Winter Operation - Stihl MS 391 Instruction Manual

English
felling cut. The chain brake will operate
only if it has been properly maintained
and the hand guard has not been
modified in any way.
Check operation of chain brake
Before starting work: Run engine at idle
speed, engage the chain brake (push
hand guard toward bar nose).
Accelerate up to full throttle for no more
than 3 seconds – the chain must not
rotate. The hand guard must be free
from dirt and move freely.
Chain brake maintenance
The chain brake is subject to normal
wear. It is necessary to have it serviced
and maintained regularly by trained
personnel, such as your STIHL servicing
dealer, at the following intervals:
Full-time usage:
Part-time usage:
Occasional usage:
34

Winter Operation

Remove shroud
Move the Master Control lever to the
N
stop position 0
Push the hand guard forwards – the
N
saw chain is blocked
1
every 3
Loosen screws (1)
N
months
Remove the shroud (2)
every 6
N
months
Pre-heat carburetor
every 12
months
At temperatures below +50 °F (+10 °C)
Pull the slide (1) out of the
N
position s (summer operation)
1
2
1
1
Place the slide in the position r
N
(winter operation) – r facing
upwards
Refit the shroud and tighten the
N
screws
Heated air is now drawn in from around
the cylinder and circulates around the
carburetor – this helps prevent
carburetor icing.
At temperatures above +70 °F (+20 °C)
Ensure that the slide is set back to
N
position s (summer operation)
without fail, otherwise the engine
may malfunction due to overheating
At temperatures below +14 °F (-10 °C)
Under extreme winter conditions
(temperatures below +14 °F (-10 °C),
powdered or drifting snow), it is
recommended to use the "cover plate
mounting kit" (special accessory).
In case of erratic idling behavior or poor
acceleration
Turn the low speed screw (L)
N
1/4 turn counterclockwise
MS 311, MS 391