What comes apart when RPMs go too high?

I have only had my '82 KZ650 CSR H2 for a couple of months, and plan on leaving it completely stock. The engine runs great and revs very easily, so I am very careful to keep the RPMs from going anywhere near the red line on the tach, which is at 9,500. I have read that these engines are very durable, but being a curious, engineering type guy, I wonder just what finally does let go in these engines when they are over revved.

Sorry to be so morbid, but I wonder what the weak link is, that finally does come apart and at approximately what RPM. Surely some of you high performance owners can answer this. Thanks.

The first thing that'll happen is the valve springs will lose control of the valves. Usually referred to as valve float.
You will probably be safe 'til about 10.5-11k though.

Little brother's 82 GPZ-550 lasted one summer with repeated runs to and beyond redline, the rod bearings finally let go and messed up the crank. No undersized bearings for it (hardened journals?) so he sold it for parts.