[ricard]

I don't think so. The way the motor operates normally is that the rotor rests against a thrust bearing at the bottom of the motor, and the magnetic field is not powerful enough to lift it from the bearing (there is a bit of play). The grease in the thrust bearing had hardened and I replaced it with new fresh grease. Again, the motor turns freely when rotated by hand in this state.

When operated upside down, the rotor would seem to scrape against the end of the stator radial bearing. In fact there seemed to be some sort of a cork washer here (together with a metal one), or other material that had disintegrated as could be observed when the motor was opened.

But it's an interesting theory, I'll try it and see what happens. Just standing the machine up so the machine operates on its side would relieve the lower thrust bearing from its task.

Incidentally, on another model 6 I have the motor design indeed seems to be upside down, i.e. instead of the rotor resting on a thrust bearing, the stator is at the bottom and the motor rests on that.