FS 110, FS 110 R
English
39
If engine is down on power, difficult to 
start or runs poorly at idling speed, first 
check the spark plug.
Fit a new spark plug after approx. 100 
operating hours or earlier if the 
electrodes are badly eroded.
Wrong fuel mix (too much engine oil in 
the gasoline), a dirty air filter and 
unfavorable running conditions (mostly 
at part throttle etc.) affect the condition 
of the spark plug. These factors cause 
deposits to form on the insulator nose 
which may result in trouble in operation.
Removing the spark plug
N Move the slide control to STOP-0.
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 Use only resistor type spark plugs of 
the approved range.
Rectify problems which have caused 
fouling of spark plug:
– Too much oil in fuel mix.
– Dirty air filter.
– Unfavorable running conditions, 
e.g. operating at part load.
Installing the spark plug
N Screw home the spark plug, fit the 
boot and press it down firmly.
Spark Plug
Warning!
To reduce the risk of fire and burn injury, 
use only spark plugs authorized by 
STIHL. Always press spark plug boot (1) 
snugly onto spark plug terminal (2) of 
the proper size. (Note: If terminal has 
detachable SAE adapter nut, it must be 
attached.) A loose connection between 
spark plug boot and ignition wire con-
nector in the boot may create arcing that 
could ignite combustible fumes and 
cause a fire.