Born in Sunnyside, Washington, Pomeroy's family relocated to Yakima, Washington shortly after he was born. His father owned a motorcycle shop that had employed Evel Knievel before he became a famous daredevil stunt rider. Pomeroy began to race professionally in Canada to circumvent the American Motorcyclist Association's 18-year-old age restriction and ended up winning the Western Canadian Championship. He made his AMA debut in 1970 and posted a sixth-place finish in the support race of the 1970 Trans-AMA motocross series round in Washington.