you said that the idle mixture is not affecting anything - this is bad, it means that something else than the idle circuit is making the engine idle - the only circuit that is above the idle circuit is the primary jet circuit - the secondary jet circuit is above both.
The top hat of the carburettor has tiny air passages in it to "foam" the fuel and be properly utilised in the idle circuit at the throttle opening. If it is plugged - the fuel quantity increases ten fold as raw liquid is sucked (black smoke). If its clean then recheck the float height for correct working and also check that the throats are installed correctly - infact the engine should idle even with primary and secondary jets blocked. The idle circuit takes care of that.
how a carby works
1 - idle speed = idle to fast idle rpm
2 - 1000 rpm to midrange - 3000 rpm plus idle circuit (primary throttle open, secondary closed)
3 - 3000 - 6000 rpm = secondary circuit plus primary circuit plus idle circuit. (both throttles opened fully)