Be sure the flex line is in good condition first, or just swap it out for a new piece of fuel line. They can weather-crack and suck air without leaking fuel to the outside. A piece of new hose won't break the bank. There's probably another flex line where the frame-mounted steel line meets the tank. I like to use a vacuum gauge to check for good fuel pump operation, and seep leaks in flex lines. Disconnect the fuel line, plug in the gauge, and idle the engine. It should run for a while on the gas in the carburetor bowl. Back at the tank outlet, there should still be a good vacuum with the engine running, 12 inches of mercury or more. If you've got good vacuum that stays put for a few seconds after the engine stops, look inside the tank for problems.
Jerry
