The motorcycle carburetors are probably the most misunderstood mechanical part on a motorcycle and many small engine machines. All engines require a proper mixture of air and fuel for combustion. The strange device known as the carburetor controls the ratio of the fuel/air mixture entering the engine.
This sounds simple enough, but there are many carburetors parts that, if not set properly, will at best cause the bike to run badly, or at worst keep it from running at all. The correct ratio of fuel and air is crucial for engine performance.
How Motorcycles Carburetors Works
Air enters the motorcycle carburetors from the air intake, and speeds up drastically, due to the narrowing of the interior walls of the carburetor. This air is blowing perpendicular to the throttle slide – a valve controlled from the throttle cable. When the throttle is open the cable raises the throttle slide located inside the carburetor’s main body. As the slide rises, the fast-moving air pulls the fuel up the main jet from the float chamber.
This works automatically because the fuel wants to travel from an area of high pressure (the float chamber) to an area of low pressure (the carburetor main body). Therefore, the fuel mixes with air and heads into the engine. The amount of fuel that flows is dependent on the position and size of the needle valve the size of the main jet. Also, eight-level of fuel in the float chamber. The fuel height in the float chamber is controlled by the floats.