Piston markings....

Soo...here's a little backstory. I installed new valves (Kibblewhite Black Diamond) and I had new intake valve seats installed, and the exhaust valve seats were cut. I reassembled everything last week and heard this sound coming from the engine. (listend around 43 seconds or so..)




So I tore everything back down and am doing some inspection. Below are my findings.






Im trying to remember if those two little circles on the piston (where the exhaust valve notches are) were there prior to the new install (I think they were). Is that normal? IT looks to me that they may be the center mechanism for the boring tool when they notch the piston from the factory. The only way the valve could make that mark is if it was completely flattened. The valves are coated in black, and none of the valves look like they have come in contact with the piston, as the black coating is still intact.


I've inspected everything else I can think of and can't figure out what caused that noise. Any suggestions are helpful and appreciated.

Edited by RAGEman

Swirls are from the machining of the piston. Not from valves. The stainles valves are a tsd bit more noisy at certain rpm. Usually once you get on it-its not noticeable. I only put ss valves in a crf450-not sure what they sound like in a 250f. Msybe someone else will chime in.

Hmm can't say I've noticed any difference in engine noise with ss, sorry

 To me it sounded like something in the timing chain. When you reasemble it make sure the tentioner is installed correctly . I installed mine upside down once and it made a simular noise.

I bought a new timing chain, so it should be here by the weekend. I double checked, and I did install the tensioner correctly, but while I'm in there, i figured I might as well swap the chain. (only $34).


This may sound like a stupid question, and I know that I already know the answer, but I'm grasping for straws here...Is it possible that while I had the head off that one of the piston rings may have slipped past the base of the cylinder and came out? Surely not....right? It wouldn't run like it did...? I'm considering replacing the rings while I'm here....I don't know what else to do...

Edited by RAGEman

Doubt the ring slipped. I have seen them stick or installed wrong..usually it will jist have poor compression,power or smoke. Id make sure timing,bolt torque,tensioner and cam chai guides are all good. If you doubt it that bad and concerned-take to a shop. Probably wouldnt cost that much for 2nd opinion. Or..hit up a buddy that can give opinion...if he is knowledgeable about the bike.

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