Alan Cathcart rides the 1975 Harley-Davidson RR500, an Aermacchi-based 2-stroke racer.
Top speed: 174mph (280kph)
Engine: 488cc water-cooled reed-valve 2-stroke parallel twin, 72mm x 60mm bore and stroke, 12:1 compression ratio, 89hp @ 10,500rpm (rear wheel)
Weight: 273lb (124kg) with oil/water, no fuel
Fuel capacity: 7.4gal (28ltr)
As a home run two-wheeled Trivial Pursuit question, it has few equals: Forty-one years ago, Harley-Davidson competed in the 1975 500cc World Championship against Suzuki and Yamaha with a race-winning 2-stroke Grand Prix motorcycle of its own design — true or false? Sorry to disillusion the Hog faithful, but however unlikely, it happens to be TRUE!
Yet later that same year, the twin-cylinder 4-carburetor RR500 project died almost as mysteriously as it had been born, leaving Aermacchi, Harley’s Italian division, to focus on retaining its 250cc world crown. The RR500 was the work of a close-knit band of just four men who comprised the Harley-Davidson road racing team, working out of its Italian subsidiary’s lakeside factory at Varese.
Aermacchi became a motorcycle manufacturer in postwar Italy, catering to the need for personal transportation in a war-ravaged country. It did so successfully, and in 1960 Harley-Davidson purchased 50 percent of the company as a source for lightweight motorcycles to be sold in America alongside its Milwaukee-made V-twins. H-D then acquired the remaining 50 percent in 1974. But just four years later, it sold Aermacchi to the Castiglioni brothers, who renamed it Cagiva — only in due course, in 1998, to be rebaptized MV Agusta, which it remains today.
Throughout the 1960s, Aermacchi H-D successfully raced its air-cooled horizontal-cylinder overhead valve singles, sold in the U.S. as the Harley-Davidson Sprint. But in 1971 the Varese-based factory began developing a 2-stroke 250cc twin, after its prodigal son Renzo Pasolini had rejoined Aermacchi from Benelli to race it. In 1972, Pasolini lost the World Championship by a single point to Yamaha-mounted Jarno Saarinen — only for fate to decree that they should both lose their lives in a terrible crash in the 250cc Italian GP at Monza the following May. Pasolini’s vacant seat in the squad, by now a full Harley-Davidson team, was taken by the up and coming Gianfranco Bonera, and as Albino Fabris, one of the four men together with Ezio Mascheroni, Claudio Lazzati and ex-racer Gilberto Milani making up the Harley Grand Prix team’s engineering crew recalls, it was thanks to him that the RR500 project came about.
Order the January/February 2016 issue of Motorcycle Classics to read more about the 1975 Harley-Davidson RR500. Contact Customer Service at (800) 880-7567 or contact us by email.