FS 55, FS 55 C, FS 55 R, FS 55 RC
English
34
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.
If engine running behavior is 
unsatisfactory even though the air filter 
is clean and the carburetor is properly 
adjusted, the cause may be the muffler.
Have the muffler checked for 
contamination (carbonization) by your 
servicing dealer.
STIHL recommends that you have 
servicing and repair work carried out 
exclusively by an authorized STIHL 
servicing dealer.
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.
Engine Running Behavior