Ground loop related to VPI SDS/motor at 45 rpm?

I already tried the VPI motor oil. You just put a drop on the top of the spindle, right? I don't see where you tighten the black plastic pulley.

It's a hum or low buzz coming through the speakers...sounds like a ground loop to me. It only happens when I put the stylus on the record (and only when it's moving at 45 rpm). I suppose I could connect the pre-amp outputs to my oscilloscope to prove that it's 60 Hz, but that's what it sounds like to me.

I have since moved and am still getting a mid-frequency noise, but now it only seems to be coming from the motor itself, not being transmitted through the speakers. It's pretty loud. I don't have cones on the motor, just the original rubber feet. Do you think cones would help?

Is it on the black piece where the belt attaches? I don't see any small openings. There are two groves, either for the belt to fit in, and a flange just below them. The whole piece clamps down somehow on the motor's axle, but I don't wee any allen screws holding it on.
I also did some testing with my SDS. I changed the voltage from 102 to 96 and 108, and both of these voltages actually made the noise much worse.

The pulley has two different places, but they're the same size, so can't be 33 and 45. It only runs at 33 by itself as far as I can tell. So, can't tell if it's the motor or the SDS. It could be the motor, the SDS, or their interaction.