1. Float Height: The most common reason for carburetor leaks is an incorrect float height. If the float height is too high, the fuel will overflow from the carburetor when the fuel level in the float bowl reaches that point. To adjust the float height, you will need to remove the carburetor bowls and adjust the floats so that they are parallel to the carburetor body when the float valve is closed.
2. Float Valve: If the float height is correct, the next thing to check is the float valve. The float valve is responsible for stopping the flow of fuel into the float bowl when the fuel level reaches a certain point. If the float valve is not seating properly, it can cause the fuel to overflow from the carburetor. To check the float valve, remove the carburetor bowls and inspect the float valve and its seat for any damage or wear. Replace the float valve if it is damaged.
3. Stuck Needle Valve: The needle valve is a small valve inside the float valve that controls the flow of fuel into the carburetor. If the needle valve is stuck open, it can cause the fuel to overflow from the carburetor. To check the needle valve, remove the carburetor bowls and inspect the needle valve for any damage or wear. Gently tap the needle valve with a small object to see if it moves freely. If the needle valve is stuck, replace it.
4. Damaged Gasket: If the carburetor bowls have been removed and refitted, it is possible that the gaskets between the carburetor bowls and the carburetor bodies are damaged, which can cause fuel leaks. Inspect the gaskets for any damage and replace them if necessary.
If you have tried all of these steps and the carburetors are still leaking, you may need to take them to a professional for further inspection and repair. Carburetor leaks can be a fire hazard, so it is important to address them as soon as possible.
