If your 8200 runs, cuts, and idles like it is supposed to, what is the problem? I would not tear into that thing if it is working properly. There are several parts on those that are not easy to find. The piston is the hardest to come by, and it is not quite as easy to change as others, due to having to press the needle bearings into the piston. It would be very easy to create an air leak on that one since it is a clamshell engine. Air leak = junk unobtanium piston. I would just run it and have fun if it were me.
I appreciate your comments. I didn't know what a clamshell engine was until today. I'll be careful if I tear it down to replace the rings. The reason I bought this size of a saw is to fell large oaks - I get my firewood from dying oaks that are usually 24" or greater at the base. I usually use a ProMac 700 with a 28" bar. Occasionally I wish I had a saw with more power. Once the tree is down, I usually buck it with a Stihl 036 Pro with a 25" bar. I also always have a back up saw when felling large trees. I don't like walking behind a tree as I fell it; sometimes the Stihl is too short (and not strong enough to pull the next size bar). I have always been led to believe that the 5.0 cubic inch Mac's were hotrods compared to the 4.3 cubic inch Mac's. I just want to get the potential out of the 8200 and since the post office lost a few critical pieces I didn't want to spend money replacing everything just to have a mediocre old saw.