I think Pamco Pete said he ran one to close to 100k without tearing it down. Mine came apart at 68k to replace a separating crankshaft, not a common problem but not unheard of either I gather. At 68k there was no cylinder wear to speak of. The two upper ring gaps were in spec. The two oil ring gaps were very out of spec although the bike wasn't smoking. The valves and seats were ok. The stem seals on the intake side looked okay, on the exhaust side they were disintegrated. I put in a crank, rings, and stem seals. A couple of the places I was looking for a crank at were surprised it hadn't made 100k. I think if it hadn't been for the crank it would have made it easily.
Also, you will like to hear that by the time it needs something big, you will have so much experience with it that you will actually enjoy getting into it further. Probably no more information out there about how to do it on any bike as there is on this one. You don't need a lot of things like you see in pictures here, nice engine stands and work benches. I did mine outside on a patio using a free pallet as a combination engine stand and seat. Much worse than when a member came over once and I was sitting cross-legged in a driveway working on carbs. He was pretty sure I needed a clean room and surgical gown. I use mostly Pennzoil 20w50 on the recommendation of Pete, although he doesn't use it anymore. They supposedly removed some of what one beloved member referred to as "zink". But Pennzoil assures us there is still more than enough zink. If you want extra zink I read STP oil treatment is chock full of zink.
P.S. One thing I forgot was the front cam chain guide rubber was completely off. I think it had just happened. There was no big noise from it but I was noticing if the bike was on the side stand there was a slight whine, but not if upright. Much less dramatic than I would have expected! I guess the chain was rubbing against the side of the guide funny when it wasn't upright and that was making the noise.
