2012 Harley-Davidson Forty-Eight - XL1200X, First appearing on a Harley-Davidson motorcycle back in 1948and providing the inspiration for the Forty-Eight model namethe small 2.1 gallon tapered peanut fuel tank holds strong today with its traditional styling and modern attitude. A low, powerful bulldog look that gives way for showcasing more engine, the peanut fuel tank is attitude and looks all balled up into one.