Did that. First, I thought about it being the sidestand and put a small rubber pad where it rests so it can't be making the clack. I really don't think it's the center stand hitting the stop. The stop has a rubber bumper plus I rode the whole trip with it ZIP TIED tightly in the up position (which keeps the legs from moving but I do think it can still move at the pivot since my zip tye was down where it hits the stop). It's distinctly a metal on metal sound. I thought about it being the chain too. I tried hitting stuff both hard on the gas and hard on decel hoping that with the chain taught on one run or the other I'd find out which side was slapping, but it didn't seem to affect the sound one bit. I remember my old YZ426F made all kinds of racket with the chain hitting the slider and I put some thin foam under the slider which helped a lot.