Winter Operation; Checking The Spark Plug - Stihl FS 500 Instruction Manual

English / USA

Winter Operation

Change the air intake to the winter mode
to help prevent air filter and carburetor
icing at temperatures below 50°F
(+10°C).
: Pull out the plug, turn it around and
refit it so that the openings face the
clutch housing.
Change the air intake back to the
summer mode when the outside
temperature is above 70°F (+20°C):
: Pull out the plug, turn it around and
refit it so that the openings face
outward.
32

Checking the Spark Plug

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 – see "Starting /
Stopping the Engine".
: Clean dirty spark plug.
: Check 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.
FS 500, FS 550