That is a gravity feed setup, and it shouldn't be that way.
The engine will run if you fill the fuel tank up full, so that the liquid level is higher than the carburetor. As it burns the fuel, it might siphon enough out of the tank to keep running. I have seen it happen but the right conditions have to be there. You will loose power since it will be running lean.
You really need to put on a fuel pump, the block off plate is there below the carburetor. Your engine will not run right until you do. I sell the right replacement fuel pump kits for $65 apiece.