my os 77 on the dynomax will spin 22,500 with a custom con rod
You can't turn much rpm for very long with the stock rod in a .77. I have bent a couple of them in Byron fans that don't turn as many rpm as they do in the Dynamax.
Another trick with the OS.77 is that you can run a back plate and carb from an OS.91VRDF on the .77. Works very well!!!