The battery acid part jives with what MCRider has been saying for a while now. I didn't really believe it, but I do now!!
Yay! I knew I'd seen that in print somewhere in my earlier days, But i could not for the life of me find it. I think I always searched under CB750 Service bulletins, forgetting that it was a generic all-bike bulletin. No other reason ever fixed the problem or logically made sense as to why it was happening.
Note the date 1973. That's about when the CB750 breaking mysteriously stopped. Attention to routing of the battery tube is crucial. Especially when the bike is put on the side stand. The angle allows an out of position/ too short tube to drip right on the chaiin.
The tube should pass down the right side of centerstand mount, I tie wrap mine to the mount, and be long enough and low enough that it can't drip on the chain under any circumstance.
Many of the major chain manufacturers have the same warning in their install documents.
Thanks CycleRanger for confirming I'm not crazy.