If you're looking for off road adventure why not take a look at the Nevis Road? This is a summer only road (closed during winter months) and offers over 100km of fun along with multiple water crossings. You'd be foolish to attempt this on anything other than a dirt focused motorcycle, hiring something like our DR650 or DRZ400 would be ideal.
The Nevis sits between Cromwell and Garston, a steep climb in or out from either end leads to a hidden valley, once the home to 3,000 gold miners but now largely uninhabited, this is a harsh environment in winter but beautifully remote in the summer. While you could dash through in 1.5hrs if you want to take in the history allow 4 - 5 hrs. And of course take your lunch.
I've usually ridden this north to south after spending the night in Cromwell. It's a steepish climb out of Bannockburn with spectacular views to the north over Lake Dunstan. Then the drop down into the Nevis Valley where the track continues on south with multiple water crossings. The going is mainly pretty good with semi maintained 4x4 tracks being the norm, some of the water crossings can get pretty deep so pick you route through. At the south end the route rises up again with fantastic views to the south and west, take a camera and a warm jacket, it can be cool even in mid summer. A real back country adventure.
Once you're through take SH6 back to your starting point, dipping in to Skippers Canyon along the way if you have time. 24hr fuel in Kingston.