RE: Can anyone ID this?
No, it's not a Cub, I have an A and B model and owned acouple more over the years. This thing has a brass crankcase, brass cylinder with steel liner, and two holes at 180 degrees for mounting. I have a feeling it is a home engine builder's special, maybe using other internals, maybe not. It has not been removed or disassembled yet, so internal details have to wait.
MJD