the trick is to have about 2000 rpm head rotor speed. the main gear is 102 tooth. motor pinion gear with give different ratios. for example, 9 tooth pinion with give about 11.3:1 ratio. mega 16/15/3 motor have 3000kv. that is 3000 rpm per volt. this motor can handle about 250watt of power. we know this combo works fairly well, so we can use this to compare different motor.

so what you want is motor that can handle at least 250watt. motor pinion gear depends upon the kv of motor if you have 1500kv motor, you need about 18tooth pinion. if you have 2400 kv motor, you need about 12 pinion. the minimum gear size available is 9 tooth. also anything over 22 tooth is hard to find as well.