Chain Brake; Checking Operation; Removing And Installing The Brake Band - Stihl MS 240 Instruction Manual

7.

Chain Brake

7.1

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.
– Start 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 (less
than a second) is imperceptible to
the eye.
The chain must come to a standstill
in less than a second.
If the chain brake does not operate
properly, refer to troubleshooting,
b 4.2.
MS 240, MS 260, MS 260 C
7.2 Removing and Installing
the Brake Band
: Disengage the chain brake by
pulling the hand guard (1)
towards the front handle.
The brake band is no longer under
tension.
– Remove the clutch drum, b 6.1
– Troubleshooting, b 4.2
– Remove the sprocket cover and
cutting attachment, b 5
: Take out the screw (arrow) and
remove the side plate (1).
Versions with Quick Chain
Tensioner
1
: Take out the screw (arrow) and
remove the side plate (1).
: Remove the upper bumper strip
(2).
1
: Take out the screws (arrows).
On versions with handle heating
– Remove the ground wire,
b 15.4.1.
1
: Remove the cover (1).
2
1
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