2001-2002 Yamaha 50HP F50Z/T50Z Ouboard 4-stroke engines service manual, Page 19Get this manual
Technical tips Operation When the throttle is opened suddenly, diaphragm (via the link that is connected to the throttle lever) operates to pressurize the air in the pump chamberThe pressurized air opens diaphragm 2, and becomes distributed to the carburetors by passing through the pipes that are connected to the carburetorsThe pressurized and distributed air then utilizes the passage of the main air jet to flow into the main nozzleThe pressure of the air helps suck fuel from the main jet, which increases the fuel in the main nozzle, and thus achieves the fuel enrichment