All:
Based on everybody's work here, and my own experience, I would suggest the following:
If you still have any good motors, protect them with the "fuse protected" cable (really a thermal switch) sold by Pitsco:
http://shop.pitsco.com/store/detail.aspx?ID=6122. These should be acceptable for use in competition, but minimally use them during test to prevent motor damage. I have not tried them, but they automatically reset and presumably can protect the motor (will they trip under "normal" load conditions though)?
If you have motors that are already burned out, it is indeed possible to repair them. You can carefully open them up by un-crimping the small tabs on the back cover. The hardest part of this is re-assembly because the brushes spring closed and you can't safely get them to go back over the commutator when trying to install the lid after repair. I found a good way to do this is to drill two small holes through the back plate 180 degrees apart next to the brushes (See attached diagram, thanks to Colin for the photo):
These holes allow you to insert small pins (safety pins for example) from the outside, holding the brushes in the open position while you re-install the cover plate. Once the cover is in position, then remove the pins and presto, the brushes are back in contact with the armature. I used a 0.036" PC board drill. You could use a more common 1/16" drill too.
You can replace the inductor with an equivalent (The best one I have seen was recommended by Patrick Freivald (Thanks Patrick)) --> Here:
http://www.mouser.com/Search/Product...lkey434-22-3R9
** Important ** -- Since these inductors burn out so easily, I would recommend repairing the motor by removing the inductor and replacing it with a jumper wire. That is what is shown on the attached diagram. Then install the new inductor EXTERNAL to the motor. You can put it in-line with the wire and cover it with heat shrink tubing. That way
when it fails again, you don't have to open the motor to fix it. I cannot imagine any sane person disputing that this is an exactly equivalent repair. Deleting the inductor would not be legal (although perfectly functional for prototyping), but if it is replaced externally, that is exactly equivalent.
-Tom