A motorcycle. An ongoing engineering project.

My GPX 250
Twin Brighton.

I’m Sergei. I developed TrueKeylessGPX and EasyRide for my own GPX 250 Twin. This site documents those projects and the other electronics and mechanical improvements I’ve made to the bike.

Explore the modifications

Earlier GPX 250 Twin Brighton setup, with a rear top bag but without the windscreen, auxiliary lights, forward footpegs or side bags — **Before**The earlier setup

My GPX with five numbered annotations: windscreen, auxiliary lights, forward footpegs, side bags, and an electronics block for keyless ignition, self-cancelling turn signals, trip computer and onboard diagnostics — **Now**The current setup

The modifications

From the wiring
to the way it rides.

Each project starts with something I want to understand or improve on my own bike. Here are the decisions, the details and the work along the way.

The GPX 250 Twin is a good city bike. I’ve been riding mine every day for almost two years now. It has its strengths, and it has its weaknesses.

What I like

It’s fucking beautiful. No, let me put that differently. It’s fucking gorgeous, and the whole design just works.
The brakes are excellent.
It holds the road brilliantly in the rain.
It carries my 105 kg bulk and a beautiful, graceful pillion passenger in reasonable comfort.

What I don’t like

Gear changes. An oil change helps, but only for a while. I use fully synthetic 10W-50.
The vague turn-signal switch. Sorted that out with my self-cancelling turn signals.
Vibration at high revs. Above 90 km/h, it gets so bad that you might as well stop looking in the mirrors: you can’t see a thing, everything is shaking. No fix for that.
The instrument cluster. An awful creation by some nameless developer. See my complaints about the stock cluster for the details. The cure is a complete replacement: my DIY instrument panel.

Dear gentlemen at GPX: I understand that you got a ready-made engine. It is what it is. But how could you accept that instrument cluster from your supplier? Where were the validation and verification? I can set up an R&D department and a testing team for you.

TrueKeylessGPX

Keyless ignition.
Built around my GPX.

The control unit and its dedicated pin-to-pin harness for the GPX 250 Twin. Keyless ignition, turn signals, trip recording and diagnostics began here, on my own motorcycle.

Explore TrueKeylessGPX

Electronics & signals

01 / 06

Keyless ignition

TrueKeylessGPX

I developed this system for my GPX 250 Twin, complete with a dedicated pin-to-pin wiring harness.

TrueKeylessGPXRead more 02

Keyless ignition

EasyRide

A fully open-source keyless ignition device I developed for my GPX, using a phone for access and starting.

EasyRideRead more 03

Self-cancelling turn signals

Controls & firmware

Using speed, distance and braking context to decide when to cancel.

TrueKeylessGPXRead more 04

Trip computer

Signals & riding data

Turning the motorcycle’s signals into useful information about a ride.

TrueKeylessGPXRead more 05

Engine diagnostics

ECU integration

The engine-diagnostics branch of the TrueKeylessGPX project.

TrueKeylessGPXRead more 06

Inside the stock GPX instrument cluster

A three-part investigation

Reverse engineering the stock GPX 250 Twin cluster: disassembly, connector pinout, bench tests and input signals.

GPX workshopRead more

Stock GPX instrument cluster disassembled on the bench

From the notebook

First, find out
what’s already there.

A 20-pin connector. Speed and RPM signals. A board with an unmarked microcontroller. The stock GPX instrument cluster was a good place to start.

Inside the stock GPX cluster

I like to understand
how things work.

I’m Sergei Kuzmin, an electronics engineer. My professional work has included embedded systems and electronics for autonomous vehicles. Motorcycles are a personal interest—and my GPX gives me plenty of reasons to get back to the workbench.

I document these projects to share what I find: the signals, the circuits, the design decisions and the details that are easy to miss.

Have a technical question? Get in touch

Elsewhere in my workshop

Motorcycle electronics

SmartMoto.Asia ↗

TrueKeylessGPX, EasyRide and the practical information behind the products.

Another personal project

DOGS² ↗

A compact power and diagnostic station for bringing new boards to life.

My GPX 250
Twin Brighton.