Float bowl style carburetors require float bowl venting to work properly, just ask anyone who has ever had plugged or frozen vent lines. The Lectron, like more conventional carbs, vents its float bowl through external vent/overflow hoses that hang down in front of the rear wheel. The SmartCarb vents its float bowl quite differently – from inside the airbox via a scoop/port located in the top of the venturi bell.
This patented internal venting feature allows the SmartCarb to compensate for a much wider range of air densities compared to the externally vented Lectron.
Venting and airflow communication between the airbox and the float bowl applies a steady, equalized pressure against the fuel in the bowl that is proportional to air velocity and density inside of the airbox. Put simply, more dense, heavier air drives more fuel flow, less dense air drives less fuel flow, and air/fuel ratios stay consistent regardless of elevation or temperature changes.
Beyond better air density compensation, internal venting also provides for sufficient top end fueling in the SmartCarb without the need for a power jet. Although the original Lectron of 1974 did not have a power jet, all modern iterations of the design come with at least one or more power jets to provide enough fuel to the mix from mid to top.