What Is a CDI on a Loncin ATV 110?

Knowledge of your Loncin ATV 110's electrical system proves handy the first time you try to start it and nothing happens. To start an engine, all you need is fuel, spark and compression. The 110's capacitor discharge device, or CDI, provides the spark in this equation.

  1. Electrical System Basics

    • The stator plate, which Loncin mounts around the crankshaft of the 110 combustion engine, generates the current that ignites the fuel. The motion of the crankshaft rotates a circular magnet around the stator plate, which produces a current. This current powers auxiliary circuits such as the headlight, tail light and the CDI box.

    The CDI Box

    • The mechanical motion of the engine generates voltage, which the CDI boosts to achieve a strong and consistent ignition spark in the cylinder every time the engine completes its compression stroke. The CDI contains two key components, the capacitor and the inductor. The capacitor stores the charge the stator plate produces. Once the capacitor reaches its capacitance, it releases its charge to the next stage of the circuit, the inductor. The inductor is a square magnet with a small copper coil wrapped on one side and a larger copper coil wrapped around the opposite side. As the capacitor dumps its charge onto the primary coil of the inductor, the voltage induces a higher voltage in the secondary coil. This higher voltage travels to the spark plug to burn the compressed fuel.

    Locate the CDI

    • The spark plug sits in the center of the cylinder head.

      Look under the seat of a factory-condition Loncin 110 ATV. If the CDI is not in its factory location, find the spark plug in the middle of the cylinder head on the engine. Feel for the rubber cap that covers the spark plug and follow the thick wire coming off the cap. This wire leads to one side of a small black cylinder called the coil. Protruding from the other side of the coil are two wires, green and yellow/black. Follow the yellow/black wire to to a larger black square box, the CDI.

    How to Test the CDI

    • The tip of the spark plug contains electrodes.

      To tell if the CDI box is functioning, remove the spark plug with the cap and wire attached and touch the threads of the spark plug to a metal part of the frame or engine. Turn over the engine a few times with the electric start or kick-start, and look for a bright blue spark between the electrodes of the spark plug. If you see a spark, the CDI is working.