I have had a somewhat similar smoking issue, I had a silver can that smoked if you put in more than 2v. usually a SC motor draws about 1amp on 2v, during run-in, but this one would draw about 4 amps on 1v, 8 amps on 2v and my charger (on run-in mode) would cut power to the motor when it drew more than 10amps. the motor got replaced under warranty, I think the problem was that the bushes (you would have bearings) were out of alignment, and being a SC, they are sealed and inaccessable. I'd check the bearing are correctly seated, and try again...
hope this helps
GTB SS + 13.5 & 10.5