Thanks for the responses.
I'm using OEM rebuild kit. There are two springs included; one gold and one silver. The sliver is about a 16th longer than the gold. The carbs had the gold in them, and I don't believe have ever been rebuilt. So, it's definitely gold, not silver or black, and pops off around 20-22, not 55 as the spec says. Now, due to missing parts (the two plastic check valves are missing from both kits) and incorrect parts list/diagram (I think part #3 is described as 'o-ring'), I'm wondering if something is awry. ???
Okay, allow me to unload here comes an info dump:
An original gold spring will give you a pop in the 20psi area if used with a 2.3 or 2.5 seat, but you shouldn't see that low pop pressure release with a 1.5 seat.
Instead, an unmodified/undamaged gold spring with an 1.5 seat orifice should get you very close to 55psi pop-off. If the carb hasn't been rebuilt yet(original unmodified metering arm and spring), then I don't have any suggestion for why your pop occurs at 22psi with a gold spring and 1.5 seat orifice. What is your metering lever arm height, is it just a hair above the fuel chamber bottom? I drag a razor blade across the bottom and if necessary adjust the arm height (gently bend it) until the razor blade just snags the lever arm. If yes, then, if you press the lever arm against the spring fully to the bottom, it should clearly lift the needle off it's seat so that fuel can enter the chamber. Normally, engine vacuum pulls the rubber diaphragm into the chamber, which pushes the lever arm and opens the metering valve. If the metering valve doesn't open with the correct vacuum pressure, there will be a lack of fuel, or vice-versa, if the valve doesn't seal in the seat, there will be too much fuel. This is a fuel on demand design (demand is engine vacuum) and has most of it's effect at idle and low throttle position, when set up properly. I usually go for the low end of pop range, to avoid throttle lean spots (excessive fuel lag).
The missing check valves are made of a mylar plastic film which is cut from a large sheet and was rolled up in a roll at the plastics manufacturer, so they probably will have some natural curvature built into them, and you need to install them in the correct orientation(ie: not flipped upside down) else they may not seal well.
Sometimes people will unknowingly change the metering spring with the wrong one provided in the kit or while trying to measure pop, even modify the spring by cutting or stretching it, which can cause the wrong pop, or inconsistent pop at best. Any combination of the parts will give results close to those in the chart.
Anyway, the pop spec is defendant mostly on the airbox/flame arrestor design, some are more restrictive than others thus the pop is set accordingly. Aftermarket air filters will most likely require complete carburetor recalibration, running the engine at high loads without a flame arrestor can cause a lean-running condition and result in engine damage.
I'm pretty sure I haven't answered your question yet, but we can work through it with a little patience. First, double check you have the correct parts, if one is incorrect (such as the seat orifice) then the results will be incorrect, accordingly. Also, make sure your pop gauge is calibrated, could be it was dropped or damaged and reporting the wrong pressure.
Also, I prefer to use the original spring if possible, usually they are just fine unless someone has tried to modify them. Replacement springs can be a problem occasionally if they are low quality (for whatever reason).
This attached document is the instruction for installing the two missing fuel pump check valve disks:
