Chain Brake; Checking Operation; Brake Band - Stihl MS 231 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 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.
20
All manuals and user guides at all-guides.com
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
2
1
: Take out the screws (1).
: Remove the cover (2).
– Engage the chain brake.
1
: 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
1
: Turn the brake band (1) to one
side and disconnect it from the
brake lever (2).
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.
2
MS 231, MS 231 C, MS 251, MS 251 C
2
1