It looks as if the fuel tank has had water in it, from the brown sludge in the well that the main jet screen dips into. The main jet is right behind that screen, either in the bottom of the tower or in the side of it near the bottom. Clean that jet and the passages behind it with carburetor cleaner, and inspect it afterward to be sure it is clear. Was the well below the main jet screen full when you removed the carburetor from the tank? The purpose of the fuel pump is to keep that well steadily overflowing back into the tank. The pattern of the crud on the filter suggests it may have been barely reaching down to the fuel in the well, which would imply a fuel pump malfunction. Are you sure the tube that leads to the fuel pump intake screen (the longer tube, with the screen that was only slightly fouled) is clear? I suggest you revisit the fuel pump overhaul you did earlier, and make sure all is well there.
