On a 1985 K100RS, I know it's 23 years old and rubber pieces and nuts/bolts need refreshing. The bike runs well, besides a high idle that I'm going to leave alone. I replaced the handle bar rubber and ended up stripping the thread on the mount (a set os bought off ebay). Replaced missing bolts on the heat shield and now it rattles like crazy whereas before it didn't make a noise even with missing bolts.
I think I just need to leave well enough alone. Do the services at regular intervals and repair problems instead of creating them.