Spark Arresting Screen In Muffler - Stihl MS 391 Safety Manual

N
Turn the high speed screw (H)
counterclockwise as far as stop (no
more than 3/4 turn).
N
Turn the low speed screw (L)
carefully clockwise as far as stop,
then turn it back 1 full turn.
Adjusting idle speed
Engine stops while idling
N
Open the low speed screw (L) one
full turn.
N
Turn the idle speed screw (LA)
clockwise until the chain begins to
run – then back it off 1 1/2 turns.
Chain runs when engine is idling
N
Open the low speed screw (L) one
full turn.
N
Turn the idle speed screw (LA)
counterclockwise until the chain
begins to run – then turn it another
1 1/2 turns in the same direction.
If the chain continues moving
when the engine is idling, have
your saw checked and repaired by
your servicing dealer.
Erratic idling behavior, poor
acceleration (even though low speed
screw is open one turn)
N
Idle setting is too lean: Turn the low
speed screw (L) counterclockwise
until the engine runs and
accelerates smoothly.
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
MS 311, MS 391
Fine tuning for operation at high
altitude
A slight correction of the setting may be
necessary if the engine does not run
satisfactorily:
N
Turn high speed screw (H)
clockwise (leaner) – no further than
stop.
If the setting is too lean there is a
risk of engine damage due to
insufficient lubrication and
overheating.
Spark Arresting Screen in
Muffler
In some countries the muffler is
equipped with a spark arresting screen.
N
If the engine is down on power,
check the spark arresting screen in
the muffler.
N
Wait for the muffler to cool down.
1
2
N
Take out the screw (1).
N
Pull out the spark arresting
screen (2).
N
Clean the spark arresting screen. If
the screen is damaged or heavily
carbonized, fit a new one.
N
Refit the spark arresting screen.
N
Insert the screw and tighten it down.
English
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