A tiller carburetor is a device that is used to meter the amounts of fuel and air that are allowed to enter the combustion chamber of a tiller engine. Containing the high-speed, slow-speed and choke controls, the tiller carburetor is similar to a carburetor that is used on a snow-blower or lawnmower engine. Unlike an automobile carburetor, the tiller carburetor does not include an accelerator pump.
The tiller carburetor controls the engine's power when running and idling. By allowing in a precise amount of fuel and air, the tiller carburetor can make the engine rev very fast, idle very slow or operate anywhere in between. The carburetor is one of the most important components on an engine, and it commands the engine on how to operate. Fuel and air are not simply allowed to pass through the carburetor; rather, the two are carefully metered by internal components within the carburetor and atomized into a fine mist. The mist is pulled into the engine by the vacuum that is created by the piston.
After the piston has sucked the air-and-fuel mixture into the combustion chamber, the piston compresses the mixture, and the spark plug ignites the mixture, sending the piston back down. As the piston rises back up through the cylinder, the exhaust is pushed out of the engine through the exhaust valve and into the exhaust system. This is what is known as the combustion process of the four-cycle engine. Most tillers utilize the four-cylinder engine, but some use the two-cycle engine. These engines use specialized carburetors that are designed to operate with the two-cycle oil mixed into the fuel tank.
One of the most common problems with a tiller carburetor is the buildup of varnish in the carburetor. This occurs when the machine is allowed to sit long periods with fuel in the gas tank and carburetor. The fuel leaves a varnish-like coating on the interior components of the fuel system as it ages, requiring cleaning prior to operating after a long nonoperative period. This problem usually can be taken care of by spraying an aerosol carburetor cleaner into the tiller carburetor and allowing the cleaner to sit for several minutes. It might be necessary to repeat this procedure several times, depending on the duration for which the tiller has been idle.
Occasionally, the tiller carburetor will require removal to properly clean out the varnish. This is accomplished by removing the air filter and the other small, mounting screws on the carburetor. The complete removal can sometimes be forgone by spraying the cleaner into all of the ports and openings of the carburetor and allowing it to sit before reassembling and putting gasoline back into the fuel tank.