The Wellingtonian made it a trifecta in the third race over 18 laps, although the winning margin was shortened as he only beat Walker by 6.993s on that occasion, while Wiki finished a lap down.
For the Supersport 600c, Rangiora's Avalon Biddle won the first two races while Te Awamutu's David Hall won the third race after coming third and second behind Biddle in the previous two.
Series leader Toby Summers, from Manukau, came second to Biddle in the first race, but then crashed twice, therefore falling 29 points behind Biddle in the overall season points tally.
The series concludes in Taupo this coming weekend.
Other class leaders after round four of the series are Glen Eden's Daniel Mettam (Superbikes); Palmerston North's Jacob Stroud (Supersport 300 class); Papamoa's Leon Jacobs (250 Production class); Jacob Stroud (Superlites); Whangamata's Ben Rosendaal (650 Pro Twins, provisional); Australia's Yanni Shaw (125 GP); Hamilton's Jesse Stroud (Gixxer Cup) and Christchurch's Dennis Charlett and Will Clim (sidecars).