Analysis And Actions - Husqvarna 125C Workshop Manual

6
Cylinder, piston, crankshaft, crankcase
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.
40

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.
Insufficient 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 ex-
ceeded.
• 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 fins on the cylinder.
Blocked air intake on the starter.
Blocked spark arrestor mesh in
the muffler.
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%).
Action:
Check and change the carburettor
setting.
Change the fuel.
Change to a higher octane petrol.
Action:
Change to a fuel with the correct oil
mixture.
Change to a higher octane petrol.
Replace damaged parts.
Replace leaking gaskets and shaft
seals.
Clean the cooling fins and air intake.
Clean or replace the spark arrestor
mesh.