Before you start: disconnect the battery (negative terminal first) before unplugging or splicing anything. Wire colors on these machines are not standardized – the same color can do a different job on another brand. Always confirm a wire with a multimeter before you connect it. Never connect the CDI’s black/red wire to battery power: it carries AC from the stator, and 12 V DC can destroy an AC CDI.
The five wires that make it run
A kick-start horizontal engine (such as the Lifan-type 1P52FMH 110cc or the YX-type 154FMI 125cc) doesn’t need a battery to run. The stator generates its own AC for the CDI, so the minimum harness is:
| Wire | From → to | Job |
|---|---|---|
| Black/red | Stator → CDI | Source coil: powers the CDI |
| Blue/white | Stator → CDI | Pickup: tells the CDI when to fire |
| Black/yellow | CDI → coil | Fires the ignition coil |
| Green | Stator, CDI, coil → frame | Ground |
| Black/white | CDI → kill switch | Stops the engine when grounded |
The yellow and white stator wires power lights and charging. On a race or pit bike without lights, tape them off separately so they can’t touch each other or the frame.
Wiring without a kill switch
You can run without a kill switch for testing – untick it above and the diagram shows the black/white wire taped off. Don’t ride like that: without a kill switch the only way to stop the engine is to stall it or choke it. Fit a handlebar kill switch before riding.
Testing for spark
- Wire only the ignition section (steps 1–7 in the checklist).
- Remove the spark plug, put it in its cap and hold the plug body against bare engine metal with insulated pliers.
- Kick the engine over and look for a blue spark. Weak orange spark or none: work back through the checks for each wire.