been fighting a weird symptom with my carb adjustments. The right side bing would not respond to the idle mixture screw and it took the idle adjustment to be not touching the stop to get them balanced. And then only by upping the left side so it idled at 1300 ish. Started by taking out the idle adjustment screw and was going to check the passages again. Then realized one of the butterfly screws was "hanging by a thread"
furthermore it was stripped so I could not just screw it back down.
Ended up finding a counter sunk american screw that would slip in there and then put a nut on the back with locktite. It will cause a bit of restriction at the top end, but got me going. All I can imagine is that screw coming out and getting lodged in a valve and the engine going