steve, this question is mostly for you but I made it a thread because I am wondering if any other riders have encountered this problem. I just got my bike back from the shop after my friend knocked it over and they replaced the clutch cover, brake pedal, and throttle. It seems to run fine (I am always parinoid something is ready to break though) but in between 4 and 4.5k it makes a very strange rattling noise it comes on and then disappears. At first I thought it was the chain but then I heard it while the bike was idling high with the choke on so I ruled that out. I hypothized that it is a braket or fitting that is lose somewhere and is reaching the proper harmonic level to vibrate. I am not sure though. Any ideas? Could this be something terribly catostrophic? I am debating taking it back to the shop that worked on my bike and giving them a hard time but I do not want to be an ass if I do not have to.