NEw here want to build a bike.

Hey guys joined the forum cuz. I'm kinda into bikes. All i have is a manual bike. Its green and a little rusty tires are flat. Those are minor problems and can easily bee fixed. But what i want to do is turn it into motorized bike.. I recently watched an episode of american chopper where they used a lawnmower engine which was instinctively my first guess for an engine but i can find a  weed wacker engine as-well.\

Does any1 know what parts and pieces i'll need to make this bike work.?YOu know how to connect the engine where the bolts will go. I really dont know a thing about bikes except probaBLY how to put gas in. but if it takes me a while to do it i'll work on it until it's done . Can u all help ?.