Gas Tank Check Valve?

[BigGreenMachine]

My tank does not have it and I refuse to run the tube from the cap. How do you make these little check valves?

http://cgi.ebay.com/ebaymotors/Gas-Tank-Vent-Valve-Black_W0QQitemZ4628341541QQcategoryZ43971QQssPageN ameZWD1VQQrdZ1QQcmdZViewItem

[jason 32]

bye one leave the hose off

[BigGreenMachine]

Got one on the way thx.