[CajunSpike]

Generally powder in the bottom of a carb bowl means the left over fuel in the bowl dried out totally. It left behind chemicals that were in the fuel that appear as a powder.

Another side effect is that that powder can clog up the main jet in the bowl, preventing the fuel from flowing right, and causing engine running problems.

Have to remove the jets from the bowl carefully.
Clean all the small openings of the jet and the bowl itself.
Reassemble and try again.