Operation Manual
34
English / USA
HT 100, HT 101, HT 130, HT 131
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.
If engine is down on power, difficult to 
start or runs poorly at idling speed, first 
check the spark plug.
: Remove spark plug as described 
in chapter "Starting / Stopping the 
Engine".
: Clean dirty spark plug.
: Check the electrode gap (A) and
readjust if necessary – see 
"Specifications".
: 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.
Fit a new spark plug after approx. 
100 operating hours 
or earlier if the electrodes are badly 
eroded.
To reduce the risk of fire and burn 
injury, use only spark plugs 
authorized by STIHL. Always press 
spark plug boot (2) snugly onto 
terminal (1) 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 connector in the boot 
may create arcing that could ignite 
combustible fumes and cause a fire.
Checking the Spark Plug
000BA002 KN
1
2
002BA071 KN










