One line, directly under the fuel cap, is a water drain or spill drain. If you open the cap, you should see a drain hole. So things like rain water drain from around the cap, through a tube that goes completely through the tank, and comes out under the tank. It normally just goes to a hose to the ground.
The tube toward the front, extends way up high in the tank. If you over fill the tank, gasoline will drain out that. Or as the temperature changes, fumes can vent out that. It normally goes to a tip over valve to prevent gasoline from pouring out if the bike falls over. That then normally goes to the charcoal tank to keep the fumes from stinking up the garage.
So normally, they are separate systems.
