Husqvarna R135 Workshop Manual page 49

6
Medium to deep scores along the entire piston
skirt on the exhaust side.
Medium to deep scores on the exhaust side.
The piston ring is stuck in the groove.
Black discoloration under the piston ring due to
blow-by.
48
Cylinder and piston
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%).
Piston scoring caused by heavy carbon deposits
Too heavy carbon depositing can cause damage similar to that caused by insuffi cient
lubrication. However, the piston skirt has a darker colour caused by the hot combus-
tion gases that are blown past the piston.
This type of piston damage starts at the exhaust port where carbon deposits can
become loose and get trapped between the piston and the cylinder wall.
Typical for this type of piston damage is brown or black discoloration of the piston
skirt.
Cause:
• Wrong type of two-stroke oil or pet-
rol.
• Incorrect oil mixture in the petrol.
• Incorrect carburettor setting.
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 fi ns and air intake.
Clean or replace the spark arrestor
mesh.
Action:
Change the fuel.
Change to a fuel with the correct oil
mixture.
Correct the carburettor setting