A little late but.....so the voltage feeding the motor should be around 120 volts, and it is either off or on, the amount of time it is on obviously feeds more pellets. You say you have replaced the motor. Not burnt out I assume but still functional I'm guessing. I had this problem - the really crappy motor bearings wore out, thus the spinning rotor of the shaded pole motor would catch and miss a few turns here and there, all which added up to the problem you had. I can't vouch for why this is happening now, but maybe someone handed you a motor with the same problem. There are only a couple things that can go wrong here. There other being slippage where the set screw and the motor meet the auger, but I think the set screw would have to be way out for that to happen, if it can.
