Re: Engine won't go past 30MPH
IMHO, the best way is to let your local terrain will determine your gear ratio.
if you live in a flat area it doesn't matter, go with which ever you like best. the stock 44t is a nice "middle of the road" choice. (no pun intended)
i tried a 28, 32, 44, 50 and finally settled on a 56.
the smaller ones dramatically increase top end speed on level ground, but they DO NOT climb hills. even a moderate grade will eventually defeat them over a long incline.
gear for the terrain that you will actually be riding on.
my top speed on level ground is around 25-30 mph, with 29er wheels.
It will be "done" when it can climb trees, go 300 mph, and fire lasers from the headlights. Surface to air missiles would be nice too.