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Need help please! piston hitting something!

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Alright I just put a frssh top end in the bike . I put all kibblewhite valves and springs, and a new headgasket in. Got it together and it wouldn't start. Pop started it and it ran fine. then at the track noticed that the piston was defianetely hitting something. All of my valves were in spec when I put it together last night.

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not saying that this is ur problem but I had mine apart putting in new valves and it sounded like a piston knoking but it was just my valves slapping the valve seal. What happens is when u break in ur engine your valves seat themselves in there really tight and then when u replace them they have to break themselves in again. If everything is still in your specs (vital) go out and start it and break it in again just like you would a new bike when ur finished, if all goes well it shouldn't be hitting anymore. NOT saying that this is ur problem but thats what happened to mine.

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Knock while it's running? If it's when you kick it over slowly it's the decomp clicking. Normal.

Or the timing is off or you didn't release the tension on the cam chain tensioner when you put it in.

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Check your timeing vavles and all that stuff. If its good just ride it and wait from something to break. It sounds to me that your just hearing what the 250 normally sounds like at idle. Does it make the same noise at higher rpms?

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If it won't idle and you hear a funny sound, sounds like your timing is OFF. The other thing you might check would be the decompression

release mechanism, it could be misadjusted and cause the bike to not idle.

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glad to hear u got it all fixed. the feeling of ur bike not running right or not running at all is horrible.

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the timing was off and the hitting was the decompression lever. It started first kick!

I see posts like this way too much. You should double check the timing before the valve cover goes on.

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Sadly I had this wonderful experiance. I had mistaked the Wiseco piston arrow for intake. Whoops! The piston went in backwards. The result. The valves lightly tapped the piston, it wouldn't idle for it's life, and i ended up buying a new piston bcuz the valves tore it up :thumbsup:

I will never ever do that again! :ride::cry:

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