I bought a used 36" Gravely with a 12.5 Kawasaki engine. The engine is flooding when I try to start it. I can see gas dripping from the place where the muffler port meets the manifold. After about 20 pulls, the beast starts up with a vast amount of white smoke blowing out of the muffler and the manifold. When I pull off the air cleaner, I can see gas sitting in the carburetor. What adjustments can I make to the carburetor? I have adjusted many Briggs engines, but this is my first Kawasaki. There is a screw on the bottom of the float bowl. What is that for? Any help would be greatly appreciated.