I picked up a nice ICE stinker this week. A 2 stroke 50cc Honda MB5. Its a 7hp, or 5250 watt bike capable of 60mph. Lots of fun!For a motorbike, its extreamly light weight. 149lbs empty. But looking it over more carefully, Its clear that anyone building a bicycle to do 60mph needs to re-think things. That being me. I'm also welding up a frame for a 60mph Ebike. The MB5 is built to handle speed. the frame is heavy guage steel, triangulated for stiffness. larger bearings and axles to handle higher forces at speed. Larger, thicker brakes to scrub off the extra kenetic energy. stronger rims to handle bumps and hitting potholes at speed. Headlights, brake lights, and turn signals so people actualy see you.
As a motorbike, this is the bare minimum of what a motorbike needs to handle speed. They can't even legaly make motorbikes like this now, its too light weight and doesn't meet current DOT rules. Too fast for a moped, too slow for the highway, too lightweight to be safe. But compared to what I'm building for an Ebike, this thing is a heavy weight monster.
Granted, My ebike won't be built to go 60mph often. But after seeing this bike close up, its clear that any bike built to handle high speeds needs to be stronger than a bicycle.
(Not my bike, but same model)
Lots of us really need to weld, or pay somebody to weld. 
