"It is the nature of my racing career that I have not been in New Zealand to tackle the nationals for so many years," the former world champion said.
"I didn't know what to expect. This is a great build-up for me to return to the international stage."
His next outing is expected to be at round one of the Australian Motocross Championships, north of Brisbane, on April 1.
Motueka's Josh Coppins finished overall runner-up to Townley in the motocross championships, while Cooper settled for third.
Bel Ray Honda team riders Justin McDonald, of Christchurch, and Michael Phillips, of Rotorua, finished the championships ranked fourth and fifth respectively, while Auckland's Hamish Dobbyn and Taupo's Brad Groombridge made it five Honda riders in the top seven in the MX1 class this season.
Meanwhile, Taupo's Bel Ray Huka Honda star Cameron Dillon also stood out on Sunday; the teenager finishing the day runner-up in the MX2 (250cc) class to eventual champion Darryll King, of Hamilton.
"Cameron crashed heavily during the supercross nationals and, although we had planned on him making a comeback during the motocross nationals and riding today at Taupo, he surprised a few people," said Bel Ray Honda tram manager Peter Finlay.
"He was on fire today and certainly finished on a high."