Its interesting that this came up. When I built mine I tested every thing by moving the gears by hand to see if there was any binding(this was before I installed the 7:1 GRU) It would spin freely and then lock up. I'd try it again and it would be fine. Finely figured out there was enough shaft end play that it would catch the set screw periodically and lock up. As Travis said I simply offset the pinion slightly until it cleared the screw.
