Vertical upright, swing-arm and generator install 3 of 7.
2) Install the Brass spindle on the motor shaft with the two set screws closer to the motor.
When lightly pushing on the motor shaft leave between 3/32" and 1/8" between the spindle and the motor.
Tighten very very lightly both set screws and back them off about 1/8 of a turn so you can slide the spindle back and forth to allow a nice alignment on the two flats of the motor shaft.
I you have purple or blue removable Locktite, apply to the threads of one setscrew and tighten hard, then apply to the threads of the second setscrew and tighten that one hard. If you don't have any Locktight, give just tightening the setscrews a try. If by chance they loosen, you could give clear nail polish a try instead of Locktight if you happen to have some on hand. Be careful in either instance you don't fill the recessed Allen hole in the setscrew.
When tightening the setscrews use a good quality Allen wrench. If you by chance strip the wrench, you can usually grind a little at a time off using a belt sander or grindstone dipping in water to cool between cuts until a fresh portion of the wrench is exposed.