this may be a silly question, and I am sure you checked, but are you picking the brake in the down direction. Also if the commutator looks like a new penny, let it run a while and get a glaze built up. Empty car up the counter weights are helping you, empty down you are picking a load. I would get the motor shop to get someone on site to make sure the Genny fields are wired properly.Don't discount the Motor fields, you may still have an issue there.
