Sounds like a "gunky" stuck float valve, which I've mentioned before. I thought I needed a new CDI, but it was a leaky valve. Dog is correct about turning the supply petcock off, if it is a stuck open float valve you can end up with a crank case full of gasoline. Ask me how I know.

Every normal man must be tempted, at times, to spit on his hands, hoist the black flag, and begin slitting throats. H. L. Mencken