I hadn't realised that it was that early, the bike came to me free of charge via a post on the old (and much missed) Thumper Page forum, it had broken its engine and the whole bike was free to whoever claimed it first. I set off to Southend in the car with a borrowed trailer and SimonM and I picked it up from the very pleasant owner.
The bike had been converted to run using a bloody huge Bing carb from a BMW twin, but I never got to fit a running engine to it and so can't report how it ran.
The engine came from a bike also bought in Essex by my brother. His partner Liz ran it for a while until he finished building her lovely Blue XBR, at which point the second bike came to me.
The exhausts that I gave you came from my very first (brand new) XBR, bought in 1987.
Good luck with the old banger.
GC