Hi jkeesey,
The OD-C3 (electric motor) is made of pot metal so I had a few problems with that issue. The field frame was broken in three parts, but Super Glue did the trick on that. The ground screw shaft was broken and gone, so I made a small sleeve to screw the ground into. The tip of the wiper shaft bearing cap was broken off, and neither JBWeld nor Super Glue worked so I fabricated a new bearing cap. The most time consuming has been the small brush spring retainer (there are 2 on the OD-C3). They were originally made of fiber but I have made a couple of replacements out of plastic. Problem is getting the right plastic so that the new part won 't break / split which has happened to me twice. I think I have the answer now.
I do agree with you that they can be rebuilt, and its fun to do so. A few of those small parts from suppliers would be a help too.
smurph