Combines 2188 with a vibration

Have you tried operating the separator with the rotor out of gearIJ Sometimes a defective peripheral component (shoe bushings come to mind here) will create the impression that the rotor is unbalanced.

Yes we have tried that too and then vibration seems to stop.

the rubber bushings are bad in your rotor drive plate at the rear of the rotor...if they are the rotor has to come out...later models have a different plate, you can get the update kit.

I suspect that Dave is correct, and likely the bolts which hold the spline to the rear of the rotor are probably bent, as well.