The sport of motocross experienced explosive growth in 1973 and motorcycle manufacturers sought to capitalize on the expanding market with all four Japanese manufacturers fielding factory-backed teams alongside their European counterparts.[1] Pierre Karsmakers from the Netherlands dominated the 1973 500cc national championship, winning seven of 12 AMA Nationals and claimed 17 victories in 36 races overall.[1][2] Karsmakers is credited with helping raise the level of American motocross by stressing the importance of physical fitness and machine preparation.[2] 1973 marked a turning point in American motocross when Jimmy Weinert became the first American rider to defeat the then-dominant European riders in the Trans-AMA Motocross Series at Lake Whitney Ranch in Texas.[1][3] His victory showed that the level of American motocross had begun to compare with the level of European motocross.[3]
As in the 1973 season, after the season-ending 500cc race on September 9, American riders competing for the AMA national championship continued to accumulate points counting towards the national championship while they competed in the 1973 Trans-AMA motocross series which began on September 23rd and hosted visiting European riders from the Motocross World Championship.[1] Although Karsmakers was a Dutch citizen, he was competing under an AMA license so, he was listed as the "Top American" finisher in the Trans-AMA series.
After winning the 1972 250cc national championship on a Yamaha, Gary Jones was hired by Honda to help develop their new Honda CR250M motocross bike for the 1973 season.[1][4] He did so successfully to win his second consecutive 250cc national title.[1]
Pierre Karsmakers
Mike Hartwig