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2001 cr250 knocking.


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After hearing my other buddies new to him 01 cr250 I noticed how noisy mine was. Well I noticed a few weeks before, and started running a race blend to see if it was detonation, but the knock stayed. After hearing his run I decided it was worth tearing down. I put a new top end in the bike last year along with new crank seals and the top end looks good. The piston is light brown on top with a tiny bit of carbon buildup and there is no blow by at all. The cylinder looked fine except the piston skirt was rubbing against the bottom of the cylinder. You can lightly see the piston skirt outline on the cylinder wall. There is some light scratching. The wrist pin I can feel a groove that maybe is a .0005 or so with my fingernail. The lower rod bearing I can't decide if there is play or not.

What is a good way to tell if there is rod bearing play with the top end out? If anyone has any tips or has experienced this any help would be appreciated.

The knock seemed like it was coming from the top end, it sounded like a diesel kind of when it idled or like a valvetrain out of adjustment. Could that small wear on the wrist pin cause that? What would cause the piston skirt to run on the bottom of the cylinder? The new piston was an art 3s. I'm wondering if it could be timing also.. But I don't know if I should just replace the wrist pin and re ring it or just do the bottom end. From what I've read on hear some say the cr's are just loud but I think this is a bit abnormal. Thanks.

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my 02 is pretty noisy. you can check the connecting rod bearing by rotating it so it is straight up and down and tapping it with a soft hammer to hear a clunk or just grab it and see if you got up and down movement. side to side is ok. my cr as always been noisy ive read its normal and heard others that are the same.

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Detonation will typically only manifest itself when the engine is under a load, not at idle (unless you're seconds away from melting down).

I'd definitely be concerned about the groove in the wrist pin and the spot where the piston is rubbing the cylinder. Keep your ears tuned in to see if it gets worse--you won't want it to get much worse because you know what can happen.

I'd tear it all the way down the next chance I had and take the crank to a rebuilder to make sure it's true.

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