Hi, I just purchased a car from a man in rochester. It is a stampede xl5 that has been converted to a brushless mamba 5700 with a sidewinder ESC. Currently, the only battery I have with the proper connecter is a 4600 6-cell 7.2 volt battery. When i lift the truck in the air, and hit the throttle (after a fresh calibration) it punches and flies just fine. As soon as i set it down and try to push the throttle, it stutters and chatters for a few seconds, then takes off, or doesnt take off at all, and i have to tickle the throttle. Can anyone tell me why this might be happening. I do have everything secured and fastened, and my current gearing in the Pede is 14/86. Thanks!