For guys who aren't anxious to rebuild, the time to rebuild is when it's doing enough of something bad that you can't stand it anymore. Mine was burning a lot of oil but not smoking and had good compression. My starter caught funny and CLUNK! From then on a strange noise when running. Tracking the noise down I discovered the right end of the crank doing like a bent drill bit. So replacing the crank was my rebuild.
I thought it would be a shame to get that far in there without doing rings, esp. after finding good, cheap rings, so did that too. Interesting what I found in the engine. First thing I noticed was no obvious ridge in the cylinder, implying not a lot of wear. The gap of the top two rings were right in the middle of the spec., also implying little wear, but pressing against the wall weakly compared to the new rings I got. The gaps in the oil ring were very out of spec., implying ring wear since the other ring gaps were good. Because of all that and because I knew the engine had had lots of miles, but easy miles, I made very few measurements and didn't have any machine work done.
So you can spend a lot and make everything like new, or you can do what I did and basically fix what was broken and continue on. I had some head gasket leaking before the rebuild but was content to continue putting up with it, so didn't check for flatness. Fortunately it doesn't leak -- the new gasket fixed it.
BTW, I was around 60,000 mi. and have owned it since 17,000. Pamco Pete's ran to 80,000 I think he said. Bad crank killed mine, not sure what killed his.
) de-bur the seal bore...they sell a neat tool for that.. Mikes XS ?... a match'n socket to drive the seals home.. flush to engine case..
and meanwhile missing out on all that riding time
