A friend had his Makergear M2 filament drive motor stop driving the filament; the problem turned out to be a severely worn pinion gear on the motor shaft. Perhaps Makergear got a pallet of bad motors, as the problem seems to affect a batch of printers made during the middle of 2013, more or less.
The motor on my printer came off the line in early 2013, if that’s really a date code:
There’s no manufacturer, but the 104022 number matches up with a Kysan motor. The description doesn’t say anything about the interior of the gearbox, but that’s not surprising. The gear ratio is 5.2:1, not the 5:1 I’d been assuming, which gets compensated out later on.
The pinion gear is worn, but not severely, and the three planet gears are in fine shape:
Slather everything with lithium gear grease, stuff the parts back in place, and it’s all good.
The socket-head set screws may have a bit of threadlock, as they’re firmly set in place, and, as you’d expect, Harbor Freight hex wrenches are made of butter-soft steel that’s totally useless in sizes below about 2.5 mm. In fact, those screws rounded the end of an old Craftsman wrench, so maybe they’re slightly oversize.