Can you run the motor away from the turntable to see if the noise is still present? If it isn't, double check that the pulley isn't rubbing against the platter. That happened to me once and I had a bit of a freak out. Check the power cord where it attaches to the back of the motor and ensure it isn't contacting the back leg of the turntable. That's all I can think of.
P.S. There is some resistance when turning the motor. On my 300rpm not much, but it can just be felt.
P.S. There is some resistance when turning the motor. On my 300rpm not much, but it can just be felt.