Evaporative emissions control for carburetors

Abstract

An evaporative emissions control system for carburetors used in the internal combustion engines of vehicles, such as motorcycles, has an evaporative emissions control valve attached to the carburetor in the air intake path to the carburetor. The evaporative emissions control valve may be implemented as a sub-assembly add-on or as an integral part of a carburetor or back plate. The evaporative emissions control valve includes a valve, such as a rotatable plate valve, which may be electrically operated by an electrical actuator, such as a dual-wound solenoid actuator. At engine start-up, when the vehicle ignition switch and starter switch are both closed, both windings of the solenoid actuator are energized to provide a strong opening force for the evaporative emission control valve. During steady-state running of the engine, only a single solenoid winding is energized by the power provided through the ignition switch, to maintain the evaporative emissions control valve in the open position. When the ignition switch is opened and the engine is turned off, the evaporative emissions control valve is closed to prevent the release of fuel vapors from the carburetor. A vacuum controlled switch may be used to delay closing of the evaporative emissions control valve after the ignition is turned off for a sufficient time to prevent fuel pooling in the carburetor. A passage may be provided in a shaft of the control valve to selectively control venting of the carburetor fuel bowl, opening the vent during engine operation while closing the fuel bowl vent to prevent evaporative emissions therefrom when the engine is not in operation.