"I couldn't put a charge on, kind of went backwards so that was disappointing.
"In saying that, I know where I can and should be, so it's a matter of working on my intensity and moving forward from here."
Carter says he's enjoying the switch to the bigger 450cc bike.
"I'm loving it. It requires more strength and control and you can't really hang it out like a 250," he said.
"With my size and weight I'm probably better suited to a 450 and it seems to fit my style well."
The Wonthaggi round saw New Zealand MX1 champion Cody Cooper (Papamoa) return to action for the Penrite Oils Honda team after a month on the sidelines with injury.
Cooper had sustained a fractured cheek bone and eye socket in a qualifying crash at the opening round of the series on March 30.
He qualified second fastest at Wonthaggi behind Matt Moss while his race results were a 12th and fifth, putting him eighth overall for the day.
"The first race was terrible. I got a bad start and then I crashed and I finished 12th," said Cooper.
"The second race was much better. I was third for most of the race but near the end my heart rate spiked ... it was hard. I haven't been able to train properly since the crash."
Cooper now gets a three-week break before the next round.
"The first goal will be to get on the podium in the next couple of rounds and then in the second half of the season the goal is to win some rounds," he said.
The big Kiwi success at Wonthaggi was provided by Mangakino's Kayne Lamont - the New Zealand MX2 champion - who topped the Pro Lites (250cc) class on his Husqvarna.
Lamont had a second and first to take his second overall win of the 2014 series and he is 13 points behind Yamaha's Luke Clout in the championship standings.
Also holding a podium position is Takaka's Hamish Harwood (KTM) who rode to a fourth and a second on Sunday and is two points behind Lamont.
Round four of the 10-round title chase is at Murray Bridge in South Australia on May 18.
