I took apart my two Cl175 motors (one ran but smoked a ton and fouled the right plug, and the other motor was a spare), and one has what I think are standard pistons, and the other has larger pistons. Both say HONDA. The smaller pistons have the numbers 313 and 3 and the larger pistons say 313 7. Does this denote the oversize? I need rings for one of the larger pistons(oil ring was missing a chunk that I found in the bottom of the engine). The good news is that the bore wasn't harmed and still shows a nice crosshatch from the rebuild. The bad news is that I took a piston from the other motor and installed it in this motor, which is now in the bike, before I realized they were different sizes. Luckily I found out before I completely installed the motor and ran it (I only ran it for about a second on the bench). At least I'm getting my mistakes out of the way on these little motors before I attempt the big bore and rebuild of my Cb750. Jimmy