Kohler CH22 starving for gas

I have owned this 62" mower for 20 years. Suddenly, the fuel filter is empty and the mower shuts down - as if I turned the key off. Let it set and the fuel filter {Vacuum} refills to 50 to 75% with the mower off. Restart and it may run for 30 minutes or 2 or 3 hours (it decides). Here is what I have done: Replaced fuel pump (twice), replaced fuel filter, replaced all fuel lines including the rubber grommets on each saddle tank (the pick up hose in the tanks are new), blew out the 90 degree elbows on each tank, new tank selector switch, new breather valve (flapper) & gasket, rebuilt carb and new gaskets, verified governor settings, gas tank cap vents are clear, tanks are clean, new spark plugs, new coils and the compression test were 123 & 125 PSI. I don't think I left anything out. Mower starts great. It mows great (62" deck). You start mowing with a fuel filter 50 to 75% full. 15 minutes later, you see NO visible gas in the filter.....after which it will shut down at any time. It may last 15 minutes....1 hour or 2 to 3 hours. My yard takes 5.5 hours to complete under normal conditions. What am I missing??? I have re-inspected all the new fuel lines, been through 2 new fuel pumps, rechecked the gaskets on the manifold and carb, re-inspected the rebuilt carb, fittings are tight, hoses were new and feel snug. Any suggestions?

What fuel filter are you using? And how did you verify the vents are working properly?

Scrubcadet10 said:

What fuel filter are you using? And how did you verify the vents are working properly?

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The filter was purchased at our areas go-to equipment dealer. I don't recall the exact make. I used a wire and air hose to verify the vent holes were open. I have also loosened the tank cap, as I was mowing, to see if it would increase the gas flow in the filter - which it did not.

Shuts down as if you turn off the key doesn't sound like fuel issue to me. Loss of fuel issue normally will spit and sputter a few seconds before actually dying. Issue to me thinks more of a loss of spark issue. Does this engine have the oil pressure switch which could be faulting out and causing the engine to shutdown.

Compression is below the 160 minimum that Kohler suggest, which may not be a cause but could be a symptom of something else.