reply from AA New Zealand
Heres some information i recieved back From the AA
The Registration in the Home Country must remain Valid at ALL Times while you are away. We advise the Transport Registry Centre in NZ that your Motorcycle is o’seas and they Tag the Computer so that when your NZ Person applies to Re-License the Bike, a NZ WOF is not required and renewing can take place, the Windscreen card is then Couriered to you by your NZ Person.
The Issue over you Californian Rego is up to you, If you can keep it Registered there O.K But you would stick with the NZ Plates while travelling on the Carnet supplied by us, you just would not use the Carnet if not required. You must not swap plates until you returned to California and the NZ Carnet is Discharged