# Spark plug

> A spark plug ignites the fuel-air mixture in the cylinder with a spark across its electrodes.

- **Also known as:** Ateşleme bujisi, İridyum buji, Spark plug, Bujı
- **Turkish term:** Buji
- **Category:** [Spark Plugs](https://motorsikletparcasi.com/en/category/spark-plugs)
- **Page:** https://motorsikletparcasi.com/en/glossary/spark-plug

A spark plug code (NGK, Denso, Champion and others) describes the thread diameter, heat range, reach and electrode type. Because the wrong heat range or reach can damage the engine, use the code in the manual or the manufacturer's cross-reference chart.

## What the plug colour tells you

- **Light brown / grey:** mixture and temperature are normal
- **Black, dry soot:** rich mixture, choke left on, clogged air filter
- **Wet, oily:** oil burning past the rings or valve stem seals
- **White, blistered:** lean mixture or overheating

Standard nickel plugs are usually replaced every 6,000–12,000 km; iridium and platinum plugs last longer. Check the electrode gap against the manual.

## 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.
- [CDI (capacitor discharge ignition)](https://motorsikletparcasi.com/en/glossary/cdi): 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.
- [Air filter](https://motorsikletparcasi.com/en/glossary/air-filter): An air filter stops dust and particles in the intake air, protecting the cylinder, piston and rings from wear.
- [Choke](https://motorsikletparcasi.com/en/glossary/choke): The choke enriches the fuel-air mixture (adds more fuel) to help start a cold engine.

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- Last updated: 2026-10-09
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