Thank you for your useful troubleshooting PDF and upon inspect my carburettor. I found:
1: when following your step outlined in page 16, step 4, when pump bulb 3-4 times, it shows negative pressure, if I pump more, more negative pressure, but also having a very slow gradual decrease pressure as well. Sorry, I just want clarify yours saying “ hold for at least a full second”, mine was drop by 1 every 2-3 seconds, is it normal?
2: when inspect white plastic fuel discharge tube, there is top port, but I also found a side port in the middle section of plastic fuel. It is hard to take photo’s I just draw a red circle from your PDF for demonstration. So is there a side port? Please see photo uploaded.
3: I done all the test, carburetor was fine, fuel intake, pump bulb, fuel return line, vent, the issue is I have to screw all the way on LA screw and my L screw is open only ¼ in order to run at idle at 2800 RPM, if I unscrew L for another ¼ or ½ or even 1 full turn, engine will die.