Help VPI SDS Issue

I took the plunge and got the SDS. Wow what a difference but I am having an issue. (I am using the 600 rpm motor) In order to get the motor to spin the platter I have to push it to start it moving. The motor is on but it sound like to is hesistating. I unplugged the SDS and no issue it starts right away. Is this an issue with the 600 vs 300 motor?