When you ask for advice, you should take what is offered. A member of the WeFixit Yahoo group advised that I should clean the armatures with electric motor cleaner. As it turns out, I had some. I used it on all three of the armatures that I have handy.
The commutators had already been cleaned. I started with the dirtiest armature, the one from the hopeless motor. The stuff coming out of the motor as I sprayed that very volatile substance was really black. I sprayed until it came out clear. (I did this all OUTSIDE )
Next I sprayed the armature that came from the donor 15-91 . It was not as bad.
Then I pulled the motor from the 1936 201 and sprayed it. It was pretty clean. The brown glaze did not change at all. I am thinking it is supposed to be there. If not, well, I am not going to spend time scrubbing it off. I did try to rub it off with the clean rag I used to gently clean the rest of the armature and commutator, but nothing changed.
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