Why is my riding mower leaking oil or gas?

Replace the riding mower carburetor assembly

The carburetor mixes gas with air before the fuel goes into the cylinder. If the gas/air mix isn't balanced, the engine won't start or the engine will run rough and stall when you try to drive the riding mower. A damaged carburetor may also leak gas. Replace the carburetor if it causes any of these symptoms.

Rebuild the riding mower engine carburetor

The carburetor mixes fuel with air to create a combustible mixture that enters the engine cylinder and ignites to drive the piston. Impurities in gasoline can clog the carburetor, preventing the engine from starting. Carburetor clogs can also cause the engine to run rough and the engine may stall when you try to drive the riding mower. Seals and gaskets in the carburetor eventually wear out and can leak gas. Use a carburetor rebuild kit to refurbish a clogged or leaking carburetor.

Replace the riding mower head gasket

If you notice an oil leak and your mower's engine can't reach normal operating speed or the mower struggles to climb a hill, the engine may have blown the head gasket. The head gasket seals the cylinder head to the top of the engine. Air leaking past a damaged head gasket reduces cylinder compression causing a loss of power. A blown head gasket leaks oil because the gasket doesn't seal the cylinder head mounting surfaces. Replace the head gasket if it leaks.

Replace the riding mower fuel pump

The fuel pump moves fuel to the engine from the fuel tank on the riding mower or lawn tractor fuel tank. If the engine won't start or quits after starting, the fuel pump might not be working. A cracked fuel pump leaks gasoline. Replace the fuel pump if it leaks or doesn't pump fuel to the carburetor.