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What does this sound like to yall?

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I have a yz250 2 stroke, I changed the top end about 6 months ago and ride about every week. Today at the track I heard a loud knocking noise, sounded like my piston was hitting/grinding on my cylinder. Yes I have collant in it. Is this from it over heating or what?

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I have a yz250 2 stroke, I changed the top end about 6 months ago and ride about every week. Today at the track I heard a loud knocking noise, sounded like my piston was hitting/grinding on my cylinder. Yes I have collant in it. Is this from it over heating or what?

 

 

Noises are impossible to diagnose over the internet, but knocking or grinding noises from an engine are certainly never good.

 

You aren't going to know without pulling the top-end off.

 

DON'T keep riding it, you'll do more damage than has already been done.

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Yeah its hard to explain how it sounded, imagine hearing the piston hitting the top of the cylinder each time it went up. I'm gonna tear everything down and see whats up

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Piston slap?

 

 

Piston slap isn't loud, and it doesn't sound like grinding. It also usually goes away under a load, because the combustion pressures tend to force the piston against the exhaust side of the cylinder as the rod passes TDC.

 

Piston slap is also much more prominent with a cold engine.

Yeah its hard to explain how it sounded, imagine hearing the piston hitting the top of the cylinder each time it went up. I'm gonna tear everything down and see whats up

 

 

If the rod bearing or wrist pin bearing gets sloppy, the piston can actually contact the head.

 

Time for a tear-down.

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Sound like the big end going/gone. I would definitely find the problem before riding it. If something lets go, the bill could triple.

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