Chain Brake; Checking Operation; Brake Band - Stihl MS 201 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.
The braking time is in order if
deceleration of the saw chain is
imperceptible to the eye (a fraction
of a second).
If the chain brake does not operate
properly, refer to troubleshooting,
b 3.2.
20
5.2

Brake Band

– Troubleshooting, b 3.2
– Disengage the chain brake and
remove the chain sprocket cover,
bar and chain.
: Take out the screws (arrows).
: Ease the cover (1) out of its seat
(arrow) and lift it away.
: Pry the brake band (1) out of its
seat (arrow).
1
: Swing the brake band (1)
outwards and disconnect it from
the brake lever (arrow).
: Do not over-stretch the brake
band.
1
Install a new brake band if there are
noticeable signs of wear (large
areas on inside diameter and/or
parts of outside diameter – arrows)
and its remaining thickness is less
than 0.6 mm.
1
MS 201, MS 201 C, MS 201 T, MS 201 TC