Power valves not closing EC 125
 

Anyone know why the power valves doesnt retract on the EC 125? It is not same as the 300 so keep that in mind.
I have attached a link where you can see how they close and not.
When I open them fully, they dont retract, but if you give it just a slightest push, it goes back.
Later in the video you can see that when I open them just a tiny bit, they close.
So to conclude, when opening fully, they dont retract. When opening a tiny bit, they do.
https://streamable.com/ya90za
Thanks in advance

It is usually carbon deposits jammed in the bore/valves and the little tracks they slide in

Okey thanks for the answer!