The American Flat Track Series, formerly known as the AMA Grand National Championship and the AMA Pro Flat Track Series, is an American motorcycle racing series. The race series, founded and sanctioned by the American Motorcyclist Association (AMA) in 1954, originally encompassed five distinct forms of competitions including; mile dirt track races, half-mile, short-track, TT steeplechase and road races. The championship was the premier motorcycle racing series in the United States from the 1950s up until the late 1970s when, supercross events held in easily accessible major league stadiums became more popular.
In 1932, the AMA sanctioned a racing class called the Class A Dirt Track championship allowing for motorcycle manufacturers to enter prototype machinery. In 1937, the AMA introduced a new class called Class C which featured street-legal motorcycles in an effort to make motorcycle racing less expensive for ordinary motorcyclists. When manufacturers cutback on racing budgets during the Great Depression, it spelled the end of Class A competition and, the Class C championship became the most important championship. In the years prior to World War II, the Class C championship helped fuel an intense rivalry between Harley-Davidson and Indian, the two major American manufacturers of the period. During the Second World War, there were no championships held between 1942 and 1945.
From 1946 to 1953, the AMA Grand National Champion was crowned based on the results of a single race, the Springfield Mile held at the Illinois State Fairgrounds Racetrack. Side-valve engines had a maximum displacement of 750cc, while overhead valve engines were limited to 500cc. In 1954, the Grand National Championship series was introduced featuring four different types of competitions: three of the competitions (Mile, Half-mile, TT) were held on dirt tracks, while the fourth was held on asphalt paved courses. With the demise of the Indian motorcycle company in 1953, the Harley-Davidson factory was left to dominate the series. Harley-Davidson rider Joe Leonard won the first Grand National Championship in 1954 and won the title two more times before moving on to a career in auto racing. Carroll Resweber became the first four-time champion, winning four consecutive championships for Harley-Davidson from 1958 to 1961. Since 1961 short-track events became part of the Championship; those races had a 250cc displacement limit. In the 1960s, British manufacturers seeking to bolster sales in the burgeoning American motorcycle market, began to compete in the championship. Dick Mann won the national title for BSA in 1963, marking the first victory for a foreign manufacturer. Triumph would win three Grand National championships in four years with Gary Nixon winning back-to-back titles in 1967 and 1968, and Gene Romero taking another title in 1970. New regulations for 1969 eliminated the displacement penalty for overhead valve engines; in dirt track events brakes were permitted for the first time. Mann would win a second crown for BSA in 1971 before the British motorcycle industry collapsed in the face of stiff technological competition from Japanese manufacturers. In 1973, Yamaha's Kenny Roberts would win the first Grand National championship for a Japanese company. Since 1973 the displacement limit for short-track events was increased to 360cc, but multi-cylinder two-stroke engines were still limited to 250cc.
In 1975 the championship gained full sponsorship from R.J. Reynolds Tobacco and became known as Camel Pro Series. Between 1979 and 1982 the series was named Winston Pro Series, reverting to Camel brand in 1983.
In 1976 dirt track engines were limited to a maximum of two cylinders; in 1977 the short track engines were limited to 250cc and limited to one cylinder. When the Yamaha team withdrew from the Grand National championship after the 1977 season, Harley-Davidson was left once again to dominate the series. By 1983, the Grand National Championship had become the best attended form of dirt track racing in America, either on two wheels or four wheels. This would be the high point for the championship as, other forms of motorcycle racing such as motocross and road racing began to overtake dirt tracking in popularity. In 1984, Honda entered the championship and broke the Harley-Davidson stranglehold with Ricky Graham winning the championship. Honda followed with three consecutive national championships by Bubba Shobert before they withdrew in 1987, leaving Harley-Davidson once again as the sole major manufacturer in the series. In 1984 short-track rules granted a 500cc displacement limit for four-stroke engines.
In the 1970s and on into the 1980s, the Grand National Championship proved to be a fertile training ground for world champion road racers as, AMA dirt track racers such as Kenny Roberts, Freddie Spencer, Eddie Lawson and Wayne Rainey all went on to win the 500cc road racing world championship. The motorcycle road racing technology of the late 1970s featured engines with power in excess of what the frames and tires of the day could handle. The resulting tire spin created a style of riding more reminiscent of dirt track riding, where sliding the rear tire to one side is used as a method to steer the motorcycle around a corner. This proved to be a great advantage to American dirt track racers who were accustomed to sliding their motorcycles. As Grand Prix motorcycle racing evolved into its current MotoGP formula with electronic traction control limiting rear wheel sliding, the advantage once held by former dirt trackers has been diminished.
After the departure of the Honda team in 1987, the Harley-Davidson factory racing team dominated the series with rider Scott Parker winning nine national championships within an eleven-year period. During this period, dirt track racing continued its decline, partly due to the fact that motocross and road racing motorcycles could be purchased directly from the manufacturers, whereas dirt track racers had to be hand-built.
In 1986, the AMA recognized the changing nature of motorcycle racing by making the Grand National Championship into a dirt-track-only series; road-racing rounds were branched off into a separate championship which eventually became the AMA Superbike Championship. In that season Camel sanctioned both series which were named Camel Pro Dirt Track Series and Camel Pro Road Racing Series.
In 1987 and 1988 the sponsorship strategy changed again and the Camel Pro Series name referred to a particular series based on selected rounds from both Grand National and Superbike championships.
New rules for 1987 banned two-stroke engines from dirt track races; single cylinder engines had a maximum displacement of 600cc, while twin-cylinder had a 750cc limit. Since 1989 only twin-cylinder engines were allowed in mile and half-mile events. Since 1989 the Camel Pro Series reverted as title sponsor for the Grand National Championship; the sponsorship lasted until the end of 1992 season. New dirt track classes were also introduced designed to attract young riders to the sport and, new rules for machinery were adopted in an effort to make it easier for motorcyclists to compete with motorcycles readily available from manufacturers. While the Grand National Championship is no longer the premier racing series in the United States, it continues to have a loyal following.
In 2002 the single cylinder engines were limited to 550cc (push-rod) or 505cc (OHC); the twin-cylinder class was expanded to include production-derived engines up to 1250cc.
In 2006 the Grand National Championship was split into two separate series: Grand National Championship Singles (for short track and TT events) and Grand National Championship Twins (for half mile and mile events); no overall title was awarded, although in 2007 there was a de facto champion by virtue of winning both championships. Single-cylinder engines were limited to 450cc.
Since 2010 the Grand National Champion title is reinstated and awarded to the rider who scores the most combined points.
For 2017, the American Flat Track Championship, the new name for the Grand National, will also change the classification of motorcycles, logo, race format, and rules. The primary change will feature the twin-cylinder motorcycles (650-999cc) in the top class, while the second-tier class will be for single-cylinder motorcycles (450cc). NBCSN will air the championship tape-delayed on Thursday nights.