These motors can be removed from electric strollers used with children under the age of five. Every stroller uses one motor for each drive wheel, usually two for the rear wheels. Each engine is powered by a 15 volt Vcc+ battery or a lead electrode sulfuric acid motorcycle battery can also be used. In the video of the four motors to turn the rear wheel of the bike I suggest you add a dynamo or two to be used to generate electricity and charge the battery, a system similar to that of a real car, Of course, the voltage of the dynamo fan should be checked, but this is one for many more duty cycles. Having an electric battery would also be practical. I also recommend installing front and rear fenders and an enclosure to isolate the electric motors from getting wet from the rain or through puddles.
We will see how to make an electric bike from 775 engine. I used four 12-24v dc motors (775 motors) here, and you can buy 24v, 14A batteries online from amazon. You can find the 775 engine here: