Simon, I have a Mystic and a 1971 R750/5. I just went out and pulled the crash bars off the 750, and they fit perfectly on the Mystic. I donĀ“t know if my bars are factory or aftermarket, but the frame dimensions and mounting points are apparently the same for a lot if years, so it would be pretty tough to go wrong. Mine clamp to the downtube on top, and bolt to the engine mount underneath.