Maybe just lucky but I have multiple 750's that have never been opened up still getting on down the road.
I, too, have been impressed by the internal condition of so many of the engines I have opened up in the last 15 years or so. The ones that have worn/chunked/hardened cam chain tensioner parts were also those that had incorrect oils run in them, judging by the general condition of things like their clutch discs, main bearing wear rates and primary chain wear. Once the cam chain roller gets chunked up, the cam chain suffers more wear from vibration shaking the oil out of its links while bumping over those irregular surfaces. When the clutch is in fine shape, the main bearings barely worn, the cam lobes happy and young-looking, the rubber parts in the cam chain system are also supple and not rock-hard, despite the mileage. The most impressive one I've ever seen was a 58k mile K2 engine that had always had Amsoil in it, 20w50 weight, from Wyoming (2011). The owner had removed the #2 exhaust pipe (for repair) and the shed where the bike was kept lost a wall panel in a windstorm, away from the house where the owner didn't see it. The exhaust port got packed with snow. The next Spring the owner discovered the engine was locked: that cylinder had rust enough to stop it, so he sent it to me for general rebuild. While a light honing would have sufficed, it was fully bored to oversize and sent back for what I am sure is a very happy life, still.
