The motor runs well; however, there is an inconsistency in the noise. The noise is not at a constant sound and seems to have a regular change. Is this common or something of concern?
Depends. Remove the honing wheel and drive wheel and see if it makes the same "variation". If it goes away it is in the drive, if not in the motor. It may be bearings or some change in the drive wheel. But without hearing it it would be difficult to say. If it runs well and the sound is not too harsh, as in a worn bearing, then I would not worry.