Two names came to mind when you asked this question.. Cal Rayborn and Leo Payne..
"Cal Rayborn rode to a record in 1970 by piloting a Harley-Davidson Sportster-based streamliner to a new American and International record of 265.492 MPH. The 'Manning' Harley-Davidson, to which it was referred, weighs more than 700 pounds and is more than 10 feet long."
Cal was more of a road racer out of San Diego and raced with Don Vesco. He was killed in 1973 at the age of 33 while racing.
Leo Payne's highly modified 1957 Harley-Davidson Sportster, dubbed the 'Turnip Eater', was the first machine to exceed the 200 mph mark. Payne's 1969 Bonneville Salt Flats performance helped kick-start S&S Cycle's successful line of racing carburetors. Payne was inducted into the AMA Motorcycle Hall of Fame Museum in 1991 alongside Joe Parkhurst, Founder/Publisher of Cycle World magazine.
Leo was an excellent engine builder and master at modifying and tuning gas and fuel carburetors. Once he began modifying his Sportsters, Leo quickly earned the reputation of having two of the fastest Harleys in the Midwest, turning 11.08s at 125 mph on Turnip Eater and mid-9s at 150 mph on his fueler. Turnip Eater started life as a '57 Sportster, and Leo purportedly coined the bike for eating up British imports on the dragstrip.
Leo Payne's '57 HD - The Jockey Journal Board
Payne died from cancer on September 18, 1991.
Marv Jorgenson's 96ci AA/Dragster in the Atco pits. Marv's Sportster engine was very large for the times, and was one of the first Harley gassers to break into the 9s. (Circa 10/26/69)
Here is a link to pictures and history of Ironhead racing (read first)
Harley Davidson's Golden Age Of Racing - Hot Bike Magazine Leo Payne - Motorcycle Hall of Fame
And last but not least Bonnie Truett... he was asked
How and why did you get into racing?
“I had a happy throttle hand and always rode hell-bent for leather. I was getting way too many tickets riding on the street, and I just decided that it would be cheaper to do my racing on the racetrack.
“I started out T.T. racing in the early ‘60’s. I liked T.T. because, with the cutbacks and everything, a good rider could usually make it up on riders with more horsepower. I raced a K Model until someone stole it.
“I started drag racing in 1962 and switched to fuel in 1965 or ’66. I went in the 11’s and then the 10’s…I still remember my first nine-second race. It was a 9.99 in Dallas.
“Back then, we were all using those little four inch Avon slicks and no wheelie bars. The theory was that the faster you could spin the tire, the faster you would go. Leo Payne changed that when he accidentally invented the slipper clutch at Irwindale in 1967 or 1968.
“His clutch slipped when he left the line, but then the heat from the friction welded everything together when he was about halfway down the track. The clutch locked up solid, and Leo made the fastest run he’d ever made. The slipper clutch was a big deal because it let us go to a bigger tire. Without the slipper, you’d bog the big tires.”
Truett & Osborn
Some great stuff in these articles.
Jim
World's Fastest Ironhead? 
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