Chain Brake; Checking Operation; Removing And 9. Installing - Stihl MS 290 Manual

1
: Push cover washer (1), "TOP"
(arrow) facing outward, onto the
crankshaft.
: Screw on the clutch and tighten it
down firmly, b 3.5
Install all other parts in the reverse
sequence.
: If terminal of spark plug has a
detachable adapter nut, make
sure it is tightened down firmly.
18
5.6

Chain Brake

5.6.1

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. The shorter the braking
time, the better the efficiency and
protection offered against being
injured by the rotating chain.
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.
5.6.2 Removing and Installing
– Remove the clutch drum/chain
sprocket, b 5.1
– Relieve tension of brake spring
by pushing hand guard forward.
2
: Remove the bumper strip (1).
: Take out the screws (arrows).
: Remove the cover (2).
: Carefully ease the brake spring
off the anchor pin.
– If the groove in the anchor pin is
worn, install a new pin, b 5.7.1
MS 290, MS 310, MS 390
1