I don't suppose you have a photo? I haven't touch an Entour in a long time, but it sounds like you are along the right lines, they have 2 little grub screws onto the spindle of the stepper motor. These do have a tendency to be a PITA to remove as they start corroding at the slightest hint of moisture!
As said above, sounds like it could be a stepper motor driver chip. They can be tested on the older Mac 250s etc. with a Martin stepper motor driver tester but I'm not sure if that works with the Rush stuff! I would carefully check the loom first though, just in case... it may have been rubbing somewhere!
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