The Honda Shop Racing team leader faces strong international opposition and local challengers as he sets out to win a third consecutive title in the premier MX1 (450cc) class.

The Papamoa rider confirmed he's back to front-running form following the knee surgery, which curtailed his 2014 Australian Championship campaign.

He won the MX1 class at the NZ Motocross GP at Woodville recently and says getting out of the start gate first in dusty conditions was a key to his GP success.

Suzuki's Rhys Carter (Mt Maunganui) won the Whakatane Summercross title in December and will be a front runner for the MX1 title. Photo / Greg Henderson PhotographyAmong the riders chasing Cooper include Suzuki racers Brad Groombridge (Taupo) and Rhys Carter (Mt Maunganui) along with Yamaha riders Scott Columb (Queenstown) and Ethan Martens (Auckland) and Honda's John Phillips (Rotorua). Rhys Carter (left) won the Whakatane Summercross title in December and will be a front runner for the MX1 title. Photo / Greg Henderson Photography

"My fitness is good and the strength in my leg is improving all the time," said Cooper.

"I'm expecting some close racing and I've been working on making consistent starts because getting a good start is going to be really important.

"New Plymouth has a concrete start pad and I was pretty average at Whakatane (at December's Summercross event), which has a concrete start."

Taranaki Motorcycle Club hosts the opener of the four-round national series at the Barrett Rd track, near New Plymouth, on Sunday.

The defending MX2 champion is Yamaha rider Kayne Lamont (Mangakino).

His preparation was interrupted by a crash at the Whakatane Summercross but was back in action at the Woodville event.

Lamont's main rivals include Honda's Michael Phillips (Rotorua), Micah McGoldrick (Amberley) and Cam Dillon (Taupo) while Suzuki's MX2 bid is headed by Te Puke's Logan Blackburn and Dunedin's Campbell King.

Rotorua's Scotty Canham and Napier's Kieran Scheele are Kawasaki's strongest MX2 riders while Hadleigh Knight (Atiamuri) will ride for Husqvarna.

Two Australian riders are in the MX2 entry list - Jay Wilson (Yamaha) and Luke Arbon (Husqvarna) - while young British rider Rob Holyoake returns for his second Kiwi campaign riding a KTM.

Hamilton teenager Josiah Natzke will be alone in riding two classes - looking to defend his 125cc 2-stroke crown and also chase success in MX2 before heading to a European championship ride.

Natzke's double title bid will be an endurance test but the 16-year-old has prepared by riding in two classes at most of the major events already this summer.

Natzke is a likely front runner in MX2 and a clear favourite for the 125cc title, where his most likely rivals are Yamaha's Courtney Duncan (Palmerston) and Wyatt Chase (Taupo), Honda rider Jacob Steel (Te Awamutu) and Benjamin Broad of Ngatea, who has just switched to a KTM ride.

The Motocross Nationals are raced over four rounds with three races per class at each venue.

By Colin Smith