Done properly it needs removing, and all stripping down, then leave to soak in thinners in a tub overnight if you can, it is a MUST that you remove all items with rubber or plastic on them from carb, otherwise thinners will ruin them, this is mainly o rings and diaphragms.
Thinners will get it spotless, don't forget where everything goes!!
The trouble bit is normally dirt/crap in the float chamber, this makes the float valve jam open, flooding the float chamber and causing flooding rich running of the engine, to clean this out normally just invert the carb, remove float pivot pin, and then float then blow through all openings as said with air line.
tabetha