Mostly self guided
Very easy country to do self planned, its long and skinny and not as many roads to choose from like Europe or even UK.
I'm sure your NZ friend will steer you right. I'm a north islander and a little biased but the yes the south island is motorcycle heaven and there is nobody there!
Stay away from Auckland if possible but a ride to the top tip of the north is worth it (Cape Reinga). When you come back down, a ride around the Coromandel Peninsula is well worth the effort. Its coastal and winding. A night there could be pretty cool too as its quite old fashioned and the little towns are like what we grew up with.
As a geothermal country there are numerous places to have a hot dip (don't put your head under), stiles at a farm fence leading to a hole dug into the field are not uncommon, especially if you acquire local knowledge. But a big fav while you're in Taupo (you'll go through Taupo, its hard to avoid and worth the ride through around the impressive crater lake) is De Bretts. You walk down into a valley and is best at night for the whole atmosphere (steam and ferns). https://www.taupodebretts.co.nz/hot-pools/outdoor-pools
I'm from the Hawkes Bay but spent a little time in the Waikato and a hot pool experience you will not usually see on the tourist literature is Te Aroha Mineral Pools. At the bottom of mount Te Aroha (translates: Mountain of love) and fed from a spring the soda water filled wooden tubs are out of this world. If you have your better half with you I can recommend this for a divert. https://www.mpdc.govt.nz/our-facilities ... neral-spas
. Te Aroha is a cool little farming town with 2 pubs and quirky B&Bs too.
Next day you could roar over the ranges along the Mamaku (steep, winding and fast with passing lanes, watch for coppers) into Mount Maunganui. Or you could ride the northern route from Te Aroha going through Paeroa and the Karangahake gorge (very scenic and winding but you can get caught behind slower vehicles). When I was a local it was very popular to do the whole circuit, about 4 hours. Mount Maunganui is worth a visit, lovely beach and loads of restaurants for all budgets, it can get packed with tourists but you'll have no problems parking bikes near you. Walk up the mountain for a leg stretch, about 45 minutes, medium+ fitness. View is exceptional. This is the Bay of Plenty as named by Captain Cook. https://www.bayofplentynz.com/things-to ... k-15043221
Hawkes Bay has lots of wineries if you're into all that. A favourite thing to do when living there was a ride up Te Mata peak for and outstanding view of the Plains on a fine day.https://www.newzealand.com/uk/feature/te-mata-peak/
I can recommend this if you're passing the Bay, which you should, the west of the island is just forest, bush, volcanoes and desert road. I am biased.
Mount Taranki and the other volcanes (Ruapehu and Ngauruhoe) in the West are impressive from the road....But its all a bit out of the road on your route South to heaven. If you do take that route, look at staying in Ohakune and taking the sky Waka up the volcanoe. This is a new thing, I've not done it but heard its excellent. Ohakune is the Queenstown of the north with many less humans (Queenstown 20,000...Ohakune 1,000 pop.)
Take lots of money as everything is more expensive than the UK these days. Use Airbnb.
NZ is a very Harley country, highest ownership per capita in the world apparently. The majority of HD riders won't wave, don't take offence, its just the way we were brought up
. At the stops everyone will be super friendly though.
You'll have great trip, looking forward to hearing how it all goes. If I can think of any more local tips that the tourist map wont have I'll drop you a message.