Two Stroke Piston




Could anybody tell me what the marks on my piston and cylinder head are from? Also if it is running a little to rich? I'm assuming the marks are from sand getting sucked through the intake somehow or something because there are no marks below the rings. The piston has about 25hrs. on it, driven lightly through trails. I took the jug off because of piston slap, cylinder needs replating, as the exhaust side is worn straight through the nikasil.



Edited by cale8220

Forgot to mention, the brown on the head is mostly just oil caught in the small nicks

That is from  aluminum from the piston vaporizing and  exploding 

Edited by KRANNIE

I think I would replace the ignition side crank seal just in case it's leaking causing a lean condition.

I changed both crank seals. Could this be from to advanced timing? I got the bike from a previous owner who changed the stator, but there are no timing marks, and I have a feeling that it is to advanced. It is difficult to start, requiring a few hard kicks from standing position regardless of whether I it is hot or cold. The jetting is currently stock and I have a FMF fatty, and boyesen reeds.

Edit: Recently changed both seals because the right one was leaking. I guess it wouldn't be to difficult to change it again.

Edited by cale8220

Too advanced of timing will cause detonation and can show marks on the piston.


Took the piston off and It has definitely been overheating, would detonation cause the oil to burn on the bottom of the piston as well? Or is this simply because of a lean condition?

Edited by cale8220

I guess detonation could occur because of a lean condition. Might change the crank seal and have a mechanic time it because i don't have a timing gun or the know how for timing an engine without marks on the stator plate. Is there anything else that could be possibly causing this that I should look into?

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