Problems with brushless truggy

I am having a problem with something on my brushless system, I have a bk warrior 9918 and a bk warrior 9920 and a nemesis blue 7XL motor, the problem that I am having is that it cuts out after about 2 laps.
I have replaced everything except the motor. I replaced things like wires, radios, recievers, and speed controllers. If it is the motor could it be fixed?
I am running 6 cell nimh packs in a series.
I am thinking that maybe I need a bec?