Husqvarna 525P4S Workshop Manual page 56

Repair instructions
Larger, harder particles that enter the engine
cause serious damage to the underside of the
piston skirt.
Cause:
Air filter damaged or
missing.
Parts from the carbure-
tor or intake system
have come loose and
entered the engine.
Service tips
Defect:
Broken cooling fins, damaged threads or sheared
bolts by the exhaust port.
Seizure marks in the cylinder bore (especially by
the exhaust port).
Surface coating in the cylinder bore worn out
(primarily at the top of the cylinder).
The piston shows signs of seizure score marks
Piston ring burnt in its groove.
Bolts much too tight in the aluminium material.
56
- English
Action:
Fit a new air filter.
Regular service and
inspection.
Action:
In severe cases – replace the cylinder.
Repair the threads using Heli-Coil.
Polish the damaged area using a fine grade
emery cloth so that the coating of aluminium
disappears.
With deep seizure score marks the piston and
cylinder should be replaced.
Replace the cylinder and piston.
Carefully polish the damaged area using a fine
file of fine grade emery cloth. Before the piston
is refitted the cylinder should be polished as
above. With deep score marks the piston and
cylinder should be replaced.
Carefully loosen the piston rings and clean the
groove well before refitting. Carbon deposits in
the groove impair the important heat transfer
between the piston and cylinder.
NOTE!
Be careful with the lower edge of the piston
ring groove. If this is damaged, or if carbon
deposits remain, the compression pressure
can leak through.
Check the wear on the piston ring by placing it
in the lower part of the cylinder.
Position a suitable punch on the bolt head and
give a few sharp knocks with a hammer. If the
bolt still does not loosen, repeat the procedure.