No i didn't take the disc valve off, I tried but it didn't want to come off . It has a tight fit and feels overall ok. O-rings have also been replaced.

Anyway, do you have any ideas what a worn piston/liner can cause? Isn't the regulator somehow linked to the crackcase pressure (which I think wont be normal if there is leaking between piston and cylinder liner)?

Apparently the intake valve has also hit the piston, could the valve be bent or something...? Is the any way to see if it's leaking when closed?

Thanks
Ezanen