either the bearing is bad or maybe it is rubbung on the screw on the end of the clutchbell. Lossen that a 1/2 a turn and see it that is it. if not pull the motor out and check the bearing first by taking of the clutch shoes then put the bell back on and spin it. if it spins freely maybe the clutch is rubbing on the clutchnell. trim the trailng edge of the shoes about 1/16 of a inch to make the overall diameter smaller. it sounds like that could be the problem or maybe the clutch shoes are not pushed on the tabs all the way. this will also make it rub. good luck. if worst come to worse take the motor in the to hobby shop and they should be able to figure it out.