Perry VP-30 Regulating Pump (glow Fuel)This pump is constructed so that it draws fuel from the tank, passes it through a precision regulator section, then to the carburettor. Correct pressure to the carburettor is adjusted by the Hex regulator adjustment screw on the plastic end of the pump. To increase fuel flow the screw is turned in, to decrease turn the screw out. The pump is energized by engine crankcase pressure. The built in regulator supplies fuel to your engine with no variation