Consistent riding from Christchurch's Justin McDonald was sufficient to see him take the crown instead.

Unfortunately for Cooper, his total dominance of the class at rounds three and four could not undo the damage caused by the injury-plagued early phase of his campaign.

The MotoGB-supported rider had to cope with serious hand and face injuries at round one in Timaru and round two in Rotorua respectively and he even found himself on the receiving end of a rock in New Plymouth on Sunday.

"I could barely see out of my right eye in that last race," said Cooper.

"I got a rock in the face from the rear wheel of a lapped rider and everything was blurry," he explained.

But, despite that handicap, Cooper was in stellar form at the weekend.

The Suzuki star romped to yet another hat-trick of convincing wins in the glamour MX1 class, taking his fuel-injected RM-Z450 to the front early in each race at the muddy Taranaki track, and then steadily building his advantage from there, each time finishing well ahead of McDonald.

"The bike was awesome," said Cooper afterwards. "I raced one of these in America in 2008 and absolutely loved it then too (when he finished fifth in the high-profile US national championships). The bike turns so well and has so much power, it's unbelievable.

"I proved I was the fastest guy out there this year but I had a little bit of bad luck."

Fellow Suzuki rider Brad Groombridge, of Taupo, moved up to third in the MX1 championship. Groombridge finished 3-5-3 in his three outings on Sunday, giving him a podium result in his first season in the big bike class.

In the MX2 class, the battle continued at Taranaki between Kiwi internationals Michael Phillips, of Rotorua, and Queenstown’s Scott Columb.

The pair had been level-pegging throughout the series but Phillips’ 5-1-2 results gave him the points he needed to take the title.

Suzuki's Columb, who had been racing the bigger RM-Z450 in Europe earlier this season, took a stock standard fuel-injected RM-Z250 to 8-2-1 results on Sunday, sealing the runner-up ranking for this season. 

In the fight for under-21 honours in the 125cc class, Waitakere's Ethan Martens won the title ahead of Wanganui Suzuki star Tom Managh.

Managh (RM125) had been running third in the class but came on strong at New Plymouth to surge up the standings.

Managh finished 3-3-4 on Sunday to finish the championship 62 points behind Martens.