# CDI (capacitor discharge ignition)

> A CDI (capacitor discharge ignition) unit stores energy in a capacitor and dumps it into the ignition coil to create the spark at the spark plug.

- **Also known as:** Ateşleme beyni, CDI ünitesi, Capacitor Discharge Ignition
- **Turkish term:** CDI
- **Category:** [CDI Units & Ignition Coils](https://motorsikletparcasi.com/en/category/cdi-units-and-ignition-coils)
- **Page:** https://motorsikletparcasi.com/en/glossary/cdi

The CDI sets the spark timing (advance) from the signal of the **pickup coil**, which reads a trigger lug on the flywheel. There are two main types:

- **AC CDI:** powered directly by the [stator](https://motorsikletparcasi.com/en/glossary/stator).
- **DC CDI:** powered by the battery; a weak battery means a weak spark.

## Symptoms of a problem

- No spark at all
- Cutting out or misfiring at a particular rpm
- Stalling when hot and restarting when cool

Before replacing the CDI, check the [spark plug](https://motorsikletparcasi.com/en/glossary/spark-plug), [ignition coil](https://motorsikletparcasi.com/en/glossary/ignition-coil), pickup and wiring connections.

## Related terms

- [Ignition coil](https://motorsikletparcasi.com/en/glossary/ignition-coil): The ignition coil is a transformer that steps up the low voltage from the CDI or ECU to the many thousands of volts needed to fire the spark plug.
- [Spark plug](https://motorsikletparcasi.com/en/glossary/spark-plug): A spark plug ignites the fuel-air mixture in the cylinder with a spark across its electrodes.
- [Stator](https://motorsikletparcasi.com/en/glossary/stator): The stator is the set of fixed coil windings inside the flywheel that generate alternating current together with the flywheel magnets.
- [Flywheel magneto](https://motorsikletparcasi.com/en/glossary/flywheel-magneto): The flywheel is the heavy rotating disc on the crankshaft that carries magnets; with the stator it generates electricity and smooths engine rotation.

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- Source page: https://motorsikletparcasi.com/en/glossary/cdi
- Last updated: 2026-10-09
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