Instruction Manual

MS 661 C-M
English
34
N If engine performance deteriorates,
check the spark arresting screen in
the muffler
N Let the muffler cool down
N Remove four screws
N Remove exhaust casing (1) of the
muffler
N Bend back the retaining lugs (2)
N Pull out spark arresting screen (3)
N Clean the dirty spark arresting
screen, replace if damaged or
heavily carbonised
N Refit the spark arresting screen in
reverse order of steps
N If the engine is down on power,
difficult to start or runs poorly at idle
speed, first check the spark plug.
N Fit a new spark plug after about 100
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
N Turn the cap above the rear handle
in the direction of the arrow and
remove the filter cover
N Unplug spark plug boot (1)
N Unscrew spark plug
Checking the spark plug
N Clean dirty spark plug.
N Check electrode gap (A) and
readjust if necessary – see
"Specifications".
N Rectify the problems which have
caused fouling of the spark plug.
Possible causes are:
– Too much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions.
WARNING
If the spark plug comes with a
detachable adapter nut (1), screw the
adapter onto the thread and tighten it
down firmly to reduce the risk of arcing
and fire.
Spark Arresting Screen in
Muffler
1
1166BA016 AM1166BA017 AM
2
3
Spark Plug
1166BA011 AM
1166BA018 AM
1
000BA039 KN
A
1
000BA045 KN