Tonight I puttered in the garage tearing down the top end of the R50's engine. I took a few pictures mostly for future reference. I've found out that someone has had the top end apart before. The pistons are not original (they are the newer 3-ring type) and one of the rod bushings is a bit different than the other and likely a home-made item. The pistons look good and fit quite tightly so I may not need to bore the cylinders. The folks with the ultra-precision tools will be able to tell me for sure.
I tried to get the gear case cover off but it likes where it is now. I'll have to try heating the case to see if I can get it to let go.