Stihl MS 171 User Guide - Page 23

Chain Brake, 7.1 Checking Operation, 7.2 Removing and Installing the Brake Band - chainsaw

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7. Chain Brake 7.1 Checking Operation The chain brake is one of the most important safety devices on the chainsaw. 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. This, in turn, reduces the frictional forces and thus 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. 7.2 Removing and Installing the Brake Band 1 - Troubleshooting, b 4.2 - Remove the chain sprocket cover, bar and chain, b 5 : Disengage the chain brake by pulling the hand guard (1) towards the front handle - the brake band is loose. - Remove the clutch drum, b 6.1 - Push the hand guard (1) towards the guide bar - the brake band is tensioned. To reduce the risk of injury, do not activate the chain brake while the chain brake cover is open. 533RA022 TG 1 : Pry the brake band (1) out of its seat (arrow). 1 : Swing the brake band (1) outwards. Do not over-stretch the brake band. 533RA028 TG 533RA027 TG The braking time is in order if deceleration of the saw chain is imperceptible to the eye. If the chain brake does not operate properly, refer to troubleshooting, b 4.2. 1 1 TOP 533RA356 TG 533RA029 TG : Use a screwdriver to ease the cover (1) away at the points shown (arrows). : Turn the brake band (1) slightly to one side and disconnect it from the brake lever (arrow). - Remove and inspect the cover (1), service or replace if necessary. 22 MS 171, MS 181, MS 211

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22
MS 171, MS 181, MS 211
7.
Chain Brake
7.1
Checking Operation
The chain brake is one of the most
important safety devices on the
chainsaw. 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.
This, in turn, reduces the frictional
forces and thus 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 is
imperceptible to the eye.
If the chain brake does not operate
properly, refer to troubleshooting,
b
4.2.
7.2
Removing and Installing
the Brake Band
– Troubleshooting,
b
4.2
–
Remove the chain sprocket
cover, bar and chain,
b
5
:
Disengage the chain brake by
pulling the hand guard (1)
towards the front handle – the
brake band is loose.
–
Remove the clutch drum,
b
6.1
–
Push the hand guard (1) towards
the guide bar – the brake band is
tensioned.
To reduce the risk of injury, do not
activate the chain brake while the
chain brake cover is open.
:
Use a screwdriver to ease the
cover (1) away at the points
shown (arrows).
–
Remove and inspect the cover
(1), service or replace if
necessary.
533RA022 TG
1
TOP
1
533RA356 TG
:
Pry the brake band (1) out of its
seat (arrow).
:
Swing the brake band (1)
outwards.
Do not over-stretch the brake band.
:
Turn the brake band (1) slightly to
one side and disconnect it from
the brake lever (arrow).
533RA027 TG
1
533RA028 TG
1
533RA029 TG
1