Lias:
Not at all
Your argument that only cars and motorbikes contribute to road upkeep is just patently false. Registration does not pay for roads. Fuel taxes only pay for the roads that cyclists cannot use, because they're highways. You know what pays for the roads cyclists use? Rates. Because local councils and property developers build and local councils maintain them, not Waka Kotahi.
Lias:
If ACC risk pricing exists, then yes, I am 100% in favour of making skiing, sport, etc ridiculously expensive to cover the injury bill. Right now motorcyclists are the only group targeted and that's ragingly unfair. Everyone, or noone, equality for all.
As you note, motorbikes get reamed by ACC because of the risk and they have to pay that huge rego per bike they want to ride on the road.. but you don't have to register a vehicle or have a driver's license if you don't use it on the road. Cyclists should also be licensed and have to pay per bike if they want to use them on the road. You wanna mountain bike? Cool, go nuts, but transport the bike there and back with your car and only ride it offroad, or cough up.
Motorbikes get reamed because ACC is a compulsory first party motor vehicle accident insurer. Which means that the cost is directly proportional to the risk the individual takes by using that motor vehicle. The levies are contributed to the Motor Vehicle Account, which only covers motor vehicle accidents that occur on public roads. ACC also says that the motorcycle levy only funds 22% of the full cost of treatment for accidents involving motorcycles, the rest coming from other accounts. You might note the word "motor vehicle" coming up a lot, which is kind of important. Off the top of my head, bicycles are not motor vehicles.
The Earner's Levy on your salary or wages pays into the Earners Account which covers the cost of injuries during sports and recreational activities. Are you arguing that people who do sports should pay levies on their earnings? That's just plain ridiculous.
Side note, by your twisted logic you should be required to get a pedestrian's license and pay pedestrian registration to use footpaths, because pedestrians also use footpaths and roads, and worse yet they sometimes trip or get hit by cars or motorbikes so there needs to be levies on pedestrians to cover that risk!