Does anyone know how the compression release works?

[stay_upright]

the hole type thing in the cylinder to ease starting....

I can understand a 4 stroke has either manual (released after starting) or auto (releases at an engine speed above cranking) but how would a 2 stroke compression release work? Surely it must have some mechanical components to stop the release of air with the engine started...

 

[gasgasman]

It is "controlled" by piston velocity.
While kick starting, the piston is moving slow enough to allow some blow-by.
Once the motor is running the piston is passing by the port at a rate quick enough that there is not enough blow-by to affect the compression.