Long overdue update, the motor had a tight spot which I've never found the cause of. This winter will be time to open it back up.
The Hayabusa starter was probably not the best choice but at least the gear mismatch didn't make shrapnel. Mine may need a rebuild, it doesn't seem to be an improvement.
I was looking back through the cb900 / 1100 info. The starter that seems to be the one is Mitsuba 31200-438-018 .800kw and SM220 on the end casting, for cb900c through 1100f it appears to be 80 through 83.
I haven't found any info the newer starters fit early bikes but they are way cheaper used.