Motor slows down and stops
The motor gets hot and stops in a few seconds. The commutator has burn marks and beads of metal(?) alongside it. I have measured the resistances between each adjacent segment on the commutator, they are all between 3.5 and 4 ohm each. The brushes seem to be OK. Does the insulation break down? I tried cleaning it up but it goes bad the same way when turned on for a few seconds.