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Strange noise in topend 2006 kx450f

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So my son got a new bike and when he got it home he started it and ran fine except when he revs it, it makes a noise when the rpms fall back down. I was thinking the timing chain or guides were bad, so we opened it up to put the new chain and guides in. When I dropped the oil there were a few copper flakes on the drain plug. At this point we removed the cams and the exhaust cam bearing seems to have some slop in it, so he ordered new cams for it.

I'm just wondering if the cam bearing would make a noise like that or if I'm on the wrong path here. Any opinions would be appreciated.

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brass flakes are usually from the crank bearing cages.....time for a new crank

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brass flakes are usually from the crank bearing cages.....time for a new crank

Yeah I've read that many times on here. There was only like 5 little flakes on the drain plug so it must be just starting to wear. Are brass flakes always just the big end bearing or is there any other places they could come from?

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There may be a few other bearings in the trans that have brass retainers on them, but since youre hearing noise im guessing thats the worn out bearing you ar hearing.

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I'm sure you are correct. I have a feeling the noise I'm hearing is unrelated to the crank bearing because it sure sounds like its coming from right up top, but I've been known to be wrong before lol.

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Ok, well the brass isn't coming from up top. Is your valve lash in spec? What bike did you have before? If it was a 2 stroke, then you aren't used to hearing normal valve train noise.

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I have an 06 kx450f and the bike I'm having problems with is my sons which is the same model. Yeah valves are in spec. I talked it over with him and we are just gonna get a new crank and piston just to be safe. Crazy thing is I've known this bike for 3 years, it was a good friend of mine who owned it. It had been a great bike but that's just our luck I guess lol

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'06's had wrist pin problems i think. I would check your valve lash before you go an tear into the bottom end.

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Be sure to check the cam chain tensioner too.

Yeah I already replaced that along with new guides and timing chain and that noise was still there. He wanted stage 2 cams anyways so those are coming. We plan on pulling the head and cylinder now to check the crank and piston now.

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Well not too much info to report but we rebuilt the bottom end and did the piston , cams, timing chain and guides. Noise is gone all good now. I'm pretty sure it was the exhaust cam bearing but we did it all to be safe.

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