B44 gearing: whay cant I nail it?

[danny the elfman]

hey guys. I can never seem to get the gearing right on my b44, its always over heats. Im running a 6.5t hpi flux sensored motor (great motor by the way) but after about 8 mins of use it burnt me when i touched (thank god it didnt break, it gave me a blister ) Right now its get the stock spur, and a 22t pinion. Any suggestions on what pinion? thanks