Spark Arresting Screen In Muffler; Spark Plug - Stihl MS 251 C-Q Instruction Manual

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Spark Arresting Screen in
Muffler
If engine performance deteriorates,
N
check the spark arresting screen in
the muffler
Let the muffler cool down
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1
2
Unscrew the screw (1)
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Pull out spark arresting screen (2)
N
Clean the dirty spark arresting
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screen, replace if damaged or
heavily carbonized
Refit the spark arresting screen
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Fit screw
N
38

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
N
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
Remove the shroud – see "Shroud"
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Pull off the spark plug boot
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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.
–
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.
A
1
MS 251 C-Q