If it is in fact a valve hitting a piston better not run it anymore and hope you haven't bent it. I was thinking easiest first. With any luck maybe just check the cam timing and could be off thus causing the valve to hit. If not then it's a much bigger problem. Have you done over size valves? Not sure how the Wiseco pistons are cut but it isn't possible a piston is in backwards, is it? On the old bikes one valve cut was smaller than the other and had to go in the right way I would imagine the same is true on these.

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