Plug - spark plug gap

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English / USA Checking the Spark Plug Cutting tool rotates when engine is idling : Turn idle speed screw (LA) slowly counterclockwise until cutting tool stops rotating and then turn the screw about another 1/2 to 1turn in 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 1/4 turn) until the engine runs and accelerates smoothly. Erratic idling behavior Idle setting too rich: : Turn low speed screw (L) clockwise (about 1/4 turn) until the engine runs and accelerates smoothly. Wrong fuel mix (too much engine oil in the gasoline), a dirty air filter and unfavorable running conditions (mostly at part throttle etc.) affect the condition of the spark plug. These factors cause deposits to form on the insulator nose which may result in trouble in operation. 000BA002 KN If engine is down on power, difficult to start or runs poorly at idling speed, first check the spark plug. : Remove spark plug as described in chapter "Starting / Stopping the Engine". : Clean dirty spark plug. : Check the electrode gap (A) and readjust if necessary - see "Specifications". : Use only resistor type spark plugs of the approved range. Rectify problems which have caused fouling of spark plug: : Too much oil in fuel mix. : Dirty air filter. : Unfavorable running conditions, e.g. operating at part load. Fit a new spark plug after approx. 100 operating hours or earlier if the electrodes are badly eroded. 40 FS 120, FS 120 R, FS 200, FS 200 R, FS 250, FS 250 R

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40
English / USA
FS 120, FS 120 R, FS 200, FS 200 R, FS 250, FS 250 R
Cutting tool rotates when engine is
idling
:
Turn idle speed screw (
LA
) slowly
counterclockwise until cutting tool
stops rotating and then turn the
screw about another
1
/
2
to 1turn in
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
1
/
4
turn)
until the engine runs and
accelerates smoothly.
Erratic idling behavior
Idle setting too rich:
:
Turn low speed screw (
L
) clockwise
(about
1
/
4
turn) until the engine runs
and accelerates smoothly.
Wrong fuel mix (too much engine oil in
the gasoline), a dirty air filter and
unfavorable running conditions (mostly
at part throttle etc.) affect the condition of
the spark plug. These factors cause
deposits to form on the insulator nose
which may result in trouble in operation.
If engine is down on power, difficult to
start or runs poorly at idling speed, first
check the spark plug.
:
Remove spark plug as described
in chapter "Starting / Stopping the
Engine".
:
Clean dirty spark plug.
:
Check the electrode gap (
A
) and
readjust if necessary – see
"Specifications".
:
Use only resistor type spark plugs
of the approved range.
Rectify problems which have caused
fouling of spark plug:
:
Too much oil in fuel mix.
:
Dirty air filter.
:
Unfavorable running conditions,
e.g. operating at part load.
Fit a new spark plug after approx.
100 operating hours
or earlier if the electrodes are badly
eroded.
Checking the Spark Plug
000BA002 KN