# Valve

> A valve is the mushroom-shaped part in the cylinder head that opens and closes the intake and exhaust ports.

- **Also known as:** Valf, Supap, Emme subabı, Egzoz subabı, Külbütör
- **Turkish term:** Subap
- **Category:** [Valves & Rocker Arms](https://motorsikletparcasi.com/en/category/valves-and-rocker-arms)
- **Page:** https://motorsikletparcasi.com/en/glossary/valve

Each cylinder has at least one intake and one exhaust valve; the intake valve is usually larger. The valves are opened by the [camshaft](https://motorsikletparcasi.com/en/glossary/camshaft) and closed by springs. On SOHC engines **rocker arms** sit between them.

- A worn **valve stem seal** lets oil run down into the combustion chamber; you see blue smoke on start-up.
- Incorrect timing or over-revving can make a valve hit the piston and bend.
- A gas-tight seal between valve and seat is achieved by lapping.

Check the [valve clearance](https://motorsikletparcasi.com/en/glossary/valve-clearance) regularly so the valves close fully.

## Related terms

- [Valve clearance](https://motorsikletparcasi.com/en/glossary/valve-clearance): Valve clearance adjustment sets the gap between the valve stem and the part that opens it (rocker or bucket) to the value in the manual.
- [Camshaft](https://motorsikletparcasi.com/en/glossary/camshaft): The camshaft uses its cam lobes to open and close the valves at the right time.
- [Cylinder head](https://motorsikletparcasi.com/en/glossary/cylinder-head): The cylinder head closes the top of the combustion chamber and carries the valves, camshaft and spark plug.

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