What happened to this 365sp?

[Northerner]

Tell me what you think, lean? Overheat? Straight gas? Intake side is good.
I have a pretty good idea but will save it for later.

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[Fatherwheels]

Lean me thinks, but are there little round marks on the cylinder, did it ingest something

 

[Woodslasher]

Looking at how the piston is I'm gonna say carbon and/or blowby was a contributing factor.

 

[TLG]

Curious what all that crap ia around the plug hole and combustion chamber. Nickel anti seize??;There is a ton of it. If that's the case that would of started issues on the exhaust side.

 

[Clyde85]

I was thinking that was aluminum around the plug hole.

 

[Lanedrew]

That p/c definitely got hot, I’d say straight gassed or major air leak maybe a crankseal, or maybe even just over revved for way too long

 

[Northerner]

Well here’s the deal. Typical homeowner, “needs a tune up or spark plug”.
Saw had low comp, did leak/vac test before taking apart. Had very small leakage, and that I narrowed down to decomp button.

Took it apart and saw the damage. Checked back with owner and asked if saw had been straight gassed ever. Umm, yes once about a year ago. So they ran it till it was done.
Plus I still found the inside very dry, so iam gonna see what kinda mix he’s running. One more thing, piece of the case is knocked out that surrounds flywheel, about half the air goes out there instead of over the engine.

So I think it was a combo of things, damaged with straight gas, over heat, possible a bad mix yet too.


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[Northerner]

The ring was also noticeable thinner on the exhaust/damaged side. But I assume that happened after the damage was done.


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[huskihl]

Straight gas usually scores all the way around the piston. Looks like it was run lean. Could have been tuned too lean or possibly a bad fuel line or fuel filter. Or stiff diaphragms in the carburetor