New Servo Dead?
 

I just bought a new Hitec 645 mg throttle / brake servo for my 1/8th buggy (OFNA Hyper 7). I installed it and turned on my tx to see if it worked. When I go full throttle it works fine, when I release it centers back to throttle closed. Then I hit the brakes and it works fine, but when I release it centers back to half throttle. If I hit full throttle again and release it centers back to closed throttle again. I am not sure why but it seems like it wont go back to closed throttle after I hit the brakes, and I've tried mounting the servo horn every way imaginable so I am not sure whats wrong?

Seems that the rod that goes between the servo horn & the carb is hanging up, loosen up the screw that holds the piece were the rod runs thru on the servo horn, also try a little lube on the rod. Hope this helps.