Ok, so my new-to-me '93 XR650L has 7500 miles on it. When I start to roll on 2nd gear at low revs, I can hear the cam chain doing its "clunk-clunk" or "knock-knock" (different noise for different boys) under load. So, my question is, how bad is this? Does it happen to everyone at low revs in any gear above 1st? Do I need to fix it, or is it normal and ok. It only happens when I stress the engine on trails and lug it in 2nd and up.