Simple test.Only effective when it's really bad though.Open the gas cap.Listen at filler.Turn on ignition.As the pump primes you'll hear fuel spraying all over the inside of the tank.If it's very bad you'll see it.Harley can't do anything for you until it's broken at this point.
Just tried this. No noises when ignition turned on. Noise for about 2 seconds when switch flipped to "RUN." Then silence. Seems like it passed the test for now. One further question - my tank was just about full, will this test be more effective with the tank almost empty to hear if any fuel is spraying and hitting the side of the tank?