650/750/750 twin/900/1000 use the same sprocket pattern, so does ZX12
Not sure what others will fit.
Save yourself some time and money, go to JT Sprockets (Every time I type that I think of the Jetsons) and look up the sprocket for your bike. Take note of the dimensions listed for the rear sprocket, take those dimensions and compare them to other bikes on the same website.
To save time, just look up the rear sprocket for a 1980 KZ650 and search using the first part of the part number.
I just happen to know that it is JTR488 because it also fits a 750 twin. A search using that part number will show you a list of every bike that uses the same bolt pattern and 530 pitch.
I've already done that, and no bike using that bolt pattern has less than 38 teeth.
I have a ZX12 LSR bike, and the ZX12 comes stock with 45 tooth rear, but I need sprockets with a lot fewer teeth to make the bike go faster (it has enough hp). And KZ650 rear sprockets are a crap load cheaper than ZX12 rear sprockets, even though they are the same, so I shopped eBay for cheap 650 sprockets.
Thanks to JT sprockets allowing me to see what will work.