The north shore part of Oahu is going to be a two lane highway called Kamehameha Highway, it s two lane and it would be difficult to work you way completely around the island in a day where it would take 2 hours by car to complete the circle of the island. You ll be hurting the next day if you did that and it would be dangerous to ride a moped along the north shore on a moped where you d have to share the roads with cars.
I m not 100% on this, but I ve been to Oahu many times, and I asked one of the locals this question once. He said he wouldn t recommend it. The only way to get to the North Shore is the highways. Also you would most likely get soaked with rain as it is usually raining somewhere along the way LOL.Renting a tracker is pretty much just as cheap as the scooters anyway :)