I find the rotor has 48 conductive bars. I could have this wrong.

By substituting the rotor, could I increase the efficiency of this
motor? That might be much easier than rewinding. I have removed and
replaced rotors from shafts before. It seems any rotor with the right
number of bars and less than or equal to the linear size, with the
right or smaller bore, would do to make *some* improvement. I'm
guessing I'd want a rotor with fewer bars, but I don't know the
physics.

Can any reader show me the math relating 60Hz, 36 poles, 400 rpm, 48
bars, and 225 rpm?

I don't get it. I take 7200 / 32 = 225. To get it, I need to go to
Falls Church's library, the Mary Riley Stiles library. There are not
one but two editions of Audel's there.

Doug