Obviously over fueling - possible causes; (outside the carb) dirty air filter or obstructed air intake duct (inside the carb) incorrect float level, damaged slide diaphragm not lifting slide properly (pin hole in the diaphragm can do this), clogged internal vacuum passage to slide vacuum chamber, jet loose or fell out inside float bowl, leaky o-ring sealing float needle seat to carb body, damaged main or pilot jet, slide needle not assembled correctly, damaged, incorrectly installed or missing vacuum slide spring.
There are other possibilities within the carb, but it depends on the definition of 'thoroughly cleaned' - for some, thoroughly cleaning is taking the carb apart and spraying it with aerosol cleaner, for other is taking the carb apart and soaking in Simple Green, others wash it in gasoline and call it done. To me thoroughly cleaning is total disassembly (removing every non-pressed in part) and cleaning all the parts in a heated sonic cleaner with a specialized cleaning solution. The cleaning solution I use cost $100 a gallon. Heated to 180 degrees F, it will remove paint from the exterior of a carb, but it will not harm rubber. It removes varnish, oxidation and algae (algae grows in side the float bowl due to alcohol carrying water into the chamber).
Alcohol can be derived from many sources. Methanol alcohol was distilled from wood, Ethanol is produced from grains or other renewable agricultural and forestry feedstocks. Isopropyl alcohol is primarily produced by combining water and propene in a hydration reaction. And there are many other types of alcohol, but the three aforementioned are the most common, produced in large quantities and commonly mixed with gasoline. To learn more about alcohol, go to https://www.sciencedirect.com/
Before alcohol can be blended with gasoline, it has to be dried - distilled alcohol contains a small percentage of water - ethanol must have at least 99.2% purity , which is obtained by dehydration or drying of the ethanol after the distillation. As little as .4% water in a gallon of gas will cause ethanol to separate from gasoline.
I digress - check the intake and re-rebuild the carb if no restrictions are found to the air induction.