FT 250
English
26
N Carry out the standard setting.
N Warm up the engine.
N Turn high speed screw (H) slightly 
clockwise (leaner) – no further than 
stop.
NOTICE
After returning from high altitude, reset 
the carburetor to the standard setting.
If the setting is too lean there is a risk of 
engine damage due to insufficient 
lubrication and overheating.
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 off the engine.
N Pull off the spark plug boot (1).
N Unscrew the 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.
Spark Plug