Whimpy64, A big bore kit would give you more power at the rear wheel for sure. I don't know the speed limits for freeways in Australia. Here in the U.S. they are 65 to 70 mph. A bit much for a 170cc bike, especially with your extra weight added. In fact, here a two wheel cycle must be of 250cc or higher to get unto the freeway,interstates. I wonder how hard it would be to move your trike kit to a larger scooter? I think the big bore kit might be less expensive, but the satisfaction level would be much higher going with a larger bike.
I was in Texas some years ago and saw two 750 Honda motorcycles rigged for the rider to remain in his wheelchair while driving the bike. They had sidecar attachments, with the traditional passenger tubs replaced with a platform and small railing around it and the ramp formed the rear railing and it doubled as a ramp. Once the rider was on the carriage, he pushed a lever forward and it came up against the chair wheels and locked him in. The handle bars were moved to the front of the driver and transmitted movement to the triple tree on the bike via bell cranks and rods. I want to say that the bikes had automatic transmissions, as Honda tried them on 750 and 400cc m/c. They had mounted a grab bar over the fuel so that a passenger could mount where the driver would have normally sit and had two windshields. Wish I had a picture to send you and I took some, but there no telling where they are now. Just thought you might enjoy hearing about them and it just goes to prove that where there is the will, so there is a way. Keep on riding as long as you can mate.
Mac, aka "ole two wheels"
