Husqvarna 129C Workshop Manual page 49

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 too tight in the aluminium material.
Wear tolerances
Cylinder bore
When the surface coating
is worn and aluminium
appears.
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 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.
Piston ring groove
Max. 1.6 mm. Clean the
groove before checking the
measurement.
Cylinder and piston
Piston ring play
Max. 0.15 mm. Clean the
groove before checking the
measurement.
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