What Causes a Motorcycle Carburetor to Not Spray Fuel?
2 Answers
Motorcycle carburetors do not spray fuel; instead, fuel is drawn in by the negative pressure created by piston movement, similar to how a syringe draws in water or air. Below is supplementary information about carburetors: How a Carburetor Works: A carburetor supplies fuel to the engine mechanically, and the relationship between fuel supply and engine speed or throttle opening is linear. It cannot ensure the ideal air-fuel ratio under all operating conditions and environments. Additionally, when the engine's state changes, the carburetor cannot adapt accordingly, leading to significant energy waste, poor combustion, increased fuel consumption, and worsened emissions. Components of a Carburetor: A simple carburetor consists of three parts: upper, middle, and lower. The upper part includes the air intake and float chamber, the middle part contains the venturi, jet, and spray tube, and the lower part includes the throttle valve, among others. The float chamber is a rectangular container that stores fuel from the fuel pump, with a float inside that controls the fuel intake based on the fuel level. The spray tube in the middle section has one end connected to the jet in the float chamber and the other end opening at the throat of the venturi.
When I used to repair motorcycles, I encountered many cases where the carburetor failed to spray fuel. Common causes included clogged fuel nozzles, such as impurities in the fuel tank or dirty fuel accumulating into deposits that block the fuel passages; issues with the float chamber, where the float gets stuck, preventing fuel flow; fuel pump failure, resulting in insufficient pressure to supply fuel; or poor external air mixing affecting the fuel-air ratio. If it's difficult to start in cold weather, there might be fuel condensation. It's recommended to first check the fuel level in the tank and whether the fuel pump sounds normal, then try using a cleaner to blow through the fuel nozzle. If DIY doesn’t work, you’ll need to go to a professional shop for disassembly and maintenance. Regularly using high-quality gasoline and cleaning the carburetor can significantly reduce this risk. Especially for older bikes, parts wear out faster, so more frequent checks and repairs are necessary.
