Those water cooled heads were badly needed due to the massive heat generated from running a lean enough mixture to meet current emissions standards. I heard that the rear cylinder ran so hot that the NHTSA was investigating complaints about burns on the legs of passengers, and H-D compensated for the heat by deactivating the rear cylinder when idling.Originally Posted by Az Wingrider
The F6B's twin side radiator design handles heat better than any motorcycle I've owned. The way the heat exits on the sides keeps much of it off of your legs. It was a challenge for the stylists to work with those radiators. The fins don't look bad on GL1800s, but on the 1800 Valkyries the radiators gave the bike a strange appearance and surely didn't help it sell.
