if its shutting down then you have the idle too low or it is not stopping at the set idle stop. when you hit the breaks it closes the throttle too far, so you need to set it so when you hit the breaks and turn the idle set screw till it stops at about 1mm or 1.5mm. if the idle stop is not being used and you have it set by the radio settings only it will go past it and close the carb and shut it down.