# Crankshaft

> The crankshaft converts the piston's up-and-down motion into rotation through the connecting rod.

- **Also known as:** Krank, Krank seti, Crank
- **Turkish term:** Krank mili
- **Category:** [Crankshafts](https://motorsikletparcasi.com/en/category/crankshafts)
- **Page:** https://motorsikletparcasi.com/en/glossary/crankshaft

On small single-cylinder engines the crank is usually a pressed-up assembly: two flywheels, the crankpin and the [connecting rod](https://motorsikletparcasi.com/en/glossary/connecting-rod) are sold as one unit. It turns on main [bearings](https://motorsikletparcasi.com/en/glossary/bearing) and is sealed with oil seals at both ends.

## Symptoms of a problem

- A knock from the bottom of the engine that gets worse under load (big-end play)
- Increased vibration (crank run-out)
- Rumbling (worn main bearings)

When replacing a crankshaft, renewing the main bearings and seals is recommended.

## Related terms

- [Connecting rod](https://motorsikletparcasi.com/en/glossary/connecting-rod): The connecting rod links the piston to the crankshaft and transfers the piston's linear motion into crank rotation.
- [Piston](https://motorsikletparcasi.com/en/glossary/piston): The piston moves up and down in the cylinder and transfers combustion pressure to the crankshaft through the connecting rod.
- [Bearing](https://motorsikletparcasi.com/en/glossary/bearing): A bearing is a machine element that reduces friction between a rotating shaft and a fixed housing using balls or rollers.

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- Source page: https://motorsikletparcasi.com/en/glossary/crankshaft
- Last updated: 2026-10-09
- Türkçe sürüm: https://motorsikletparcasi.com/sozluk/krank.md
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