Instruction Manual

MS 231, MS 231 C, MS 251, MS 251 C
English
37
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 Remove the shroud – see "Shroud"
N Pull off the spark plug boot
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 Fit spark plug by hand
N Tighten the spark plug and press on
the spark plug boot firmly
N Fit the shroud – see "Shroud"
Spark Plug
2310BA006 KN
000BA039 KN
A
1
000BA045 KN
2310BA012 KN