Thanks for the post Bobby,

As long as the Piston Ring wasn't damaged when you installed it (this can easily happen if you're not careful), I would say the only other reason you would get such low pressure would be if the Reed Valves are defective. Make sure the Reed Valves aren't cracked, damaged or rusted shut and that they have some "spring" in them when you lift it up. These flappers should open and close easily to create compression.

Confirm the seal with the Piston Ring and Cylinder Wall; can you see any gap between when you manually move the Piston up and down in its stroke? There should be no gap at all, the seal should be pretty tight. I know it's a new kit but I would check just to confirm.

Also, make sure you have no major leaks anywhere (drain valve, any air fittings and connections).

Do you get any air coming OUT of the air intake side of the head? Make sure you're getting suction and that no air is bleeding out of the intake.