Here is a chainsaw powered bicycle I built on the cheap. Chainsaw I inherited, $10 for throttle control, $25 for both moped wheels, $20 for #41 chain, $8 for steel for kickstand,$15 seat,$22 miscellaneous hardware for chain tensioner and drive sprocket. Bike frame cost $20 but I bought three similar bikes at the same garage sale and sold one of the bikes(skiptooth) and broke even so bike was free.