What gearing

your gearing will depend on several factors.engine mods,tire size and riding style,also personal preference.give a mod list with tire size and general terrain being ridden and someone can give you a good idea of what will work.
 
if you want more top speed with less exeleration then use a bigger front sproket(14)or a smaller rear one(38)

but if you want more exeleration and less top speed then use a smaller front (12)or a bigger rear(42)