My favorite little engine. I would test the armature with a ohm meter, should be between 1 and 2 ohms to each segment. Make sure you have good brush spring tenshion on both brushes, and a clean commentator and all electrical connections are soldered good. Sounds like you have to spin it to get it started..
Also take a ohm reading on the field, should read about 1ohm or a bit more.
Marty