This is a real mystery. I went out and looked at my green 77 KZ650B and it is notched, however that cover was replaced with NOS Kawasaki about 15 yrs ago. Thinking maybe the replacement was not identical to the original, I found my original green right side cover and it is indeed notched also. I looked through every cover on every KZ650 I have sitting around and all of my Bs are notched. I don't have a C sidecover to compare, but going by your pictures I'm sure I'm getting the right idea of what a notch is, but to be sure I plugged a green 77B right side cover onto a 1978 KZ650C with a master cylinder and it was indeed notched and fit. I'm sorry, don't get it as all mine are notched. Good luck to you.
321,000 miles on KZ's that I can remember. Not going to see any more.
