Which term does not represent a type of carburetor found on small gasoline engines?

The term "nozzle feed" does not represent a commonly recognized type of carburetor used in small gasoline engines. Instead, the other terms refer to established designs within carburetor technology.

Float feed carburetors are widely used and rely on a float mechanism to maintain a constant fuel level in the float chamber, ensuring a consistent fuel supply as the engine demands it. Vacuum feed carburetors operate by using engine vacuum to draw fuel from the float chamber, allowing for automatic fuel regulation based on engine speed and load. Diaphragm feed carburetors utilize a diaphragm that responds to engine vacuum or pressure changes, helping control the fuel flow effectively, particularly in applications with varying engine speeds.

The absence of "nozzle feed" in the list of carburetor types indicates that it is not a standard designation in small engine mechanics, making it the correct choice for this question.