Air-vent system for a carburetor

Claim 1

A vent system for a float chamber of a carburetor comprising a carburetor housing portion defining a float chamber therein, a vent port provided in said housing portion, a fuel vapour absorptive vessel-like charcoal cannister having inlet and outlet ports, a control valve having inlet and outlet ports, a first passage means which connects said vent port to said inlet port of said control valve, a second passage means which connects said outlet port of said control valve to said inlet port of said fuel vapour adsorptive vessel, and an air pump provided with a delivery port and driven by an associated engine which operates with said carburetor, said control valve defining a through passage therein which connects said inlet and outlet ports thereof and having a valve element which selectively tranverses said through passage to substantially intercept said through passage, an air chamber means which is connected with the delivery port of said air pump and biases said valve element to traverse and close said through passage when it is supplied with air pressure above a predetermined level, and a spring means which biases said valve element toward an open position to counter-act said air chamber means.