Husqvarna 357XP

[jpilk99]

My wonderful 357XP hit a speed bump recently. Wasn't running well, and I replaced the carb with a good one. Still wasn't running well ...and I checked compression and it was only 105psi. So I bought a new piston & rings. Gave it a good bath of mystery oil prior to starting, and cranked it over with no spark plug... She started and ran GREAT. For 2 minutes. It shut down immediately - as if I had hit the kill switch/turned it off.

I thought the rings might be "settling in" so I let it sit for a day or two. Tried again, and some thing - 2 minutes of great running and then abrupt stop. I checked the ignition coil and my tester lit right up. I tested the spark plug and it wasn't great, so I put in a new one. I let it cool down and went back and tried again, and nothing. Waited another few hours, still nothing. Even a little starter fluid down the spark plug hole - zilch. Checked compression, and it was about 55psi.

Pulled the head and piston was scored pretty well, on the exhaust side. Rings were stuck in. I also notice, both times when it ran, that it seemed to smoke. I thought it was just oily residue burning off the engine. Now I'm thinking it was running to hot, either lean or ....maybe the crank seal has "left the building".

I can get another piston, re-hone the cylinder, and try again ...but without knowing what happened to this setup, I'm likely destined to repeat it.

Any thoughts?

Thanks all!

Jay

 

[Bob Hedgecutter]

Yes- you will keep destroying top ends as long as you keep buying and bolting them on.
Pressure and vacuum test before tear down- repeat test after rebuild.
My guess is it is running excessively lean and sucking air from somewhere outside the system.

Intake boot if a classic on these- especially if held to the cylinder with the plastic clip.
Small right angle impulse line is also often missed as a culprit- but it can be any one thing, or a combination of things- like crank oil seals as well.