20 MS 271 C, MS 291 C
5. Chain Brake
5.1 Checking Operation
The chain brake is one of the most
important safety devices on the
chain saw. Its efficiency is
measured in terms of the chain
braking time, i.e. the time that
elapses between activating the
brake and the saw chain coming to
a complete standstill.
Contamination (with chain oil, chips,
fine particles of abrasion, etc.) and
smoothing of the friction surfaces of
the brake band and clutch drum
impair the coefficient of friction,
which prolongs the braking time. A
fatigued or stretched brake spring
has the same negative effect.
– Starting the engine
– With the chain brake activated
(locked), open the throttle wide
for a brief period
(max. 3 seconds) – the chain
must not rotate.
– With the chain brake released,
open the throttle wide and
activate the brake manually – the
chain must come to an abrupt
stop.
Machines with QuickStop Super
The clutch drum must rotate freely
when the lockout lever is
depressed.
With the coasting brake
disengaged, open the throttle wide
and let go of the lockout lever on the
rear handle – the chain must come
to an abrupt stop.
All models
The braking time is in order if
deceleration of the saw chain (less
than a second) is imperceptible to
the eye.
If the chain brake does not operate
properly, refer to troubleshooting,
b
3.2.
5.2 Brake Band
– Remove the clutch drum, b
4.1
– Troubleshooting, b
3.2
Machines with Quick Chain
Tensioner
: Take out the screw (arrow) and
remove the side plate (1).
All models
: Take out the screws (2).
: Remove the cover (1).
2710RA008 TG
off
off
1
off
off
off
2710RA009 TG
1
2
2
2
– Engage the chain brake.
: Remove the screw (1) from the
underside of the machine.
: Pry the brake band (2) out of its
seat (arrow).
– Remove the brake band without
overstretching it.
– Disengage the chain brake
: Turn the brake band (1) to one
side and disconnect it from the
brake lever (2).
2710RA010 TG
1
2
off
2710RA012 TG
1
2
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