I was thinking of that but the hole itself is quite deep so I used a bottoming tap and that worked well in conbination with lock tite. If that doesn't work I/4"x28 wil work and cut threads easily since the carb is made from zimac (but a bottoming tap must be used as not to break through the carb's wall), A 1/4 inch round head screw would work with no modification a washer sits under the screw head. Not too tight the throttle knocker must freely pivot. The machining aspect of the repair is easy BUT how does the dam thing work....carburetors to me as Winston Churchill once said, " are an enigma wrapped in a mystery".
Steve