Honda GX340, GX390 carburetor stud bolt

Venturi is a narrow passage, pipe, hose, or conduit that restricts airflow. That restriction forces air to speed up and drop in pressure. That low pressure vacuum zone is required for suction. In a carburetor, that suction draws in fuel. It also atomizes the fuel and sends it to combustion.

1. mixes air and fuel in the right ratio for an internal combustion engine to run,
2. controls engine speed by regulating airflow through a narrow section (venturi).