Analysis And Actions - Husqvarna 122 HD60 Workshop Manual

6
Small to medium size scores primarily in the
middle of the exhaust port.
Medium to deep scores along the entire
piston skirt on the exhaust side.
36
Cylinder and piston

Analysis and actions

Experience tells us that piston or cylinder failure due to manufacturing errors are
extremely rare.
The reason is usually due to other factors, which is evident from the following.
Note the reasons for the breakdown, repair the damage and take the actions required to
prevent the same thing happening again.
Insuffi cient lubrication
The piston has small to medium size score marks usually in front of the exhaust port. In
extreme cases heat development can be so great that material from the piston smears
along the piston skirt and even in the cylinder bore.
Generally the piston ring is undamaged and moves freely in the ring groove
There can also be scores on the inlet side of the piston.
Cause:
• Incorrect carburettor setting.
Recommended max. speed exceeded.
• Incorrect oil mixture in the fuel.
• Too low octane fuel.
The piston ring starts to stick or is completely stuck in its groove and has therefore
not been able to seal against the cylinder wall, which has resulted in further, intensive
temperature increases in the piston
Seizure scores along the entire piston skirt on the inlet and exhaust sides.
Cause:
• Incorrect oil mixture in the fuel.
• Too low octane fuel.
• Air leaks.
Cracked fuel hose.
Leaking inlet gaskets.
Cracked distance piece or inlet
manifold.
• Air leakage in engine body.
Leaking crankshaft seals.
Leaking cylinder and crankcase
gaskets.
• Poor maintenance.
Dirty cooling fi ns on the cylinder.
Blocked air intake on the starter.
Blocked spark arrestor mesh in the
muffl er.
For the best results we recommend Husqvarna two-stroke oil or ready-mixed fuel that is
specially developed for air-cooled two-stroke engines.
Mixing ratio: 1:50 (2%).
If Husqvarna two-stroke oil is not available another good quality two-stroke oil can be
used.
Mixing ratio: 1:33 (3%) or 1:25 (4%).
Check and change the carburettor setting.
Change the fuel.
Change to a fuel with the correct oil mixture.
Replace damaged parts.
Replace leaking gaskets and shaft seals.
Clean the cooling fi ns and air intake.
Clean or replace the spark arrestor mesh.