The owner's manual should have the info or there might be an info label on the motorcycle somewhere under the seat or behind a side cover. I didn't see the fuel octane info in the 83-85 1100 manual.
From the 1981 KZ650-CSR owner's manual: it says to use 87 [(R+M)/2] or 91 [RON] >>> or a higher octane with either method.
The pumps around here are labeled [(R+M)/2] and ethanol-free isn't available.
Most of the time I use at least 89 octane, but I kind of alternate between 87, 89, 91 & 93.
1981 KZ650-CSR. Competition, Sports & Road.