Induction motors do not have magnets in them, instead the magnetic field the outer coils generate creates electricity, and subsequently magnetic field, in the inner coil. This means those motors need no brushes as the inner coil is not connected to anything.
I was wondering, purely academically, if you could prime the motor with field first, by putting current through the outer coil and then spin it to generate electricity. Assuming you'd spin it correctly, I imagine the magnetic fields would maintain themselves using power absorbed from the motion until the system came to a halt.
Is this possible or nonsense?