John, a bad float is normally one of two things. The float itself may have a pinhole in it and actually sink instead of float. You can check this by putting it into a small container filled with gasoline and watch to see if it sinks. The other problem is the float out of adjustment. The arm from the float to the hinge may become bent so much that the float does not push up on the needle valve and shut off fuel. You can correct this by slightly bending the float hinge lever. Didn't your kit come with instructions for assembly and adjustment?
Take the carburetor off the tractor and remove the float bowl. Turn the carburetor upside-down and measure the distance between the float bulbs and the body of the carburetor. It should be 1/4" or 0.25". Or, if a pencil is exactly 1/4" thick, you should be able to slide it under the bulbs from side-to-side. If it's greater than .30" , it's out of tolerance.
The most common float problem is trash in the float valve. While you have the float chamber apart, clean out any trash and make sure the needle valve will shut off the fuel. If you have to, put the fuel line to the carb and see if the fuel stops flowing while you lightly push up on the float bulb. I'm just sure you will find trash, a damaged float valve, or a damaged float valve seat. Most often it's just trash. Good luck! /forums/images/graemlins/smile.gif