In NZ we have “restricted” and “unrestricted” licences. Restricted means as a New Zealander you can ride no more than a 250cc motorcycle (no power limits yet..) if you are over 25, and successfully complete all the skill based tests, you can obtain an unrestricted licence in 9 months. If you are under 25, it takes from 12-18 months.
But here’s the interesting thing: If your licence in your country states that you can ride a 650cc motorcycle in your country, then you can ride a 650cc here, using your licence. The NZ laws state that you are able to ride the same capacity motorcycle in NZ, that you are licenced for in your own country ( they don’t mention power ratings).
If you have a current full licence in another country, it is valid here. You don’t need to bring an International Driver’s Licence.