I have 1 50 with the black top with the 45mm used cylinder but still has 45 stamped on top it has no transfer, lines, gouges, damage of any kind. I bought a oem 45mm piston, ring, bearing, and pin. Rebuilt the walbro carb and put new lines and filters on it. Everything works as it should. Excellent compression and runs like a beast.
I also have another 50 series that I had to use a 51 top and a 51 starter assembly I still have the black top and 50 series starter assembly, I just couldn't locate the 50 air filter to choke it. I currently have the Zama with the choke lever but I do have the walbro 50 series carb and bulkhead just no air filter to choke it with the trigger on the 50 top cover. On this 50 I have a 46mm oem piston in just the same if not better cylinder still stamped clean and no transfer, lines, gouges, or any damages. Bought a oem piston, ring, needle bearing, and pin. New lines filters and carburetor kits on both. Has a 20" bar and chain on this one I have a Oregon lightweight for the other both ⅜ pitch. Both run excellent and are ready for work. 828-205-1166