125cc CDI Wiring Diagram: A Comprehensive Guide

Getting a 125cc CDI wiring diagram can be challenging, especially if you’re new to wiring diagrams. But don’t worry; this guide will provide everything you need to know about the 125cc CDI wiring diagram. From the basic concept of CDI to the wiring diagram, installation, and troubleshooting, we’ve got you covered.

What is CDI?

The Capacitor Discharge Ignition (CDI) is an ignition system that stores electrical energy in a capacitor and then releases it to the ignition coil in a controlled manner. This system is widely used in small engines like motorcycles, scooters, and ATVs. It provides consistent spark timing and a more reliable ignition system.

A CDI system consists of five main components: the stator, the CDI unit, the ignition coil, the spark plug, and the kill switch. The stator generates electricity, which is then sent to the CDI unit. The CDI unit stores and regulates the electrical energy, which is then sent to the ignition coil. The ignition coil amplifies the electricity and sends it to the spark plug, which creates the spark needed for the combustion process.

125cc CDI Wiring Diagram

Before we get into the wiring diagram, let’s take a moment to understand the wiring color codes. In a CDI system, there are three wires that connect the stator to the CDI unit: the green wire, the blue wire, and the yellow wire.

The green wire is the ground wire, which is connected to the chassis or the engine. The blue wire is the trigger wire, which sends a signal from the stator to the CDI unit. Lastly, the yellow wire is the charging wire, which charges the capacitor in the CDI unit.

Here’s a simple 125cc CDI wiring diagram:

Color Function Connection
Green Ground Chassis or engine
Blue Trigger Stator
Yellow Charging Stator

Here’s how to connect the wires:

  1. Connect the green wire to the chassis or the engine.
  2. Connect the blue wire to the stator’s trigger wire.
  3. Connect the yellow wire to the stator’s charging wire.

It’s essential to make sure that the connections are secure and properly insulated to avoid shorts and other electrical hazards.


Now that you have a basic understanding of the wiring diagram, let’s move on to the installation process.

The installation process may vary depending on the specific model and manufacturer of your 125cc CDI unit. It’s always best to refer to the manufacturer’s installation manual for specific instructions. However, here’s a general installation process:

  1. Disconnect the battery and remove the old ignition system.
  2. Mount the CDI unit in a safe and accessible location.
  3. Connect the wires according to the wiring diagram.
  4. Connect the spark plug and the kill switch.
  5. Reconnect the battery.

After installing the CDI system, it’s essential to test it to ensure it’s working correctly. You can do this by turning on the ignition and checking for spark. If everything works, you’re good to go.


If you’re having trouble with your 125cc CDI system, here’s a simple troubleshooting guide:

No spark:

  1. Check the battery voltage.
  2. Check the wiring connections.
  3. Check the spark plug.

Weak spark:

  1. Check the spark plug gap.
  2. Check the wiring connections.
  3. Check the ignition coil.

Inconsistent spark:

  1. Check the CDI unit.
  2. Check the wiring connections.
  3. Check the stator and trigger coil.

If these troubleshooting tips don’t solve your problem, it’s best to consult a professional or contact the manufacturer for assistance.


What’s the difference between AC and DC CDI?

The difference between AC and DC CDI is the type of electrical current they use. AC CDI systems use alternating current, while DC CDI systems use direct current. AC CDI systems are typically used in two-stroke engines, while DC CDI systems are used in four-stroke engines.

Can I use a 125cc CDI system on a different engine?

It’s essential to use a CDI system that’s specifically designed for your engine model and manufacturer. Using the wrong CDI system can damage your engine or cause it not to work correctly.

What’s the lifespan of a CDI system?

On average, a CDI system can last between 5 to 10 years, depending on usage and maintenance. However, it’s essential to check your CDI system regularly and replace it if you notice any signs of wear or malfunction.

Can I install a CDI system myself?

If you have a basic understanding of wiring diagrams and electrical systems, you can install a CDI system yourself. However, if you’re unsure or have no experience, it’s best to seek professional help.

That’s everything you need to know about the 125cc CDI wiring diagram. Remember to follow the wiring diagram and installation instructions carefully and test the system before using it. If you have any problems, refer to the troubleshooting guide or contact the manufacturer for assistance.