Plug in that Harley, boy, or fill this one up with biodiesel, we're going for a ride. Alternative fuel Harley-Davidson motorcycles - both electric and biodiesel - are profiled in this piece from the Milwaukee State Journal. The bikes are homemade modifications, not official prototypes, but they're certainly green.
Harold Benich's biodiesel Harley-Davidson Fat Boy can get up to 115 mpg, and regularly gets 80 to 90 mpg .