generator lopes in the motor mode

[Clem Clement]

I was fooling with my generator on my 39 peeekup trying to get the output right and it quit. I changed it out and am bench checking the thing. In the motor mode it really lopes rocking the case significantly. If I raise the adjustable brush it speeds up and smooths out. If I raise another brush it speeds up. If I raise the third brush it does not motor. If is move the adj brush rpm changfes but it still lopes??? Comutator is clean.
clem, needing more medicine