Husqvarna 343R, 345RX, 343F, 345FX, 345FXT Foreign objects, Cylinder and piston, Cause, Action

6 Cylinder and piston

Small score marks and a matt, grey surface on the piston’s inlet side caused by fine dust particles.

Foreign objects

Everything other than clean air and pure fuel that enters the engine’s inlet port causes some type of abnormal wear or damage to the cylinder and piston.

This type of increased wear shows on the piston’s inlet side starting at the lower edge of the piston skirt.

The damage is caused by badly filtered air that passes through the carburettor and into the engine.

Inlet side.

Particles of dust and dirt from carbon-like deposits on the top of the piston and in the piston ring groove. The piston ring sits firmly in the groove. Piston material has been worn away.

The lower part of the piston skirt is thinner on the inlet side than on the exhaust side.

Cause:

•Faulty air filter. Small dust particles pass through the filter.

•The filter is worn out due to too much cleaning, whereby small holes have appeared in the material.

•Unsuitable filter maintenance, such as wrong method or wrong cleaning agent. Flock material becomes loose and holes appear.

•Air filter incorrectly fitted.

•Air filter damaged or missing.

Action:

Fit a finer grade filter.

Check the filter carefully for holes and damage after cleaning. Replace the filter if necessary.

Clean more carefully and use the right cleaning agent (such as tepid soapy water).

Change the filter. Fit the filter correctly. Fit a new air filter.

The piston scored and worn from the piston ring down on the inlet side.

Larger, softer particles that penetrate into the engine cause damage to the piston skirt under the piston ring as the illustration shows.

Cause:		Action:
•	Air filter incorrectly fitted.	Fit the air filter correctly.
•	Air filter damaged or missing.	Fit a new air filter.

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