Normal. Only thing you can do to lessen the noise is to make sure your idle is in the 900 to 1000rpm range and make sure carbs are synced and overall in good tune to make the engine itself run smoothly. You can rebuild the clutch but the noise will return again. Other thing is to make sure you are actually hearing clutch rattle and not cam chain noise...remember you have to chains that need periodic adjustment on the dohc motors.