I don’t see how that piston could work. On the back stroke to let air in the o ring would slide back to the disc with holes and on the compression stroke it would slide to the solid disc. Looks like it would block holes on the intake stroke.
I would like to purchase two of these completely assembled... if possible. My eyes are too far gone to assemble. Can you provide 2 completely assembled units? Please advise with price for 2 units... Thanks!