How to Hook Up a Motor to a Chopper Bicycle

Bolt the motor to the bicycle frame so it's cradled between the down tube and the main tube of the frame. Motors designed to drive a sprocket, instead of driving the bike by directly contacting the wheel, will mount to your bicycle's frame tubes. Once set in place, have a helper balance the motor while you fasten a clip that secures the motor mount to the tube using machine screws. Depending on the kit, you'll tighten the machine screw with a screwdriver or a wrench.

Install the sprocket adapter. The sprocket adapter is added to the existing hub. Remove the rear wheel and bolt the adapter to the hub. When you set the wheel back into the frame, the new sprocket must align in the same plane as the motor's drive sprocket. Adjust the rear sprocket so it aligns to the front sprocket.

Install the ignition system, which includes a coil and a kill switch. The coil will mount to your down tube with hardware similar to the motor mounts. Tighten it in place so the spark plug wire can reach the head of the motor. Tighten the kill switch to the handlebars so you can access it easily with your thumb. Use nylon ties to secure the kill switch wiring and ensure it doesn't get tangled in any bike parts during operation.

Install the clutch lever. Fasten it to the left handlebar just like a motorcycle. The mounting hardware is also like the hardware to mount other components to tubes. It will have a clip that tightens to the base of the lever with two machine screws. Some kits may have a different kind of clip requiring you to slide the handlebar grip off and slide the grip over the handlebar tube before tightening it.

Install the clutch cable. The ends of the cable fit into hand-adjustable cable holds at the lever and the motor where the clutch is located. Some cable holds require a wrench or screw driver to fasten.

Fasten one end of the throttle cable to the throttle assembly, and the other end to the top of the carburetor. These are mechanical connections but typically don't require tools, so long as the throttle assembly is un-assembled when you start.

Install the throttle on the right handle bar and the carburetor. You'll have to remove the existing hand grip and slide the throttle assembly over the bar. Fasten the carburetor to the motor's intake port and tighten it with a wrench. Secure the throttle cable with nylon ties, making sure you don't kink the cable or tighten the ties with enough force to bind the cables.

Install the fuel tank with mounting hardware and run the rubber or vinyl fuel line from the fuel tank's petcock to the carburetors fuel spigot.

Install the exhaust systems by bolting the exhaust pipe flanges to the motors exhaust port. Some kits may also come with support brackets to mount the pipe to a portion of the bike's frame.

Install the chain. On a long, modified chain you my need to use a chain-breaker tool to make a custom-length chain out of two standard chains. Install a chain tensioner or guide, if the kit includes one.