BT 121
English
16
If the engine is down on power, difficult
to start or runs poorly at idle speed, first
check the spark plug.
N
Remove the spark plug, see
"Starting / Stopping the Engine".
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.
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".
To reduce the risk of arcing and fire
If the spark plug comes with a
detachable adapter nut:
N
Screw the adapter nut (1) onto the
thread and tighten it down firmly.
On all spark plugs
N
Always press the boot (2) firmly on
to the spark plug (3).
Checking the Spark Plug
000BA002 KN
1
000BA045 KN
3
002BA178 KN
2