All depends on clearance,over size valves will be closer to the piston when open thats why there are reliefs in the pistons for the BB kit. Not for larger valves but since the compression is higher the combustion chamber is smaller so the top of the piston is higher and the relief is so the valve doesn't hit the piston. Same thing if the dia. of the valve is larger then when open the lowest edge is closer to the piston and a stock piston may hit the valve. I have never done any measurements on these bikes in that respect so I don't know what the existing clearance is but that is very important to verify before doing that type of job or you could bend a valve or worse damage the head and or cams.

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