XR650L Clicking Noise in Top End

My 1998 XR650L with 30,500 miles on it is starting to make a strange noise. The motor is stock internally, and I have maintained it well with regular oil changes (Mobil1 red cap most recently, but I have always used synthetic oil since I got the bike at 12,000 miles) and filter changes and valve clearance checks.

The noise is a metallic click that ONLY happens when the motor is cold and at low RPMs. It seems to go away when I rev the motor up, but my bike is so loud I'm not certain of that. It is also irregular... ie: CLICK ... CLICK CLICK CLICK ... CLICK CLICK ... CLICK ......... CLICK ... CLICK CLICK CLICK CLICK ... etc. The engine continues to run fine (no missing) during the period when this CLICK noise happens.

Valve clearances are perfect and have stayed that way for the last five or six checks at 1500 mile intervals.

I have read about noises produced when the cam chain and/or tensioner is going bad, and also when the autodecompressor is going bad, but why would the noise only happen with a cold motor if it was those? If one of those were the problem I would actually expect it to be worse when the motor is hot... but I have no wierd noises when the motor is good and warm (250F oil temp, like right after pulling off the freeway). Just the normal air cooled thumper noises when it's warm.

I thought about piston slap, but the noise sounds like it's being made by a smaller part than the piston, and I would expect piston slap to be more regular than this noise is. Doesn't really sound like a wrist pin either, and again that kind of noise tends to be load-dependent instead of temperature dependent.

Any ideas what it could be? I used one of those stethoscopes we have in the shop to listen for the noise and it does sound like it's coming from the top end, right side, rear, but I'm not certain of that.

Thanks

Michael

I am not an expert but from what I have read on here and the word from my dealer is that it sounds like you may want to pop the top off and have a looksy...

I was told by dealer that clanging noise is cam chain..

I plan to pull mine apart at 30K just to see how its all holding together and probably do a top-end job just to be sure.

:cry:

I was told by dealer that clanging noise is cam chain..

It's definitely not a clanging noise or a grinding or dragging kind of noise. It's a CLICK. Except for it being irregular, it sounds like a misadjusted valve that is way loose. But the valve clearances are all OK.

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