Bigger motors on riding mowers boost not only mowing electricity but also their ability to power accessories like snowplows — and the Briggs & Stratton 15-horsepower engine is utilized by numerous lawn tractor manufacturers. This workhorse engine, like others, requires regular maintenance for smooth performance. Many components can lead to limiting flow of fuel into the engine, but repeated draining of gasoline into the engine typically outlines back into the carburetor.
About the Carburetor
The carburetor manages fuel as it flows from tank to engine, combining fuel and air to provide the volatile vapor necessary for combustion. Fuel moves from the tank by the vacuum formed in the bowl as gasoline leaves the carburetor for the engine. Exiting fuel moves through a very small orifice controlled by a pointed pin, called a needle, mounted on the hinge end of a nest that rises and rises as fuel enters the carburetor from the gas cylinder. On a 15-horsepower Briggs & Stratton engine, the carburetor sits behind the air filter, next to the engine.
What Can Go Wrong
Clogged fuel lines, dirty air and fuel filters and defective starters every cause stalling, however, the carburetor controls the volume of fuel sent into the engine. Worn or broken gaskets, one around the rim of the carburetor’s bowl along with the other that seals the opening to your nut on its underside, can create leakage below the carburetor. A worn shutter between the carburetor and the engine — or one that is stuck open due to dirt or gunky oil seams from old gasoline — allows gas to flow straight through from the fuel tank to the engine, flood and stalling the piston.
Needle in the Valve Kit
The collection of tiny components known as the valve controls the flow, provided all else is functioning correctly. The doughnut-shaped float sits in the bowl, rising and dropping on a hinge as fuel flows out and in. The needle valve sits in a slot on the float and meters the correct amount of fuel. The needle rises and falls inside a small passage against a very small gasket. This motion allows just the right amount of petrol to climb in the carburetor’s main chamber where it mixes with air, and then vaporizes and shoots into the engine through the shutter. If the needle slides out of the passing, the gasket shrinks or breaks, or so the hinge pin on the nest breaks or breaks out, then there is no control over the flow of gas into the main chamber, and fluid gas will operate, unimpeded, from the fuel tank into the engine.
Liquid gasoline running into and over a hot engine poses a hazard of fire, therefore keeping your mower’s carburetor clean and in proper condition is vital. Cleaning the interior with carburetor cleaner and replacing worn gaskets ought to be a part of yearly maintenance. Rather than using dirty or worn valve components, replacement of the hinge pin, needle and gasket will guarantee proper operation. All necessary parts can be found in inexpensive valve kits.