Float Bowl Gasket The Ring That Stops the Leak

When a machine smells of petrol and there is a ring of oil staining under the carburetor, do not rush to change the whole carburetor. The most likely leak is the ring of gasket at the bottom of the float bowl. The float bowl gasket seals the joint between the float bowl and the carburetor body, so the fuel inside stays inside.

What is this gasket for? The carburetor is made in two halves, and the lower half is the float bowl, where the float sits and keeps the fuel level right. The bowl meets the body at a flange, and this ring of gasket sits in between, sealing the seam. The center of the gasket is cut open so the main jet and the fuel passages can pass through, and a separate o-ring seals the fuel inlet tube.

What does it look like? A black rubber sheet, round, with a long S shaped opening down the middle, a few small holes for the bolts and the fuel lines, and a small o-ring that comes with it. The o-ring sits in a groove on the fuel tube and seals the inlet.

Why does it leak? The gasket is rubber, living in fuel and close to the heat of the engine, and it takes a load every time the bowl is opened. Over time it hardens and warps, the sealing face no longer sits flat, and fuel weeps out around the flange. It is a wear item, not something that breaks, it ages.

How to replace it? Take the float bowl off, remove the old gasket, and wipe the flange face clean and flat, any left over bits of old gasket will keep the new one from sitting square. Fit the new gasket, line up the holes, press the o-ring into its groove on the fuel tube, and screw the bowl back on evenly. Then check that it no longer weeps.