Why is the drain pipe of a motorcycle carburetor leaking oil?

[VanRose]

Below is an analysis of the reasons for oil leakage from the drain pipe of a motorcycle carburetor: Debris on the contact surface between the needle valve and valve seat: The needle valve and valve seat control the fuel intake, requiring strict sealing with a high surface finish. If debris accumulates on the contact surface, it can lead to poor sealing between the needle valve and valve seat, resulting in oil leakage. Debris mainly refers to impurities and condensed gum in gasoline. To prevent such issues, users should regularly clean the fuel filter and use high-quality gasoline. Needle valve wear: During use, the needle valve can wear due to prolonged exposure to impurities in gasoline and contact with the valve seat; an unbalanced adjustment at both ends of the float can cause lateral force on the needle valve, leading to wear. Worn needle valves result in poor sealing of the valve seat, causing oil leakage.