RM 125 Piston Question

I live in So Cal. The dealers don't stock parts here, less maybe Chapparal. But they can "get them for you in a couple of days"....UGH. On top of that, your basic parts guy couldn't tell you a 125 piston from a 450 piston let alone something like this. But hey....... he has a bunch of cool tats, black socks and a sideways hat. Every time I go to the dealer I tell myself that there is no way that they couldn't have this part. Every time I leave shaking my head as to why they don't have the part.

Because I have an 02 that has a poorly shifting gear box. I was going to buy a 04 cases gears etc. and bottom end on the cheap but noticed that crank and cylinder /piston were different. What I have been able to learn is that all years from 01 to 06 less 03 have interchangeable gear boxes and cylinders. 04 on he crank is different (longer rod) and each year has different cylinders but thet are interchangeable. Also from what I learned the 04 on have a flat top piston. I figure that I will buy the crankcase put in my low hours 02 crank and just make sure that I degree the motor out and check the squish when I rebuild it.

99% of the time, I would agree with you but, the bike has a ton of hours on it and has multiple bad parts. Trust me I would rather just drop in a new shift fork but 2nd 3rd and 4th are heavily worn. Add to that, all of the bearings should be replaced and the drum is suspect. This was a project bike that was obviously used and abused. Since I can get this low hour 04 bottom end for $100, it seems worth it to do this.