HARLEY-DAVIDSON’S RR-250 AND RR-350 GP CHAMPIONS

In 1961 Harley-Davidson acquired 50 percent ownership of the Italian motorcycle company Aermacchi. At that time H-D needed modern affordable lightweight motorcycles, the kind of machines that Aermacchi built, in order to attract new young riders to its brand. Badged as Harleys the new Aermacchi lightweights were a welcome success in the US market.

Aermacchi was already actively involved in road racing in Europe and built both factory bikes as well as over-the-counter production racers. Most of these machines were fairly simple air-cooled, four-stroke OHV, longitudinal singles displacing from 125 to 350 cc. These bikes benefitted from having low weight and a low centre of gravity along with a small frontal area. While typically not the most powerful bikes in their displacement classes, they had good low-end torque, fine handling and they loved to rev. Over the decades, competing in both national race series and GP competition, Aermacchi built up an impressive racing record.

In the latter half of the 1960s two-stroke motorcycles, both street bikes and competition machines alike, began to get the upper hand performance-wise when compared to four-stroke rivals. Aermacchi recognized this and by 1967 was competing in the Italian national championships with a prototype air-cooled,

56 mm x 50 mm, 125 cc piston-ported single that developed 20 horsepower at 9,200 rpm. With good early race results the firm began building a small batch of 125 cc production racers for privateers, though many privateers continued to remain loyal to the Ala d’Oro (CRTT in the US) four-stroke singles.

By 1969 Aermacchi’s evolving 125 two-stroke racer, still with a piston-ported engine, weighed only 80 kg (176 lb) and developed 24 hp. It was at this time, with a big push coming from H-D to build something to compete with the ever more dominant 250 and 350 Yamaha twins, that the decision was made to build competitive 250 and 350 cc two-stroke twin-cylinder racers. The 250 cc bikes were to be air-cooled five-speed piston-port twins with the same 56 x 50 mm bore and stroke dimensions of the 125 single. The planned 350 would be an over-bored and longer-stroked version of the 250 with 64 mm x 54 mm dimensions. The new 250 racer, designed by William Soncini, was completed by March 1971. Its engine developed 46 hp at 10,500 rpm, 11 more than the pushrod single that it would replace. Fitted into a double-cradle steel-tube frame, suspended by a Ceriani front fork and Girling rear shocks, rolling on 18inch alloy-rimmed spoked wheels and stopped by a 230 mm 4L4S front drum brake and a smaller 2L2S rear, the bike with full bodywork and fairing weighed the same 113 kg (250 lb) as the old pushrod 250 single. Early testing and race outings on the 250 by new works rider Renzo Pasolini convinced him that it had 250 GP world championship potential. The new 350 cc racer also looked to be promising with about ten more horsepower than the 250.

Much of 1971 was spent developing the bike, but by ‘72 Pasolini and the works team were ready for the 13 race GP season. Only the best seven GP results of each rider were counted for the championship. No less than 48 riders scored points in the 1972 250 GP season. In the end Pasolini lost to Yamaha’s new star Jarno Saarinen by a single point, 94 to 93, despite winning in Italy, Yugoslavia and Spain, plus four second-place finishes. Paso had less success with the 350 ending the season third behind Agostini on the new MV 350 four and Saarinen on his Yamaha.

By 1973 Aermacchi’s works racers were water-cooled, had higher compression and were producing about 50 hp at the rear wheel. That season was meant to be a Saarinen-Pasolini rematch in the 250 championship. That wasn’t to be. In the fourth 250 GP of the season at Monza Pasolini and Saarinen both crashed while dueling for the lead due to oil spilled at the ‘Curva Grande’ during the previous race. Sadly, both men died in what became a 15-rider disaster. Aermacchi’s GP challenge was over, though Paso’s French teammate Michel Rougerie finished the season fifth overall, equal on 45 points with Saarinen who had won the first three GPs.

It was at this point that AMF Harley-Davidson purchased the remaining 50 percent ownership of Aermacchi. Production of their street, off-road and racing motorcycles continued, but as of 1974 were badged as AMF Harley-Davidsons. Dr. Sandro Columbo was tasked with upgrading the RR-250 and 350 racing engines. The revised 250 cc twins employed dual separately removable cranks, had individual water-jacketed cylinder heads and barrels, straight-cut gears, a six-speed gearbox and exposed dry clutch, twin Mikuni or Dell’Orto 34 mm carbs, twin tuned expansion chambers, a Dansi CD ignition and developed 53 hp at the rear wheel at 12,000 rpm, good for 230 km/h (143 mph).

