OP, search you tube, there are plenty of videos about motorized bike kits. It looks like there are 4-stroke kits that are better. The 2-stroke ones were widely used by commuters in China until their government outlawed them due to their contribution to air pollution. Chinese commuters are now using 4-strokes and/or electrics instead. I had a couple of Whizzers back in the late 1950's. They were real cheap on the used market, but not very dependable. Google and check your actual local laws before taking your creation onto the streets; don't rely on advice from random people.
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My C&V Bikes:
1972 Bottecchia Professional, 1972 Legnano Olympiade Record,
1982 Colnago Super, 1987 Bottecchia Team C-Record,
1988 Pinarello Montello, 1990 Masi Nuova Strada Super Record,
1995 Bianchi Campione d'Italia, 1995 DeBernardi Thron