Doing an electric conversion on any bike requires the use of an electric motor. There are lots of options when it comes to what motor to use. Do you want hub or mid-drive, front or rear hub, geared or gearless? I knew that I was going to need a pretty powerful motor to get a fairly heavy moped up to 30-40mph. The plan was to get a gearless rear hub motor because; 1. I needed to get a rear wheel regardless (it was missing), 2. Rear hubs give you lots of direct torque for climbing hills and good acceleration, 3. The weight distribution towards the rear of the bike feels more natural to me, and 4. Gearless motors are generally more reliable, quieter and cheaper due to less moving parts.
After weeks of research, I decided on a 1500w gearless direct drive rear hub motor that I found on eBay.
I wanted to keep the look of the original moped, so I ordered 17” chrome rims for the wheels and 10g stainless spokes to lace with.
I was able to calculate the spoke length using a handy-dandy spoke length calculator that I found online: https://www.prowheelbuilder.com/spokelengthcalculator. Turns out that I needed 166mm spokes for the front and 140mm spokes for the rear.
After the motor, rims and spokes arrived it was time to lace the wheels. To keep the moped’s original look, I used a two-cross pattern for the spokes. Through some trial and error, I was able to complete the wheels. I will say that the front was definitely much easier to lace than the rear, due to the fact that the motor was quite a bit heavier than the front hub and a little awkward to work with.
After lacing the wheels, I mounted the tires on the rims. This process was fairly easy using the zip tie method. I went with ~40psi in the front and ~50psi in the rear for a smooth fast ride!
My next challenge was the fitment of the rear wheel. The swing arm of my moped had originally had a dropout spacing of 125mm, which was going to be too narrow for the 135mm dropout of the new rear wheel. I used a custom tool that I made in order to spread the swing arm to ~140mm to accommodate the rear wheel. I used some nuts, washers and all-thread from the local hardware store to make the spreader.
Once I got both of the wheels on the moped, I wanted to get the wheels as true as I could. I used a zip tie on either side of the front fork and on either side of the rear shocks, as my fixed points to allow me to true the wheels.
Next up was brakes. For the front brakes I used the original drum brakes that came with the moped. I ordered new brake shoes and installed them.
Now on to the rear brakes. I was forced to use a disc brake in the rear which was going to require a little bit of re-design. I order a rear mechanical caliper and disc from Amazon, that came with the brake cables as well. I also ordered a mounting adapter that I could modify to mount to the moped.
So after measuring and re-measuring and fitting and re-fitting, I was able to have a functioning rear disc brake!
I learned quite a bit about wheels during this process. In the end, the results turned out great! So with the wheels on, the mechanical portion of the moped build was complete. Next up was to install the 12v lighting/horn.
The Electric Moped Project 