WARNING
If the saw chain continues to keep rotating in idle
even after adjustment, have the chain saw
checked by a servicing dealer.
24.4.3 Speed erratic when idling; poor accel‐
eration (despite standard setting of low
speed adjusting screw)
The idle setting is too lean.
► Carefully turn the low speed adjusting
screw (L) counterclockwise until the engine
runs and accelerates smoothly – but no further
than the stop
Whenever the low speed adjusting screw (L) has
been adjusted, it is usually also necessary to
readjust the idle speed adjusting screw (LA).
24.5 Correcting the carburetor set‐
ting for use at high altitudes
The setting may have to be marginally corrected
if engine performance is unsatisfactory at high
altitudes:
► Make standard setting
► Let the engine warm up
► Turn the high speed adjusting screw (H)
slightly clockwise (leaner) – max. up to the
stop
NOTICE
After descending from a high altitude, restore the
carburetor setting to the standard setting.
If you make the setting too lean it will increase
the risk of engine damage through lack of lubri‐
cation and overheating.
25 Spark Plug
► If the engine is down on power, difficult to start
or runs poorly at idle speed, first check the
spark plug.
► 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 "Specifica‐
tions".
25.1 Removing the spark plug
► Remove the shroud – see "Shroud".
► Move the Master Control lever to the stop
position (0).
► Pull off the spark plug boot.
► Clean away loose dirt from around the spark
plug.
► Insert the combination wrench through the
grommet (1) and turn it as necessary to
engage the spark plug's hexagon.
► Push the combination fully home against the
cylinder.
► Unscrew the spark plug.
25.2 Checking the Spark Plug
► Clean dirty spark plug.
► Check electrode gap (A) and readjust if neces‐
sary – see "Specifications".
► Rectify the problems which have caused foul‐
ing of the spark plug.
Possible causes are:
–
Too much oil in fuel mix.
–
Dirty air filter.
–
Unfavorable running conditions.
English 25 Spark Plug
32 0458-574-0121-D
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