The saga continues (scored piston). Husqvarna 350

[gregc]

Hi Folks,

I recently replaced the top end of my Husqvarna 350. New cylinder and piston. I was cutting some 18 inch rounds today (elm and poplar I think) and the saw was zipping right through when the muffler fell off. The new piston showed some slight scoring. I haven't taken it apart to check the ring but the piston seems pretty tight and the compression is ok.

The saw is running to spec for idling and max rpms. The compression reads low (130) but I think my gauge might be messed up. I'll probably take it to the mower shop and have them look too.

Can anyone speculate as to why this piston may have scored so quickly? Debris in the crankcase (maybe when the muffler fell off)? Cheap aftermarket piston? To lean a mix? The saw cuts like the devil, runs smooth, starts up fine and isn't running hot. Can I still keep using it or should I do something? Also, whats a good way to hold the muffler on tight? (I tried blue locktite which doesn't seem to work very well.

Thanks so much.

Greg

 

[discounthunter]

if the muffler came off ,it could have been loose for a while,possibly ingested some sawdust.

 

[rmh3481]

Once the muffler loosens up you lose all the back pressure keeping the fuel charge in the cylinder. The engine runs lean, lubrication breaks down, heat increases and the cylinder and piston score. This is why the muffler mod threads say to enrich the high side of the carb because of the loss of back pressure.