If a float-type carburetor becomes flooded, what is the most likely cause?

A float-type carburetor becomes flooded primarily due to a leaking needle valve and seat assembly. The needle valve acts as a gate, regulating the flow of fuel into the carburetor's float chamber. When the float rises to a certain level, it presses against the needle valve, closing it off and stopping additional fuel from entering. If the needle valve or the seat becomes damaged or worn, it may not seal properly, allowing fuel to continuously flow into the float chamber even when the float is at the appropriate level. This overflow can lead to flooding, where excess fuel spills out of the carburetor, causing poor engine performance, difficulties starting, or stalling.

While excessive fuel pressure can also contribute to flooding, it's often linked to other issues like a malfunctioning fuel pump rather than a flaw within the carburetor itself. A faulty ignition coil and an incorrectly sized fuel injector do not impact the carburetor's ability to manage the fuel flow when it comes to flooding, as they deal more with combustion and fuel delivery in different contexts. Thus, the leaking needle valve and seat assembly is the most direct cause of a flooded float-type carburetor.