Spark Plug - Stihl FS 40 Instruction Manual

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
Shut off the engine.
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1
2
Remove the spark plug boot (1).
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Unscrew the spark plug (2).
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FS 40, FS 40 C, FS 50, FS 50 C
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.
–
WARNING
Arcing may occur if the adapter nut (1) is
loose or missing. Working in an easily
combustible or explosive atmosphere
may cause a fire or an explosion. This
can result result in serious injuries or
damage to property.
Use resistor type spark plugs with a
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properly tightened adapter nut.
Installing the Spark Plug
Screw the spark plug into the
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cylinder.
Press the boot firmly onto the spark
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plug.
A
1
English
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