![cover image](https://wikiwandv2-19431.kxcdn.com/_next/image?url=https://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Desmo_photo.jpg/640px-Desmo_photo.jpg&w=640&q=50)
Desmodromic valve
Reciprocating engine valve actuation mechanism / From Wikipedia, the free encyclopedia
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A desmodromic valve is a reciprocating engine poppet valve that is positively closed by a cam and leverage system, rather than by a more conventional spring.
- In general mechanical terms, the word desmodromic is used to refer to mechanisms that have different controls for their actuation in different directions.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Desmo_photo.jpg/640px-Desmo_photo.jpg)
The valves in a typical four-stroke engine allow the air/fuel mixture into the cylinder at the beginning of the cycle and exhaust spent gases at the end of the cycle. In a conventional four-stroke engine, valves are opened by a cam and closed by return spring. A desmodromic valve has two cams and two actuators, for positive opening and closing without a return spring.