Ebike Build: Borderline Motorcycle

July 3, 2026

I have a Facebook Marketplace addiction.
When I found a full suspension eBike for $100 I had to take it.

The catch? It didn't run.
Easy, I used to build EV's at Tesla, a bike will take minutes.

A Facebook Marketplace chat about the e-bike listing.The red e-bike from the Marketplace listing.

And...I bought it.
I thought there was just a cut wire somewhere and it would take 10min to fix.
Step 1 was getting everything on table and do continuity tests.

The e-bike electronics and test gear spread across a workbench.The bike frame and parts laid out on a table for testing.

We got some signs of life after putting a screwdriver in the ignition and getting the battery terminal properly mated.

The e-bike dash powered on and showing signs of life.

I also saved this guy's life when I bought it, wheel was minutes a way from coming off. "Knock knock knocking on heaven's door."

The loose front wheel hardware that nearly came off.

After getting everything to turn on, I found a glowing "M" on the dash, likely Motor.

Inside the motor we have two candidate issues:

  1. The Halls aren't getting power or are fried.
  2. The motor windings melted the enamel and there's a short.

The motor has red, black, yellow, green, blue, and white.

My guess is red and black is power. Yellow, green, and blue smell like motor wires. White I have no clue.

Tapping white, I notice that free spinning the wheel changes the pulse width. Speed sensor!!

Now the halls, I put 5V through the red and black wire and spin the wheel. One of these pictures is not like the other and we find our culprit.

A Hall sensor scope trace with a clean signal.A Hall sensor scope trace showing the bad signal.A second Hall sensor scope check during diagnosis.

So now we replace that hall! Thankfully I love motors, and I had spare chips in my closet.

The exposed motor Hall board during repair.

Success!
Sort of, with the motor fixed, the error did clear, but still no start.

Battery has voltage and motor seems fine, so why isn't the controller sending a signal?

Unfortunately, the motor controller does not show any sign of life, and I have...another one.

A bigger one.

Left is old (1 KW / 1.34 HP), right is new (10 KW, 13 HP)

The original controller next to the larger replacement controller.

This is the part of the project where the FB marketplace shit box turns from a nice saturday to a quest.

A workshop banner that says we do this not because it is easy, but because we thought it would be easy.

I also lost the key, so I learned how to lock pick with a drill (I had to replace the lock)

Drilling out the old lock after losing the key.

But because I'm using a new controller, I need new hard to steal brackets to mount the controller on. I chose my favorite (bad?) habit which is retaining nuts in everything. I ran out of filament, so gotta spray paint those later.

The new controller mounted with custom brackets.

But now with the battery and controller in new places, i had to redo the entire wiring. Including figuring out how the brakes work (thankfully just a switch) and the throttle (thankfully just 0-5V).

Except for the throttle bottom being 0.8V. That would've been a nice accident. If I just assumed 0, this thing would fly the minute you turned it on.

But thankfully we can tune that in the Kelly Controller (love this thing).

Wiring is sort of like sanding:

  • I hate it
  • I have to do it
  • It always takes more time than I plan.

In my heart of hearts I really thought this would be 20min of work for me. I spent 8hrs.

The rewired bike with battery and controller installed.

With that, we have a sweet ebike. (Not a motorcycle, motorcycles don't have pedals, and you have to register them and buy insurance.)

The finished red e-bike in the garage.