How Do You Bypass a CDI Box?

You can bypass a capacitor-discharge ignition (CDI) box temporarily for troubleshooting purposes. Since a CDI box transmits voltage from the pick-up coil in the stator to the ignition coil and does not generate continuous sparks, it cannot store enough voltage to keep the engine running.

  1. Clear your workspace

    Since a CDI box ignites the air and fuel mixture that powers your engine, clear your work area of all flammable liquids, such as gasoline. Keep a fire extinguisher nearby.

  2. Check the battery

    Test the battery to verify it is fully charged. Replace it if necessary.

  3. Identify the CDI box

    Locate a black box with two plugs and a bullet connector. A pin connects to the pick-up coil in the stator, and another pin connects to the ignition coil, which sends the spark to the spark plug.

  4. Ground the current wire

    Ground the wire coming from the stator to the motor.

  5. Disconnect wires

    Disconnect the main wires coming from the CDI box.

  6. Bypass the CDI box

    Attach a jumper wire from the positive battery terminal to the positive wire on the ignition coil. Attach a jumper wire from the negative battery terminal to a ground.

  7. Observe the engine

    If the engine sparks, you have confirmed a failed CPI box. If the engine does not spark, your problem is not a faulty CPI box.