Groombridge won the MX1 class at the Auckland Motocross Championships at the same track last November and can be expected to come on strong on Sunday.
In the MX2 (250cc) class Mangakino's Kayne Lamont (Husqvarna) has so far proved himself the man to beat.
The 20-year-old Kiwi international enjoys a solid 27-point advantage over his nearest challenger, Dargaville's Hamish Dobbyn (KTM), with defending MX2 champion Scott Columb (Yamaha), of Queenstown, in third spot overall.
Momentum is on Lamont's side. He has won three of the six races in this class so far, and finished runner-up in the other three.
In the 125cc class, Te Puke's pre-season favourite Logan Blackburn (Yamaha) suffered a nightmare run at Tokoroa, but will be looking to bounce back at Pukekohe on Sunday.
Misfortune at Tokoroa dropped Blackburn from first to third in the 125cc standings, while Hamilton's Josiah Natzke (KTM) and Atiamuri's Hadleigh Knight (KTM) shared wins at Tokoroa to move up to the top two spots.
Though only 15, Natzke, at No1, has shown maturity beyond his years and he is a respectable 20 points ahead of Knight.
Blackburn is 15 points further back and will need a miracle ride at Pukekohe on Sunday if he is to burst back into one of the top two positions.
Tauranga's Aaron Wiltshier (KTM) will also be worth watching. Wiltshier had been second in the 125cc standings after round one and had finished runner-up to Natzke in the day's first race at Tokoroa, but unfortunately he crashed in the next race and did not return to the track.
The BikesportNZ.com rider vows to be on the starting line again at Pukekohe.
Pukekohe Motorcycle Club riders James Ainsworth, Shaun O'Connor, Daniel McNeil, Van Major, Joel Trappitt, Simon McCarthy, Kurtis Lilly, Sam Greenslade, Robbie Bolton, Dean Collins and Jayden Turnwald are among the best from their region and each of these riders has high hopes of moving up the series rankings in their respective classes on Sunday.
The championships wind up with the fourth and final round set for Taupo on March 22.