i kinda think it depends on what you want to do with it. if youre going to ride it, bore it with the biggest pistons you can get from honda. dont bother just going .025 over. (go 1mm over) you can still get em from honda, or watch ebay. i buy all my pistons on ebay. rings too. waay cheaper than honda. pistons will run you 60 each and rings will run you about 20 each from the dealer. you can buy the whole kit for about or less than 100 bucks on ebay. the cyls are easy to get, so dont worry about going too big. jugs are a dime a dozen. a standard valve job should do wonders. get a radiused type if you can find someone to do it. new springs, help usually. but you can check them to be sure they are in spec. (the book will cover it). if youre going to race...depends on what class and which club. you can go crazy and spend thousands on a race motor easily. the bottom ends hardly ever fail. get a slipper type chain tensioner.
jc