I had a carter 625, and despite my best efforts the idle mixture screws would not respond I posted asking what the problem was and was told it needed a rebuild so I took it apart and other than a jet being installed improperly, which didn't fix it , there was nothing visibly wrong even rebuilt it wouldn't respond so, I decided enough is enough an d put an edelbrock on it and it runs like a top.
All I can figure is that the idle mixture circuit was damaged, or one of the other circuits. Which to my knowledge makes the carter an expensive paper weight.
