His father Richard said the weather was an ''absolute disaster'' and the unavailability of wet tyres meant Josh (10) was unable to get past the heats in the cadet class.
He was one of nine Kiwi karters attending the five-day meeting, the biggest annual kart event on the global calendar, with more than 600 drivers entered.
Mr Bethune said rain began on the Wednesday when practice started and although they had been told wet tyres would be available to buy, they were not.
KartSport New Zealand spokesman Ross MacKay said at previous SuperNationals meetings the searing desert heat had been the issue, which was one of the reasons few teams had enough wet-weather tyres to go around: 96 competitors were not allocated any.
A year 6 Wakari Primary School pupil, Josh borrowed two sets of wets on Saturday to compete in the last-chance race to move forward from the heats but despite surging through the field from 40th to 15th, he was forced to retire when another competitor crashed into him.
Mr Bethune described the trip as a ''big learning experience''.
With victory in the S4 Masters Stock Moto final, Matthew Hamilton (30) of Christchurch, headed Kiwis on the podium.
Auckland-based international Daniel Bray (S1 Stock Moto) and Christchurch's Marcus Armstrong (S5 Stock Moto) both finished third in their finals.
As well as the top kart racers from the US, Europe and Oceania, the event attracted entries from top single-seater and tin-top racers, such as Australian IndyCar star Will Power, four-time ChampCar champion Sebastien Bourdais, from France, and Nascar drivers Jamie McMurray, AJ Allmendinger and Scott Speed.
