Compression release

A compression release mechanism works to ease the starting of internal combustion engines by allowing them to spin up to starting speed without having to work against the pumping action of the pistons. It does this through a release valve that is incorporated within the cylinder head that vents the cylinder pressure to the outside atmosphere until the engine has sufficient momentum to overcome it. At that point the valve closes and the ignition is engaged.

Early large displacement motorcycles provided riders with a manual control for this when kick starters were used while later models linked them to the kick lever through a cable for automatic operation.

See also

• Engine braking

External links

• Patent for a compression release mechanism