Alright so I just purchase a new 675 and only have 500 mile on it. At 300 mile I made a slight chain adjustment, and started to notice a slight vibration and fairly noticeable (wife noticed it while on the back) noise coming from the rear end. The noise and vibration sound/feel very similar to new brakes before they are broken in. First thought was to tight/out of alignment chain. Doubled check everything and everything was spot on. Next I loosened the chain to max spec, and the noise/vibration is less but still there. Next pulled off the caliper and went for a ride, and to my disappointment the noise didn't change at all. Just now I pulled the rear tire to check the bearings and everything appears to be in good order. After putting it back together the problem is still there. My last guess is the counter shaft (which I am preying that it isn't ). It only does it between 18-21 MPH, and completely disappears at all other speeds. Has anyone else had this problem, or what could be the possible causes? I have been riding/working on bikes for many years and never ran across anything quite like this.