My trusty 2008 XTR . Been running it for 2 trouble-free years now as a go to work hack. It gets used fairly hard as we have lots of open roads around here. It regularly has a sprint to over 100 and I usually sit at 80 to 85mph on my 15 mile commute.
Last week I glanced at the clock as I slowed down from speed to see the red temperature light was on, and tick over was very fast. After stopping I found the hose from thermostat had come off due to a loose jubilee clip. I don't know how long it had run without water . I replaced hose and all seemed well for the rest of the week. At the weekend I fitted a k&n panel filter and removed the snorkel, I was so pleased with the way it went (especially with my loud Arrow cans) I even polished the bike!*
Slowing down last night from an indicated 100 it sounded odd on the over-run, kinda vibey too. It now seems very noisy and vibes can be felt through bars, pegs and seat. The only time it's quiet is when it's hard under power. I'm struggling to pinpoint noise but I'm starting to suspect big end bearing is going. Perhaps I've been too hard on it. Is the motor worth stripping as it's only done 16500 miles and most second hand engines seem to have covered more?

Had the same symptoms on my previous bike, the problem was unscrewed bolt fixating engine on chasis, so i would check all of those 1st

I think I now know what the noise is. I reckon it's primary drive nut on end of crank is loose. Seems that it's not unheard of.....