On my generator (a completely different model), the starter motor is a permanent magnet motor with four brushes, two positive and two ground. If one of the four brush connections fails, the motor still turns, but at half power, which in my case was barely enough to start it in the summertime and insufficient in the winter time...where trying to start it too hard/for too long I burned out some of the coils in the starter motor. :(
On the upside, the new starter motor with all the brushes and everything working properly cranks the generator much more vigorously and works like a charm.
