Adjusting The Carburetor; Spark Arresting Screen In Muffler; Spark Plug - Stihl FC 91 Manual De Instrucciones

Adjusting the Carburetor

The carburetor has been set at the
factory to provide an optimum fuel-air
mixture under most operating
conditions.
Adjusting Idle Speed
Engine stops while idling
Warm up the engine for about
N
3 minutes.
Turn the idle speed screw (LA)
N
slowly clockwise until the engine
runs smoothly – the cutting
attachment must not run.
Cutting attachment runs when engine is
idling
Turn the idle speed screw (LA)
N
slowly counterclockwise until the
cutting attachment stops running
and then turn the screw about
another 1/2 to 3/4 turn in the same
direction.
WARNING
If the cutting attachment continues to run
when the engine is idling, have your
machine checked and repaired by your
servicing dealer.
FC 91
Spark Arresting Screen in
Muffler
If the engine is down on power,
N
check the spark arresting screen in
the muffler.
Wait for the muffler to cool down.
N
4
5
Take out the screw (4).
N
Lift the spark arresting screen (5)
N
and pull it out.
Clean the spark arresting
N
screen (5). If the screen is damaged
or heavily carbonized, install a new
one.
Refit the spark arresting screen (5).
N
Insert the screw (4) and tighten it
N
down firmly.

Spark Plug

If there is a loss of engine power, the
machine is difficult to start or runs poorly
at idle, first check the spark plug.
Install a new spark plug after
approximately 100 operating hours or
earlier if the electrodes are
eroded/corroded.
The 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 degrade performance.
Removing the Spark Plug
1
2
3
Remove the cover (1).
N
Pull off the spark plug boot (2).
N
Unscrew the spark plug (3).
N
English
23