About a year ago, my dad and I had the idea to convert a beach cruiser bike into an electric motorcycle. We purchased the bike and all the parts necessary and got to work. We modified the frame and rebuilt the bike from the ground up. When we finished, we were extremely satisfied with the results - a 48 volt, 15 horsepower board track racer.
Step 1: The Components
We started with a Felt beach cruiser because it had the right look. We wanted a beefy bike that could fit all the components. The goal was to keep the center of gravity as low as possible. Here are the rest of the main components we purchased:
- Briggs and Stratton Etek motor (now discontinued)
- Alltrax AXE 300-amp programmable controller
- Magura 0-5K ohm twist-grip throttle
- 4 x 12V, 21Ah sealed lead acid batteries
- Avid BB7 mechanical disc brakes (160mm rotors)
- #35 moped chain
- 13-tooth drive sprocket
- 66-tooth rear sprocket
- big power switch
- 300-amp fuse
- 8 1/4 in. stainless steel motor mount (this replaces the original bottom bracket)
Step 2: Front Fork
We removed the original rigid front fork and replaced it with a Manitou suspension fork. We also bolted on an Avid disc brake set to the front end. We chose to go with mechanical discs instead of hydraulics simply because they are less expensive and less complicated. The Avid BB7's are fully adjustable. You can dial in each pad separately.
Step 3: Rear Brake Mount
Because the bike we purchased used coaster brakes (pedal backwards to stop), we had to fabricate a mount in the rear to accept our other disc brake. We used a jigsaw to cut out a piece of steel for the main shape. Next, we used a drill press to tap holes for the brake.
Step 4: Rear Hub/Sprocket
The rear hub we used is designed as a "dual disc" front hub. It has a standard mountain bike 6 bolt disc pattern on both sides. We took a blank 66 tooth rear sprocket and drilled it to accept the 6 bolt pattern. The alignment of the hub, sprocket, and disc rotor are critical.