03 Yz 125 top end problem

Blew my bike up then i got the cylinder nikielsealed , bought brand new piston and rings with gasket kit.

Put everything together to spec and started her up and she sound beautiful until a little rattling noise in top end area, after i would rev her up it would do it on the way back down. 

So i took her apart the cylinder is fine, but the top of the piston is &%$#@!ed along with the head.

What could this possibly be from?

the power valves look fine

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Your bike is detonating like hell! It needs a higher octane fuel for sure.

Your bike is detonating like hell! It needs a higher octane fuel for sure.


But what causes the rattling and all the notches ?

That's not detonation, you've got something bouncing around inside the engine. It's hard to tell but it looks to me like needle bearing pieces.

what jesel said.ur pics look EXACTLY the same as my top end did when i did exactly what u did(replaced it)only thing was the previous owner neglected to mention why the top end looked like it did and i didnt know enough to conclude there were bits of something rattling around the bottom coming up the to the top.so like you i changed the top end only to start it up and destroy a top end and cylinder.best fix is to split the cases and see whats in there,you could maybe get away with just taking the jug off ,take the motor out of the frame and flush it with compressed air.

Did you flush the exhaust pipe also pieces will stay in it also some guys rebuild their bike load it in a truck tips it back while loading puts stuff in topend

Thanks everyone, splitting case cleaning out and rebuilding again

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