@clearthinker Please understand that my post here is meant to keep the physics correct and not to embarass you. You have a rudimentary understanding of some physics concepts, just enough to be dangerous, as they say.
Indeed, there is angular momentum, which is constant and once accelerted to speed, needs no force to maintain it. It is the acceleration that is different with mass (as I explained). As others have said, belt drives can struggle accelerating to speed, which is why many spin by hand before turning on. Once spinning all the motor has to overcome is the friction of the stylus, the load of the bearing (very low with a precision high end turntable) and losses in the belt and the motor. None of these change with mass.
Some might think friction increases with mass. Indeed it does when sliding a mass on an inclined plane for a high school physics problem. But with a precision bearing, there should be negligable difference with the mass added.
The exception I mentioned earlier would be a bad bearing that has more resistance to rotation with the increased mass.
Jerry