Select your scooter. For this task, a sturdy frame constructed of metal (such as aluminum) or wood is a requirement. Remember that this scooter will likely be traveling at speeds faster than originally intended, so a solid design from the ground up is best. If you are purchasing a scooter secondhand, keep a sharp eye out for wear-and-tear, such as cracks in the frame or parts that are malfunctioning. Select a scooter that has large tires and solid hand-operated brakes.
Purchase the motor that will be used for this project. Specialty retailers carry kits that supply brand-new gasoline engines and mounting equipment, or you can purchase a motor second hand. Salvaging an engine off of another piece of equipment, such as a chainsaw, can be more affordable than buying a kit, but it is more challenging to install. Motors that have 49cc's of displacement or less are usually street legal in most areas, but double-check your local laws to make sure before purchasing an engine.
Prepare the rear wheel to receive power from the motor. In its stock state, the rear wheel will have no mounting system, so you will need to improvise a sprocket for the chain to connect to. A bicycle sprocket is ideal for this application, since the chain size is perfect to transmit power from the engine to the wheel. Examine the axle to determine the best mounting system for your specific scooter. In some cases, a larger axle that extends beyond the side of the scooter can be used to attach the sprocket. On other designs, you may have to purchase a thinner wheel and tire combination and attach the sprocket into place in the gap left by the thinner wheel.
Mount the motor on the deck of the scooter. After test-fitting for placement, drill holes through the deck of the scooter that are slightly larger than the bolts that will be used. Once the holes are drilled, insert the bolts. Place washers of the largest reasonable size between the nut and the scooter, and also between the head of the bolt and the engine. Vibration-dampening washers placed between the motor and the scooter will help provide a more peaceful ride. Connect a bicycle chain from the output shaft to the sprocket on the wheel (the chain may need to be shortened). Finally, run the throttle-control cable up along the scooter and mount it on the handlebar in an easy-to-access location.
Take the scooter for a test drive, paying careful attention to any unusual noises or vibrations. Make sure the chain and any other moving parts are clear of your legs, and that no loose clothing could possibly get snagged up in it. Test the brakes to make sure they can rapidly stop the scooter. If there are any unusual problems, stop driving immediately and fix the problem before riding again.
Tips and Warnings
A scooter, whether built for fun or for commuting, will be mostly the same, so let's take a look at the tried-and-true method of building gas scooters that has been popular across the globe for decades.
Building the actual scooter itself from scratch can be a very time-consuming task, and if done improperly, can be dangerous to the end user. Since secondhand scooters can usually be picked up for $5 to $10, these steps will focus on adding a motor to an already built scooter.