Alright. enough debate. Here is what I know about the pistons and cylinder business. All mojor bike manufacturers use some sort of labeling system for new parts (this labeling system refers to NEW PARTS ONLY!!!!!!!). Honda uses A, B, and C for their pistons and cylinders. The difference between the parts is a mere.0010 or .0015" between the three. Honda uses very tight tolerances when building parts and when they run off a batch of parts, tool wear is taken into account for the fitment of pistons and cylinders. For example if you are boring 100 cylinders at a time the first cylinder is going to have a slightly larger bore than the 100th cylinder due simply to tool wear. To save time and money on tooling honda simply has 3 different pistons that take into account for the wear on their tooliing. It is a very simple concept. If you look in the pilot manual the tolerances for a stock piston are tight at .0031 inches of piston to cylinder clearance. (this is the difference between the size of the bore and the size of the piston. Meaning that if a cylinder measured 3.1750 inches in order to get the proper tolerances the piston would have to measure 3.1729" inches.) As I understand it the C piston is the smallest available, so it will in fact fit into a B cylinder, but the tolerances will be loose for a NEW piston and Cylinder combination. Monkey wrench never did get that right with an order i placed with him one time. After the first piston has been run through a "lettered cylinder" the lettering system should go out the door period. Any cylinder that has been bored or honed should have the tolerances measured by someone who knows what they are doing, and the cylinder fit to the piston. Using this, the most desireable cylinder would be the "C" cylinder and with wear you could hone the cylinder to the next letter honda piston when needed, taking into account cylinder wear. If you do it this way you can get a lot more uses out of a new cylinder.
If you don't get any of this, all the lettering system is used for is for NEW PARTS. That is when the letters need to match, but do not necessarily have to match. Like I said above any letter piston CAN be run in ANY letter cylinder. It is just a matter of tolerances. You would have to hone a "C" cylinder to accept an "A" piston or you would have to live with a little more piston to cylinder clearance running a "C" piston in an "A" cylinder.
If this isn't clear to anyone let me know and I'll see if I can explain it more clearly.
<EDIT>
Post is fixed...C is the smallest, cylinder and piston combination. And hence the most desired. You could start with a C and C combo then hone out to a B piston, then an A piston, then your first oversize, at whicj point all letters are thrown out the window and mean nothing.
