Pete, I did the little speriment a couple of days ago. I used the .65 with a TurboHeader and an IronBay regulator. Holding my finger over the exhaust out and flipping it would pressurize the tank and make nice whoosh when unplugging the vent line. I could not get the fuel to the tank unless I choked the carb. A starter would bring the fuel to the carb in about 2 seconds. I used the Cline duck bill check valve. All others except Hobby Lobby metal ones melt on a four stroke.