Air Venturi Compressor Won't Build Pressure

Same Aliexpress- Found page with the plug that holds bottom valve & scrolled down-tried linking but No bueno-Why I had several pics of same will try to re-locate for you- says their for Yong Heng but solid(not split)aliexpress.com/item/32947532623.html?spm=a2g0o.detail.1000014.3.71df419cN34dQc&gps-id=pcDetailBottomMoreOtherSeller&scm=1007.13338.128125.0&scm_id=1007.13338.128125.0&scm-url=1007.13338.128125.0&pvid=a1200502-e469-4929-98fb scroll down page
 
Sounds like you found the culprit. Did you get any photos of the broken one, which I think is the large valve? If you have any pitting on the seat #14 you can remove it with 400 grit wet or dry and then switching to some 1200 grit on a hard flat surface working the seat in a circular motion. The 1200 also works well to shine up the valves if they have some deposit that don't wont to come off. If it fails to compress like you want after replacing those valves at least you know they are good then I would change the high pressure seals by just removing the four bottom screws and removing the upper cylinder as one piece. You can also turn the fan to get the piston as high as possible to make it easier to remove and install the seals. If you decide to go with the aliexpress split rings keep using the thin springy spacer but use a pair of needle nose to hold the gap in the rings together and then slowly and carefully work the cylinder back over each seal. You'll notice how much tighter it is going on.

jking
 
Jordan G (Pyramyd Air)

Jan 24, 15:35 EST

I just ran out of the my spares I have here that I use. we are expecting parts to come in about a week or so. 

Pyramyd Air

Got this from Jordan yesterday- so will order these (original factory) & also try some from Aliexpress.Will probably put back together with just new valves & see if I get good pressure- just hate to do it twice LOL. 
 
Now I'm REALLY scratching my head- replaced both valve plates & put back together to check while waiting on new rings & now I have ZERO pressure ! WTF! Even with one broken plate & 1 carboned up, I was getting 1500 on line pressure.Got to be major leak somewhere so will tear apart & replace all seals. Any other thoughts?

I think you have installed the reed valve plates in the wrong orientation. I have made this mistake once on my Yong Heng. 
 
Here are the valve orientations

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