I had one of my motors do that too... If u took it apart and didnt change anything, then it's just you tighten the flywheel to tight. Try backing out the flywheel nut a bit and see if that helps. The problem i was having was a washer i put behind the flywheel and when i cranked down on the nut it pinched it between the flywheel and bearing and it would'nt spin. Hope this helps, let us know if you got it to turn freely