Lawn Mower Carburetor Is Leaking

Gaskets

• Any place two pieces of metal meet in the carburetor, there is a gasket made of rubber or similar material that forms a tight seal. Exposure to dirt, rust particles and ultraviolet light breaks down gaskets until they become stiff and cracked, allowing fuel to leak out. Replace worn gaskets as soon as you notice them. Extend the life of your existing gaskets by lubricating them with a small amount of engine oil whenever you clean or service the carburetor.

Linkages and Screws

• A carburetor is adjusted by tiny screws and linkages that control the amount of fuel that gets through and the speed at which the engine idles. Called the main mixture adjustment screw, the idle adjustment screw and the governor linkage, these components are adjacent chambers that contain gasoline. If they are cracked or otherwise damaged, they can cause a leak and will need to be replaced. The correct adjustment for these parts is delicate and varies from one manufacturer to another, so consult your owner's manual.

Carburetor Float

• Fuel flows from the fuel line into the bowl of the carburetor to supply the engine. To prevent an oversupply of fuel, the carburetor uses a float system that turns off the flow when the bowl is full. This float is usually a hollow, horseshoe-shaped piece of metal or plastic with a hinge at the toe end of the horseshoe. If the float is bent so that it cannot rise and fall freely, or if it gets a hole and fills with fuel so that it no longer floats, fuel is never cut off and floods the carburetor, leaking out of any weak spots in gaskets or around screws.

Needle Valve

• The actual mechanism by which the float stops fuel overflow is called a needle valve. The cone-shaped metal needle sits on top of the float. When the float is resting on top of a full bowl of fuel, the needle nestles snugly into a hole leading from the fuel line, closing it off. Even if the float itself is working correctly, dirt or corrosion on the needle or in the hole prevents it from closing completely, allowing the carburetor to flood and leak.