To comply with suddenly-announced changes to eligibility rules for the 1970 AMA Grand Nationals, Harley-Davidson had just four and a half months to build a competitive machine that would qualify.
Actually, 200. (100 of which were subsequently destroyed by Harley Davidson, leaving 100 1970 XR750s)
Among the qualifications for entry, was a "homoglation" rule mandating that manufacturers produce a minimum 200 "like" machines to be "available for sale". (Requiring such a quantity of similarly-spec'd motorcycles helps keep the playing field level, preventing construction of balls-out, one-off Goliaths that pulverize all but the most financially-muscular manufacturers.)
The design that would eventually become the most decorated winner in motorcycle history, began life as a highly-modified "Ironhead" Sportster.
The first-year edition of Harley's XR750 series featured many one-offs in appearance, set-up and performance.
All subsequent-year production of complete XR750s, which continued until 1980, were delivered with alloy, rather than iron, heads. Later models also featured "swept" pipes and individual carbs with K & N cone air filters. Frames were also modified, among other more subtle changes.
Though Harley-Davidson produced the required 200 machines, around half were intentionally destroyed by the factory years later. At the time, nobody wanted to buy them. So bean-counters in the accounting department decided it would be better to write them off. Once the victory bell started ringing regularly on the track, sales followed.
This "Ironhead" XR750 is number 057. Until it was recently acquired, the motorcycle has been in the same family since 1973. Though research on the period of 1970-1973 is ongoing, what is known is the bike was owned and raced through the seventies by George Ryan, a contemporary of many of the legends of the day, such as Jay Springsteen - whose "Springer #9 H-D" signature adorns the tail.
