As engine speed increases, air velocity through the venturi causes a vacuum (low pressure area) in the venturi. Fuel then begins to flow from the fuel bowl through the main jet and into the main well where it is mixed with air. Air supplied through the high speed air bleeds, mixes with the fuel through small holes in the side of the main well tube. The air-fuel mixture moves from the main well tube to the main nozzle where it is discharged into the venturi.