If fuel is dripping from the carburetor when the engine is off, or the tractor is blowing black smoke and fouling plugs, it is getting too much fuel.

• Float valve not seating: The needle valve may have a groove worn into it, or dirt is preventing it from sealing. If you have a viton-tipped needle, clean it with mineral sprits and flush the seat out. If you can see visible damage to the needle tip, replace it.
• Heavy or sinking float: If the float develops a pinhole leak (brass floats) or absorbs fuel (cork or nitrophyl floats), it will sink and hold the fuel valve open. Submerge a brass float in near-boiling water, if you see bubbles it has a leak and must be replaced.
• Incorrect float height: The float must shut off fuel at the correct level or the bowl may overflow.
• Excessive fuel pressure: If you added an electric fuel pump to a gravity-fed system, the pressure might be overpowering the float needle. An in-line pressure regulator will allow you to dial it back.