Spark Plug - Stihl FS 85 Instruction Manual

20 Spark Plug

WARNING
Adjust the high speed screw (H) only if you are
using a mowing head, making sure the cutting
lines are full length (as far as the line limiter
blade on the deflector).
If a metal cutting attachment is mounted, use the
standard setting and adjust the high speed
screw (H) as described above under "Rule of
thumb".
► Carry out the standard setting.
► Start the engine and, with the mowing head
mounted, warm it up for about 3 minutes.
► Open the throttle wide.
19.2.1 At high altitude
► Turn the high speed screw (H) clockwise
(leaner), no further than stop, until there is no
noticeable increase in engine speed.
19.2.2 At sea level
► Turn the high speed screw (H) counterclock‐
wise (richer), no further than stop, until there is
no noticeable increase in engine speed.
It is possible that maximum engine speed may
be reached with the standard setting in each
case.
19.3 Adjust idle speed
It is usually necessary to change the setting of
the idle speed screw (LA) after every correction
to the low speed screw (L).
► Warm up the engine.
19.3.1 Engine stops while idling
► Turn the idle speed screw (LA) slowly clock‐
wise until the engine runs smoothly – the cut‐
ting attachment must not run.
19.3.2 Cutting attachment runs when engine
is idling
► Turn the idle speed screw (LA) counterclock‐
wise until the cutting attachment stops moving
and then rotate the screw another 1/2 to 1 turn
in the same direction.
0458-393-8721-C
WARNING
If the cutting attachment continues to run when
the engine is idling, have your machine checked
and repaired by your servicing dealer.
19.3.3 Erratic idling behavior, engine stops
even though setting of LA screw has
been corrected, poor acceleration
Idle setting is too lean
► Idle setting is too lean: Rotate the low speed
screw (L) about 1/4 turn counterclockwise until
the engine runs and accelerates smoothly.
19.3.4 Erratic idling behavior
Idle setting is too rich:
► Rotate the low speed screw (L) about 1/4 turn
clockwise until the engine runs and acceler‐
ates smoothly.
20 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".
20.1 Removing the Spark Plug
► Move the slide control to STOP-0.
► Pull off the spark plug boot (1).
► Unscrew the spark plug.
English
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