H-D also brought in former Benelli ace Walter Villa as Rougerie’s teammate. Villa’s first of four GP wins on the 250 came in the second round at Imola where he stomped a field full of Yamahas and crossed the finish line 44 seconds ahead of the second-placed Yamaha of Bruno Kneubuhler. With further wins in Holland, Czechoslovakia and Finland, where Rougerie came second, plus a second in Sweden and a sixth in Belgium, Villa’s 77 points (19 more than second-placed Dieter Braun) won H-D their first of what would be three consecutive 250 GP world championships. Michel Rougerie finished ninth overall in the 1974 championship with all other 44 GP points winners that year being Yamaha-mounted.

In the US the RR-250 wasn’t homologated by the AMA until June, just in time for the third AMA 250 GP national of the year at Loudon. H-D works rider Gary Scott stormed to victory in his heat race, then went on to best Yamaha ace Kenny Roberts by 18 seconds for victory in the 50-Mile final, Harley’s first 250 road race win in four years. At July’s fourth round at Laguna Seca it was Roberts who won with Scott chasing him home. At the sixth and final round Robert’s won again with Harley RR-250 riders Ron Pierce and Jim Dunn finishing second and third ahead of 16 other Yamahas.

For the 1975 250 GP season Harley’s works 250s had been further tweaked with a few more horsepower and a top speed of 240 km/h (150 mph). Gone were the big heavy drum brakes replaced by innovative Campagnolo magnesium enclosed-disc hydraulic conical hub brakes. The customer RR-250s employed dual-disc front brakes with Scarab calipers and a 2L2S drum rear.

Once again only a rider’s six best GP results were counted for the 250 championship. The two works Harley-Davidson racers dominated the 1975 series. Villa won in Spain, West Germany, Italy, Holland and Sweden, and came third in Belgium to rack up 85 points and become 250 champion again. Rougerie scored 76 points with wins in Finland and Czechoslovakia, seconds in West Germany, Holland and Belgium, plus thirds in France and

Italy which made him the 250 runner-up overall and 20 points clear of third-placed Yamaha-mounted Dieter Braun. After taking the Constructors 250 cc World Championship for five years in a row Yamaha lost the title in 1975 to Harley-Davidson.

Back in America an abbreviated 1975 AMA 250 cc road race series had begun with Gary Scott racing neck and neck at the front of the field in the Daytona 100 Mile race. In the end he finished second behind Yamaha star Kenny Roberts, but ahead of fellow Yamaha ace Steve Baker as well as 37 other 250 Yamaha racers. Scott followed this up with a sixth at Laguna Seca where Roberts won again, plus a fourth at Ontario Motor Speedway where Baker won.

By 1976 Harley’s works 250 GP twins were developing 58 hp at the rear wheel with a 9,500 to 12,000 rpm powerband and a top speed of 250 km/h (155 mph). Fitted into a double-cradle chrome-moly steel-tube frame with a Ceriani GP fork and DeCarbon twin shocks, the trick Campagnolo brakes with mag wheels, a 24-litre fuel tank and other running gear, including a full fairing, the racers weighed about 105 kg (231 lbs).

Villa again dominated the 250 championship in 1976 with 90 points winning in France, Italy, Holland, Belgium, Finland, Czechoslovakia and West Germany, and finishing second to his new teammate Gianfranco Bonera in the final GP in Spain. Yamaha’s top rider, Takazumi

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Katayama, was the runner-up with 73 points followed by Bonera with 61. Villa also took the 350 GP riders’ crown that year beating his closest rival Yamaha’s Johnny Cecotto 76 points to 65. By then the 347 cc piston-port RR-350 had a 7,000 to 10,800 rpm powerband a developed 68 hp at the rear wheel, good for 266 km/h (165 mph).

Sadly, 1977 would be a turning point for H-D’s RR twins due to financial difficulties at the company. Sponsor funding for the 250 GP team was secured at a reduced level from Nolan Helmets. Villa was joined by new teammate Franco Uncini for what would prove to be a far more challenging season. In addition to the competitive threat posed by Katayama and other top Yamaha riders, Kawasaki and relative newcomer Morbidelli also joined the fray. Despite wins by Villa in Venezuela, Belgium and Finland, and by Uncini in Italy and Czechoslovalia the riders’ title went to Morbidelli’s Mario Lega, while the 250 constructors’ crown went back to Yamaha.

In 1978 H-D parent company AMF sold their Aermacchi operation and its GP team to Italian firm Cagiva who would use it to further develop competitive twostroke racing machines. Uncini switched to a Yamaha for 1978 while Villa’s last podium on an RR-250 was a third at that year’s Dutch TT. Villa also switched to a 250 Yamaha for 1979. IM

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