I'm there with you, check my build thread. The ring size depends on the piston size. Piston/ring size depends on how much meat you have to take off the cylinder walls(boring) to clean up scratches and/or return the whole thing to the same dimensions from the top to the bottom of the sleeve. If there's next to no scratches and the dimensions are uniform top, middle, and bottom, a good honing may be all that's required(for the cylinders-put in new rings regardless). If that's the case, AND there is no damage to the stock piston( measurements and tolerances can be found in the manual downloadable on this site) STANDARD ring sets are needed. If the piston is damaged, STANDARD pistons and ring sets. If the cylinder needs to be bored, it can be bored one quarter of a millimeter bigger in 4 increments, up to one mm larger TOTAL, then it's time for new ones. There are piston and ring sets for each of these overbored sizes(.25, .5, .75, and 1.) A very wise man from the SOHC4.net website named Two-Tired taught me that Honda carb parts are available and worth the money so you don't have to guess whether they're good or not. Your call, though.