Rabco ST 4 motor question

I have just gotten a Rabco ST4 which I have gotten up and running, but the motor (which was in pieces when I got it, since it is only a press fit holding top and bottom together, and I guess someone had pushed on the pulley) vibrates the frame enough to be audible. It isn't obvious through the speakers, probably because of good isolation, but it can't be good. The motor uses a cylindrical magnet and there are many what I assume are poles aroung the perimeter, interleaved top and bottom. There is a capacitor involved, but the various connections seem to have been tampered with.
Does this sound like a mechanical or electrical problem?