In contrast, Dibben won five races, but failed to finish the second race at the series opener at Taupo because of mechanical failure and this is what torpedoed his campaign.
"Although I had a solid 12-point advantage at the top of the standings when the day started at Whanganui, I still felt that I was under a bit of pressure," said Hart.
"Whanganui rider Ben Dowman was giving me quite a hard time in the battle for second place and I didn't want to be dropped back behind him.
"Dibben was long gone at the front and so it was just a matter of me staying out of trouble and banking the points for second place.
"This is the third year in a row that I've won the super moto class and it's been on the same 2013-model Yamaha YZ450F.
"It's been a well-maintained bike and gets freshened up each year, but it has always run like clockwork and never misses a beat."
Meanwhile, Wainuiomata's 600cc supersport class rider Shane Richardson is looking to keep his Whanganui momentum going when the four round NZ Superbike Championships get underway at Canterbury's Mike Pero Motorsport Park next weekend.
Glen Eden's Daniel Mettam may be defending national 600cc supersport champion and Whakatane's Damon Rees may have wrapped up the 600cc title in the Suzuki Series, doing just enough around Cemetery Circuit to get the job done, but neither rider can afford to rest on their laurels.
Richardson won the final round in this class on Whanganui's streets after he qualified his Kawasaki Ninja ZX6R fastest and gained a valuable point for pole position.
He then finished 1-2 in the two races proper, to win the day, although Rees twice finished third - behind Richardson and Lower Hutt's Jay Lawrence - and this was sufficent to take the F2/600cc crown by four points from Richardson, with Wellington's Rogan Chandler claiming third overall.
"It was a good day for me. This is the first time I don't have to fix the bike before going to the South Island for the first round of the nationals," said Richardson, refering to his crash on Boxing Day last year.
"I had no incidents at Whanganui this time around.
"I arrived at Whanganui 12 points behind Rees and, in the end, he only won the series from me by four points.
"If I had managed to win that last race at Whanganui [runner-up to Lawrence], then I would have been beaten by Rees for the series by just one point.
"If Rees had finished fourth in that race [instead of third], then I would have won the series. That's how tight it was."
"But it's always nice to start the nationals with confidence and I have that after winning the day at Whanganui."