Also, a 50c pack doesn't really have the punch to power that motor effectively. I'd stick with higher c rated packs in the 100c or more range. I run 39T spur gears from either MIP or Robinson Racing with a 15T or 16T pinion on large outdoor tracks. Indoors I run the same spur gear, usually with a 14T pinion. As long as you're not overheating you should be fine. 12T is just too small to be fast on a large track with a low kV motor.