Originally Posted by Ruune

with the engine OFF, use your TX to hold the throttle at wide open (WOT). let go, and see how far back it goes. from there, try pushing the linkage closed. if there is any resistance from the carburetor, you've probably got a notch or it's misaligned. if not, your servo horn or servo gears may be stripped... or you may have a bad sensor in the servo.