What could cause the carburetor to run too lean?

A carburetor running too lean means that there is an inadequate amount of fuel being mixed with air, resulting in an overly rich air-fuel mixture that can lead to various performance issues. The most common reason for a lean condition in the carburetor is an insufficient fuel supply. Several factors can contribute to this situation, such as a clogged fuel filter, a malfunctioning fuel pump, or even issues with the fuel lines. When the fuel supply is compromised, the carburetor cannot draw enough fuel, which leads to a lean mixture.

In this context, having a dirty air filter primarily affects the air entering the carburetor, but it does not directly cause the fuel supply to decrease. An overfilled gas tank may lead to fuel vaporization issues, but it generally wouldn’t create a lean condition in the carburetor itself. Lastly, a coolant system malfunction is more related to temperature regulation rather than directly impacting the fuel mixture in the carburetor. Therefore, the option regarding insufficient fuel supply accurately describes a primary cause of a carburetor running too lean.