Instruction Manual

MS 311, MS 391
English
42
It is usually necessary to change the
setting of the idle speed screw (LA) after
every correction to the low speed
screw (L).
Fine tuning for operation at high altitude
A slight correction of the setting may be
necessary if engine does not run
satisfactorily:
N Carry out the standard setting.
N Warm up the engine.
N Turn high speed screw (H) slightly
clockwise (leaner) – no further than
stop.
NOTICE
After returning from high altitude, reset
the carburetor to the standard setting.
If the setting is too lean there is a risk of
engine damage due to insufficient
lubrication and overheating.
N If the engine is down on power,
check the spark arresting screen in
the muffler.
N Wait for the muffler to cool down.
N Take out the four screws.
N Remove the muffler exhaust
casing (1).
N Bend back the retaining tabs (2).
N Pull out the spark arresting
screen (3).
N Clean the spark arresting screen. If
the screen is damaged or heavily
carbonized, fit a new one.
N Refit the spark arresting screw in
the reverse sequence.
If engine is down on power, difficult to
start or runs poorly at idling speed, first
check the spark plug.
Fit a new spark plug after approx. 100
operating hours or earlier if the
electrodes are badly eroded.
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.
Remove the spark plug
N Move the Master Control lever to the
stop position 0
N Push the hand guard forwards – the
saw chain is blocked
N Loosen screws (1)
N Remove the shroud (2)
Spark Arresting Screen in
Muffler
0001BA043 KN
3
2
0001BA044 KN
Spark Plug
1
4903BA002 KN
1
1
2