If you don't have a parts washer or bead blaster, you might try this out. Soak your carb for 5 minutes in phosphoric acid (concrete floor etch - thanks LC). Remove the jets first including the needle seat. While the carb is in the bath, give it a scrub with a toothbrush.. 5 minutes tops. Pull it out and dunk in water. Then rub it up all over with Nev'r Dull (that cotton soaked stuff) to prevent it from going black.
You'll go from this:
In about 15 minutes - total!