Spark Plug - Stihl MS 381 Instruction Manual

English
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Fine Tuning for Operation at High
Altitude
A slight correction of the setting may be
necessary if engine does not run
satisfactorily:
Carry out the standard setting.
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Warm up the engine.
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Turn high speed screw (H) slightly
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clockwise (leaner) – no further than
stop.
NOTICE
After returning from high altitude, reset
the carburetor to the standard setting.
If the setting is too lean there is a risk of
engine damage due to insufficient
lubrication and overheating.
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Spark Plug

If the engine is down on power,
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difficult to start or runs poorly at idle
speed, first check the spark plug.
Fit a new spark plug after about 100
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operating hours – or sooner if the
electrodes are badly eroded. Install
only suppressed spark plugs of the
type approved by STIHL – see
"Specifications".
Removing the Spark Plug
Set the Master Control lever (1) to F
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3
2
1
Loosen the twist lock (2) in the
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direction of the arrow.
Remove the carburetor box
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cover (3).
Pull off the spark plug boot.
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Unscrew the spark plug.
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Checking the spark plug
Clean dirty spark plug.
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Check electrode gap (A) and
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readjust if necessary – see
"Specifications".
Rectify the problems which have
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caused fouling of the spark plug.
Possible causes are:
Too much oil in fuel mix.
–
Dirty air filter.
–
Unfavorable running conditions.
–
A
MS 381