What does a diaphragm carburetor lack?

A diaphragm carburetor is designed to regulate the air-fuel mixture for engines, commonly found in small engines such as those in lawn mowers and chainsaws. One of the key features of diaphragm carburetors is that they do not use a float mechanism to manage fuel levels, which is why the correct answer is that a diaphragm carburetor lacks a float.

In a traditional float-type carburetor, the float maintains a consistent fuel level in the float chamber, allowing for precise control of fuel delivery. In contrast, a diaphragm carburetor uses a flexible diaphragm that responds to changes in engine demand and vacuum, which helps regulate fuel flow without the need for a floating device. This design can result in a more compact setup and can be advantageous in applications where space is limited or where a simpler mechanism is desired.

The other components mentioned—secondary orifice, main orifice, and idle orifice—are still present in diaphragm carburetors. These orifices play crucial roles in controlling the mixture at various throttle positions and engine speeds, ensuring that the engine operates efficiently across its range of operation.