RC10Talk - The Net's Largest Vintage R/C Community

I finished building my new tamiya dark impact today and it was all driving fine until I went from full reverse and slammed it into full forwards and it paused for a moment then went into about half full speed. If I then let go of the throttle trigger and squeezed it again the motor stops. If I extend it the motor speeds up and can't stop without turning off the buggy. I'm using a mtroniks viper auto sport tuned 20 esc and a standard tamiya torque tuned brushed motor. I also have a mad bull with the same esc, bought a week apart at the same mod shop that has the same issue with it. In both I'm using a etronix pulse radio and a 7.4v battery. Anyone have any ideas because I'm stumped?
Thanks