Instruction Manual

MS 661 C-M
English
35
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
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.
N Use resistor type spark plugs with a
properly tightened adapter nut.
Installing the spark plug
N Screw in the spark plug
N Press on the spark plug boot (1)
firmly
N Mount filter cover
Spark Plug
1166BA011 AM
1166BA018 AM
1
000BA039 KN
A
1
000BA045 KN
1166BA018 AM
1