Cooper finished the day in Taranaki with a 2-1-1 scorecard, enough to give him a three-point edge over his nearest threat, defending champion Kirk Gibbs.
Australian visitor Gibbs registered a 1-2-2 scorecard to settle for the runner-up position, while Mangakino's Kayne Lamont chimed in with three third placings and took the third step on the MX1 podium, nine points adrift of Gibbs.
Cooper is a six-time former New Zealand MX1 champion and did not take kindly to losing his crown to Gibbs last season, something he is determined to rectify this year.
"The first race was frustrating because I just couldn't find a way past Kirk. Well, I actually did get past him at one stage, but then I went off a jump sideways and lost that position again. I was probably a little bit too relaxed here," Cooper said.
"I was trying to tippy-toe around the track today, to not make any mistakes. There are parts of this Taranaki track where you can be pushing and feel good and then suddenly it all lets go.
"As long as I was in the hunt for the title when I left here today, I would be happy and I'm actually leading the way, so that's even better."
Round two of the New Zealand Motocross Championships is set for Rotorua in just two weeks' time, on February 17. Round three follows, at Pukekohe, on February 24 and, finally, the nationals wrap up at Taupō on March 10.
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