Can I bypass the control board to test the motor?

@eraskin yes it is. Use thios guide KitchenAid Professional 600 Drive Motor Replacement and disconnect the motor controller from the motor. Then apply power directly to the motor. How you accomplish that, will depend on what you have available. I would use test leads with alligator clips, and come of the main power supply from the mixer. Of course, you can also just take a stripped power cable and use that :-) Whatever you got .... It'll buck since it will get a full load so make sure everything is clear in the transmission etc.