(ET) E20 motor teardown to find the ground fault (opinions needed)

[Chris Zach <cz alembic crystel com>]

Ok, so I figured the motor was not going to fix itself and took it apart 
today. Removed the huge front pulley with my 3 fingered pulley puller, 
then pressed out the armature and set it next to the E15 armature.

Note: It's a bigger armature, no doubt.

I then unscrewed the field screws on the motor (hint: Find the *exact* 
size screwdriver, clean the slots of all crud that might keep the 
screwdriver from fully engaging, put penetrating oil in, and use a 
wrench on it while putting pressure down with your shoulder. These heads 
could strip) and started thinking about how to get the field wires out 
of the plastic housing (so I could thread them into the motor and pull 
the windings out) when I figured I should test the motor again with my 
sparker.

No spark at all, no ground fault. Hm.

Put the screws in on one field side: No ground fault. Did the other, 
ground fault.

So it looks like the fault is between one of the field halves and the 
motor body. If the screws were not ferrous that could fix the fault but 
I don't know if nylon screws are made that big and if they would hold 
under the motor's heat range. Debating if it's worth it to pull out the 
field, I could wind up breaking more of the insulation and making it 
worse. I know that the short is to the metal field support and not to 
the motor body because it will spark on the inside of the motor on the 
side that's shorted.

I might be stuck here running with a ground faulted motor, or I could 
bypass the whole compensating field and just run with the series one. 
Which would be a better option?