What carb? Good filter between mech pump & carb? I'd check & maybe replace the needle/seat assy & make sure the float ain't hanging up anywhere thru its' travel nor taking on fuel (waterlogged). Idle fuel psi not close to the edge (eddy). might fix a thin red straw to a can of starting fluid & blast a 2 second shot into each idle mixture xrew port tho with it going rich like that I'd be more inclined to think that it's a needle/seat issue rather than dirt in the idle circuit which that usually just makes it die. IF no luck you might check all the carbs' gaskets (correct ones/ correct side up or down/screw tightness. EDIT & blast out all the passages with starting fluid or brake kleen. Holler how it goes