Re: What motor kit should I get for this bike?
get a motorcycle helmet for that thing. you will face plant many times lol. i had one of those, i would lengthen the wheelbase if i put an engine on it. you could use a rc car nitro engine and transmission to drive the pedal chain! a weed eater is difficult to make a reduction drive for, and it will need it if you plan to go less than 20mph. try to find a motor scooter, it's like a kick scooter with an engine. you could swap out the back wheel from it, brakes, throttle, and the engine with the gearbox. they are pretty compact as well.
some people say that a motorbike defeats the purpose of a bike. i tell them to get a flintstone's car.