I have recently purchased a 2008 model and have noticed a "noise", quite distinct, coming from the running gear/primary drive sprocket area. It is not an engine noise, if I cut the engine and let the bike roll it is quite still noticeable with or without the clutch engaged. It doesn't sound like a bearing rumble, more of a higher pitched "rattle". Is it a problem?

 

I have very little experience in that area BUT the first thing I'd be doing is checking everything in that area to make sure there is nothing working it's way loose! Rattles never "fix" themselves! lol

 

Like @Doc Samson said, they rarely fix themselves. Sounds like you've narrowed it down to chain and sprockets. A place to start anyway.