You might want to try between 14 up to 20 degrees at idle up to 2000 RPM and up to 30 degrees above 2000 RPM
That carb should idle on the idle circuit only unless one of the idle fuel feed circuits is plug up or maybe it is defective
When you open up the air bleeds, all three circuits or two circuit carbs., you are leaning that circuit out, if you make the air bleed holes smaller you will richen it up