Yeah, i measured the piston, and it is NOT a 42 mm. I think that andy;s is selling this kit, but it really isnt a 65cc kit. In fact, the old and new cylander look alike, except for the fact that the new one has a bigger intake port. I think there should be SOME improvement with a motor 15 cc's bigger, and you should notice this power immediately.
On my puch, when I installed the 70 cc kit, I barely touched the thottle and had SO much more power. ON the avanti, there should be some notice of power, but it feels slower than before.