I have a copy of the Rosenburg/Hand book mentioned in jbartos' link, it is expensive but I can recommend it. There is a lot of practical knowledge on fault-finding and repair of many types of motor, although it doesn't cover the large bar-wound type machines and it is a little bit dated.
I also have a copy of Augie Hand's later book "Electric Motor Maintenance and Troubleshooting", it is more up to date but I was a little disappointed with it, for it's price it isn't what I would call comprehensive.
I am sure there are other repair books around. I have an old copy of "Rewinding and Repair of Electric Motors" by Karl Wilkinson, published in the UK, old-fashioned and out of print but it's a gem. It shows all the old tricks of the trade, how to make the jigs and tooling etc.