Wacker Neuson WM 90 User Manual

Sub Systems WM 90 Repair
wc_tx000390gb.fm 74
9.4 Automatic Decompression System
See Graphic: wc_gr001917
WM 90 engines employ an automatic decompression system as a
standard feature. This system enables easy starting of the engine, with
lighter recoil pull. The automatic decompression system releases the
compression of the engine by lifting up the exhaust valve at cranking
speeds.
At the end of the compression process, the release lever (a) lifts up the
tappet (b) which in turn opens the exhaust valve slightly to release
compression. The release lever has a flyweight (c) on one end and a
crescent cam (d) on the other. When the engine is cranked, the
crescent cam projects above the cam profile and lifts up the tappet
because the gravity force on the weight is larger than the centrifugal
force on the weight.
Reference: exhaust cam (e); camshaft (f); rotation direction (g).
See Graphic: wc_gr001918
When the cranking speed reaches a specified rpm, the crescent cam
(d) is retracted under the cam profile because the centrifugal force
applied to the flyweight (c) becomes larger than the force of the gravity
on the weight and thus it is shifted to the position shown.
wc_gr001917
a
b
c
d
e
e
f
g
wc_gr001918
a
b
c
d
e
e
f
g

Wacker Neuson WM 90 Specifications

General

Brand	Wacker Neuson
Model	WM 90
Category	Engine
Language	English