I have heard of people using brass or plastic tubing to fix the issue, but brass will cause shorting in the Bachmann split frames. I do have a Lionel (made by Bachmann) branded GS-4 that has the same issue. I'll be working on it in the fall. Super Glue only worked once around, then no more.
I am looking for a repowering kit to get rid of the sorry little "pancake motor"