Okay here goes, Numbers on the cylinders are 48H and Y-1, The head has the numbers 31K and Y-1. I used a caliper to measure the bore and got a reading of 64.5mm. Looks like the person before me did a little porting, In my opinion nothing serious, just a clean up job. I was going to port them and build a power valve motor and changed my mind, Jeff at F.A.S.T is porting my stock cylinders so I really have no need for these laying around my cluttered garage. Anymore questions feel free to ask. Thank you