I've got a '05 ultra classic with 22k miles. Lately I"ve been smelling gas while sitting on it just before I start it. I can't find any leaks and it doesn't happen all the time. It doesn't matter how much gas is in the tank: full, half, or nearly empty. No wind, or slight breeze. Hot temperature, or cool temperature. Bike been sitting for hours or minutes. I don't smell it while riding or stopped for signal lights, or just before I turn it off. Any ideas?