Compression release
Encyclopedia
A compression release mechanism works to ease the starting of internal combustion engine
s by allowing them to spin up to starting speed without having to work against the pumping action of the piston
s. 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 start
ers were used while later models linked them to the kick lever through a cable for automatic operation.
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...
s by allowing them to spin up to starting speed without having to work against the pumping action of the piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s. It does this through a release valve that is incorporated within the cylinder head
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder, forming the combustion chamber. This joint is sealed by a head gasket...
that vents the cylinder pressure to the outside atmosphere until the engine has sufficient momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
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 start
Kick start
Kick start refers to a method of starting an internal combustion engine by pushing a ratcheting lever with one's foot. Kick start mechanisms were almost universally a part of motorcycle engines before the mid-1970s, and were phased out of production over the next twenty years or so as electric...
ers were used while later models linked them to the kick lever through a cable for automatic operation.