Spark Plug - Stihl MS 440 Instruction Manual

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 the high speed screw (H)
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slightly clockwise (leaner). On
carburetors with H = 3/4, turn 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.
MS 440

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
Move the master control lever to the
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stop position 0
Turn the knob above the rear handle
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in the direction of the arrow and
remove the carburetor box cover
1
Remove air filter (1) (versions with
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box filter)
Unplug spark plug boot (2)
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Unscrew 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.
–
English
2
A
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