First, you 86 the pedals. Get smaller diameter, fatter tires. Add a big comfortable seat with a small engine under it. No crossbar. Enclose the working parts and fuel tank within a metal or plastic body. Add lights, horn, and brakes. Turn signals are nice. And there you have a bicycle that is built as bicycles should be. Why is it taking people so long to accept that? As for the old bikes with pedals, crossbars, etc., I have a shed full of them that you can buy cheap. That is, if you like to sweat.
How"Pedals! Bah!"ard