Hey, I have a 36V 250W hub motor e-bike with a KD58C display and an AMYD3613 controller (13A).

The bike is limited to 25 km/h (EU regulation). In the display settings I can set higher speeds (like 40 km/h), but it doesn’t actually change anything — it still cuts power at 25.

I installed a thumb throttle (3-wire: red/black/green) and it works properly. The bike gives power with throttle, but still cuts at \~25 km/h, same as with pedal assist.

The interesting part is that the system feels “smart” — it increases power when going uphill or when there’s more load, even though it’s just a cadence sensor (not torque sensor).

There is no external wheel speed sensor (no magnet on spokes), so I think speed is calculated from the motor hall sensors.

I also found:

• a 3-pin connector for throttle (confirmed working)
• an unused 4-wire connector (black/red/white/yellow), possibly for display or diagnostics
• no obvious limiter loop wires

The behavior is that once the bike reaches \~25 km/h, it cuts power immediately. This happens consistently and was like this from the factory — not related to braking or any setting changes.

I also tried changing wheel size in settings (26" → 28"), which increased speed slightly (\~2–3 km/h), but didn’t remove the limiter behavior.

So my questions:

• Is the speed limiter hardcoded in this controller?
• Is there any way to unlock it (wiring, settings, firmware)?
• Can the KD58C display be replaced with something that allows higher speed?
• Or is replacing the controller the only real option?

Any help appreciated 🙏