I have a .91 thunder tiger 4-stroke and it has 3 lines....one from tank to carb nipple,one from tank to muffler nipple to pressurize the tank...and has one line coming out the bottom of the engines crankcase nipple that is simply a vent that expels excess oil that I hook a tube to and run out the bottom of my plane.

If your engine is the same setup as mine....I hope this helps...if not,explain more.