Yes looking from the front of the engine the line closest to the exhaust is fuel supply and the one away from the exhaust side of the engine is not Vent but is the Pressure line back to the tank.
Go here For a diagram and manual that came with the engine.
http://www.yspartsandservice.com/pdf/FZ110.pdf
There is a check valve in the pressure line that allows pressure to flow from the engine to the tank...but not from the tank back to the engine.
Take special care to notice this check valve. It has to be there.
Troy Newman
Team YS Performance