In 1972 he competed in the inaugural AMA Motocross National Championship. He won the season opening 250cc race at Saddleback Park in California before, switching to the 500cc class where he finished the 1972 season in fifth place overall. His performance earned him Bultaco factory support through a local Bultaco concession. He was offered the opportunity to compete in a few select world championship Grand Prix events in Europe and he readily accepted. At the end of the 1972 season, Pomeroy along with Brad Lackey, Jimmy Weinert and Gary Jones were selected by the AMA to be the first-ever team to represent the United States at the Motocross des Nations where the team posted a seventh place result.