This is a beast with a convoluted history. It’s one of just three racing RR1000s produced by Erik Buell before the road version was released in the late 80s. The story starts with the Harley Owners Group, which asked Buell to make a chassis for
a race bike using the Harley-Davidson XR engine: the rise in engine capacity from 750 to 1000cc for AMA BoTT racing had made the XR750 uncompetitive against most European high-performance motorcycles. So Buell designed an XR1000-powered bike with racing in
mind. It appeared in 1986 and was known as “Lucifer’s Hammer II”, or more formally, the RR1000.
Full story: Buell RR1000R | Bike EXIF