Service Tips; Wear Tolerances - Husqvarna 555FX Workshop Manual

Service tips

Defect:
Broken cooling fi ns, 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.

Wear tolerances

Cylinder bore
When the surface coating is
worn and aluminium appears.
Cylinder and piston
Piston ring gap
Max. 1.0 mm with the piston
ring inserted in the lower part of
the cylinder.
Action:
In severe cases – replace the cylinder.
Repair the threads using Heli-Coil.
Polish the damaged area using a fi ne 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 fi ne fi le of fi ne
grade emery cloth. Before the piston is refi tted 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 refi tting. 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.
Piston ring groove
Max. 1.6 mm. Clean the
groove before checking the
measurement.
Piston ring play
Max. 0.15 mm. Clean the
groove before checking the
measurement.
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