I have a Predator 212 go cart with a Mikuni carb upgrade but I can't get it to idle slow enough so the clutch isn't engaged and I want to know what I can do to fix that. I also messed with the two carb set screws and I wanted to know what the factory starting position should be as in how many turns.
I have a video for common issues when installing a Mikuni carb.
The screw under the front of the carb next to the bowl is an fuel screw. Gently seat that screw in and turn 2 turns out (720 degrees) that is a good baseline for that. The screw on top of the carb is the manual idle adjustment that moves the slide up and down. There is no preset value set for that. Start that by looking into the carb and see that the slide is just slightly open and adjust once the engine is warmed up The lever when pushed down opens a circuit that allows for additional fuel needed for cold start an engine. The run position is to have the lever up with the plunger down into the carb body.
A high idle could be a vacuum leak when the o-ring is not sealed to the manifold or the slide in the carb can be up higher than needed.