TNC - I'm not convinced that the idle noise and the at-speed noise are really the same. I originally assumed they were, but now it seems less likely. The bike is wonderfully quiet at light to moderate throttle at all rpm.

I've followed Krieger's instructions on the tensioner, have heard the noise made when it's too loose, and heard it go away when finger tightening - so I'm fairly certain that's not it. I've readjusted the tensioner multiple times at this point, including trying it as tight as I could with fingers and *not* backing off a flat, and none of that has had any impact on the noise in question.

Would the noise occurring only under fairly heavy throttle be symptomatic of the cam chain? Is the cam chain noise usually very consistent or is more random and rattly? My noise is extremely consistent and rhythmic.

I'm anxious to see what I can see with the drive chain at lunch... at least it's something new to try! Thanks y'all.

 

Yeah, it sounds like you've pretty well addressed the possibility of cam chain tension. And cam chain slack is not usually consistent like you're describing. It tends to be more cyclic at certain points in the rpm range. I still wonder why you have a very noticeable noise at idle even if it's something different. Checking the 15T sprocket contact possibility is a good idea.

 

No luck on drive chain. Removed guarding and tightened to the tight side and no change.

The bad news is I spent some more time with the stethoscope and I'm now thinking bottom end. Idle noise seems loudest when probing at the water pump cover. Marvelous.

I seem to remember reading about someone with a noisy water pump, and another with a balance shaft bearing going out? Any thoughts on how to tackle this?

Was really hoping this wasn't going to be this difficult, but I've about run out of simple things to look for.

 

Sorry to keep crapflooding the board...

More stethoscope probing over lunch led me to this - the gear in the picture has a good deal of play in it and goes "clack clack" when I push it back and forth. Which reminds me that the starter goes "clack clack" when the engine is just firing up.... loudly.

Hmmm. Didn't have time to dig further than this, but I guess I might be pulling the clutch cover off this evening to investigate.

*Edit* On second thought, maybe I'll pull the generator cover off instead, seeing as how the clutch is on the other side.

 

I'm vague here, as I haven't worked on this aspect of my KLX, but isn't that gear supposed to do that? I know this...dan888 should be a wealth of info on this specific issue due to his recent situation with his bike.