My advice still stands. 26,000 miles is only the fifth valve clearance check for an airhead, and it shouldn't be loose by 2mm at all...ever. The valve clearances tighten up as the valves beat the seats into the head. Also, the cams lobes can't wear anywhere near that fast. They are harder than the shims. They can get scratched up by turning the cams over with a shim out of the bucket, but that's becasue of the higher surface pressure from the smaller contact area, and the sharp edge of the bucket lip.