Chain Brake; Checking Operation; Brake Band - Stihl MS 261 User Manual

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 interlock lever is
depressed.
With the coasting brake
disengaged, open the throttle wide
and let go of the interlock 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.
MS 261, MS 261 C
5.2

Brake Band

– Remove the clutch drum, b 4.1
– Troubleshooting, b 3.2
1
: Take out the screw (arrow) and
remove the side plate (1).
Machines with Quick Chain
Tensioner
1
: Take out the screw (arrow) and
remove the side plate (1).
2 1
2
: Take out the screws (2).
: Remove the cover (1).
1
– Engage the chain brake.
– Brake band no longer
tensioned in its seat.
: Remove the screw (1) from the
underside of the machine.
1
: Pry the brake band (1) out of its
seat (arrow).
– Remove the brake band (1).
Do not overstretch the brake band.
– Disengage the chain brake
2 – the brake band can be
disconnected when the brake
lever is in this position.
21