Starter bench test spins slow

[ghalperin]

The starter on my 29 was spinning slow. 6 volt battery and all connections were fine. I installed my spare starter and everything is fine. Now I need to fix the slow starter. I disassembled the slow spinning starter and the only thing that I noticed odd was the insulation on the insulated brushes was falling off. One of the insulated brushes had pretty shinny wire where the insulation had fallen off, maybe it was shorting there. Is there a good tutorial online for starter component testing and inspection? What could I use to replace the insulation on the wire for the brushes?