TRX350FM 2004 leaking gas not sure how to fix. Leaking from black tube coming out of the bottom of this part.

 

Easy fix, turn tap off, run bike until it stalls from lack of fuel. Turn tap on, if the fault is a bit of dirt stuck between float needle and seat, the rush of fuel on the wide open needle may shift the dirt. If that doesn't work, remove float bowl and clean needle and seat by hand, checking the tiny plunger inside the needle is springing up and down freely, any sticking of that and you need a new needle. Never ever lift the pipe upwards to stop fuel from running out, you will then fill the airbox and sump with fuel. Just turn the tap off. If cleaning the needle fixes it for a while, then it does it again, you may need either an in line filter, or to clean the tank out.