Husqvarna 531RS Workshop Manual page 48

Cylinder and piston
4. Failure of the crankshaft bearing or on the
connecting rod bearing is usually caused by a too
high engine speed, resulting in the bearing being
overloaded or overheating. This in turn can cause
the bearing rollers or ball to glide instead of rotate,
which can cause the roller or ball retainer to break.
The broken debris can be trapped between the pis-
ton and cylinder wall, damaging the piston skirt.
Debris can also pass up through the cylinder's
transfer channels and cause damage to the top and
sides of the piston as well as to the cylinder's com-
bustion chamber. See Figure 12.
Foreign objects
Everything other than clean air and pure fuel that enters
the engine's inlet port causes some type of abnormal
wear or damage to the cylinder and piston.
This type of increased wear shows on the piston's inlet
side starting at the lower edge of the piston skirt.
The damage is caused by badly filtered air that passes
through the carburettor and into the engine.
1. Small score marks and a matt, grey surface on the
piston's inlet side caused by fine dust particles. See
Figure 13.
2. Inlet side. Particles of dust and dirt from carbon-like
deposits on the top of the piston and in the piston ring
groove. The piston ring sits firmly in the groove. Piston
material has been worn away. The lower part of the pis-
ton skirt is thinner on the inlet side than on the exhaust
side. See Figure 14.
Cause
Faulty air filter. Small dust
particles pass through the
filter.
The filter is worn out due
to too much cleaning,
whereby small holes have
appeared in the material.
Unsuitable filter mainte-
nance, such as wrong
method or wrong clean-
ing agent. Flock material
becomes loose and holes
appear.
48 - English
Action
Fit a finer grade filter.
Check the filter carefully
for holes and damage
after cleaning. Replace
the filter if necessary.
Clean more carefully
and use the right clean-
ing agent (such as tepid
soapy water). Change the
filter.
Fig. 12
Fig. 13
Fig. 13