Husqvarna 343R, 345RX, 343F, 345FX, 345FXT Piston scoring caused by heavy carbon deposits, Cause

6 Cylinder and piston

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.

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:		Action:
• Incorrect oil mixture in the fuel.		Change to a fuel with the correct oil
		mixture.
• Too low octane fuel.		Change to a higher octane petrol.
•	Air leaks.	Replace damaged parts.
	Cracked fuel hose.
	Leaking inlet gaskets.
	Cracked distance piece or inlet
	manifold.
• Air leakage in engine body.		Replace leaking gaskets and shaft
	Leaking crankshaft seals.	seals.
	Leaking cylinder and crankcase
	gaskets.
•	Poor maintenance.	Clean the cooling fins and air intake.
	Dirty cooling fins on the cylinder.
	Blocked air intake on the starter.
	Blocked spark arrestor mesh in	Clean or replace the spark arrestor
	the muffler.	mesh.

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 combustion 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:	Action:
• Wrong type of two-stroke oil or	Change the fuel.
petrol.
• Incorrect oil mixture in the petrol.	Change to a fuel with the correct oil
	mixture.
• Incorrect carburettor setting.
	Correct the carburettor setting

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