Carburetor Kit Two Flat Pieces, Most Failure Points

There are two spots on a carburetor that fail the fastest, and these two pieces each take one. The WM80 repair kit is just that, one diaphragm, one gasket.

Why these two? Take the carburetor apart and the rubber that ages is in a few places, but two of them are the killers. The metering diaphragm moves the fuel, and when it fails, fuel does not come up, the engine will not start or has no pull. The main gasket seals the joint, and when it ages, fuel weeps out between the carburetor and the body. The two, one diaphragm and one gasket, one for the fuel path and one for the seal, and they fail in different ways. So one teardown, both pieces in, and do not leave the job half done.

What does the diaphragm piece look like? Black rubber, a rectangular flange with six holes, a recessed center, and a metal plate in the middle, five round holes around a small central pin. It sits in the metering diaphragm chamber, the plate against the pump seat, swelling and contracting to draw fuel. Hardened, cracked, or the five holes wearing ragged, and it is time to swap it.

What does the gasket piece look like? A dark gray square, a large hole in the center, six bolt holes around it. It sits between the carburetor and the body, the big hole facing the cylinder, the bolt holes on the corner and side studs. Squashed, its edges curled, or the spots that wept gone soft and yellowed, and it is time to swap it.

How to fit both in one teardown? Photograph the old parts first. Press the diaphragm flat into its chamber with no wrinkles, the metal plate toward the pump seat, the six holes lined up. Fit the gasket dry with no oil, the six holes on the studs, and the corner screws in diagonally, a little at a time, so the gasket is not crushed in one spot. Once fitted, pump fuel by hand a couple of times and check the flow, then start it and look at the joint for weeping.

When not to tear it down? The machine still runs, the idle is just a touch off; flush the carburetor first and see. Once you know the diaphragm has hardened or the gasket is weeping, tear it down and put both in. Since it is open anyway, both at once saves a second job.