Well the rear brake is free and not dragging, the rear bearings aren't being squished by the mounting bolts, and the rear wheel turns freely if the drive chain is removed. With the drive chain on however, there's a lot of drag and it doesn't turn freely. The chain itself is new, well oiled, and flexible, so it's not that. The front sprocket is brand new, so I'm not sure if that may be somehow contributing to it. My guess is that it's something in the transmission. So now I need to learn how to change transmission fluid. I'll do that after the weekend, since I'm heading up to Boston tomorrow.
Even still, I just took it down the road and it 40 on a downhill. Once I get this issue sorted out I know it'll go faster, but 40 on a moped is pretty damn fun.