hey fella, i had the same thing happen to my old hyper 7. all i did was attatch a spare exhaust spring to the throttle servo horn and the other end to the inlet tube of the carby. works fantastic. REMEMBERING THIS ONLY WORKS FOR THE CAR BATTERY. you should still install a failsafe for your radio. ($40 investment to protect $800 toy). just cut the spring so it has enough tension on it to pull the servo back to idle. do this buy turning on the power on both the car and the radio. then open throttle up, leave radio on and turn off you car. pull spring so the throttle comes to idle. cut the spring to suit that position. now you have a (mechanical fail safe)

hope this helps.