Dumb question and I confess ignorance on the subject, but was there any harley xr's running in those days?
Gene Church rode this XR based Harley Owners Group sponsored Tilly tuned hammer @ Laconia 6/84 battle of the twins.
#31 in the lead should be Cook Neilson on The California Hot Rod, or Old Blue, depending on who's telling the story :) #21, don't know of the top of my head. It's a BMW though. #163 is probably Reg Pridmore. Unless that's #63, then it's Steve McLaughlin. But the helmet and leathers look like Reg. I don't know that one. Dr John?
If you remember how those guys put that bike together, and the fact that Cook Nielson had almost no road racing experience (he had been a drag racer before that), I would have said underdog - that they did as well as they did is a miracle. The engine was built with help from a lot of Cook's drag racing POCs - not from high tech stuff from Italy.