M-Tronic; Spark Arresting Screen In Muffler; Spark Plug - Stihl MS 661 C-M Instruction Manual

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M-Tronic

Basic information
M-Tronic regulates the fuel quantity and
ignition timing for all operating states
electronically.
M-Tronic stands for easy, fast starting,
constant optimum engine performance,
outstanding acceleration and automatic
adaptation to changes in operating
conditions.
Manual carburetor adjustments are no
longer required – the carburetor does
not have any adjusting screws.
Automatic adjustment
Under extremely changed operating
conditions, attainment of the optimal
setting can be accelerated as follows:
Carry out five uniform cuts to length
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under full load
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Spark Arresting Screen in
Muffler
If engine performance deteriorates,
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check the spark arresting screen in
the muffler
Let the muffler cool down
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1
2
3
Remove four screws
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Remove exhaust casing (1) of the
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muffler
Bend back the retaining lugs (2)
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Pull out spark arresting screen (3)
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Clean the dirty spark arresting
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screen, replace if damaged or
heavily carbonised
Refit the spark arresting screen in
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reverse order of steps

Spark Plug

If engine is down on power, difficult to
start or runs poorly at idling speed, first
check the spark plug.
Fit a new spark plug after approx. 100
operating hours or earlier if the
electrodes are badly eroded.
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.
Removing the spark plug
Turn the cap above the rear handle
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in the direction of the arrow and
remove the filter cover
MS 661 C-M