I guess I'm out of ideas. Wish I could see it.
I did disconnect the muffler as I thought that could be an issue and it didn’t make a difference. Yes the exhaust value is opening and closing I checked that when I removed the valve cover.Did you unhook the muffler to see if it plugged, You said it was pushing air out of the carb instead of drawing fuel. Is the exhaust valve opening up?
make sure there is no water in petrol and try premium petrol i have ride on mower that wont work with non premium petrol