XL 2 is 1-5/16 bore. Super 2 is 1- 7/16 bore. Both are 1- 3/16 stroke. Both have HDC carb on the bottom of the crankcase. XL2 is 26.2 cc. Super 2 is31.2 cc. Take the muffler off. Stick a popsicle stick through the port to the other side of the cyl. Push the piston against the stick so the ex port puts a mark on it. Measure the stick from end to mark to find the bore size. Hope this helps.