Unplug the fuel line from the carburetor and check fuel flow from the tank. Also, loosen the cap to rule out a plugged cap vent hole. It wouldn't hurt to empty the tank and look inside for debris or a screen.
That's a link to a file on your PC; not useful...file:///C:/Users/USER/Downloads/carburetor_cleaning.pdf
All you need to look at are pages 26 to 35. That's the entire BB Type Carb GCV section.I had also seen the 300+ page online document, which does have a pretty good troubleshooting flow chart.
I found this much shorter Honda Job Aid document regarding cleaning the GCV carbs which seems to be the most succinct:
That is fine for a GX engine carburetor, but there are many types of Honda carburetors... Each section of this document is for a different type/application. Pages 26 to 35 are specific to the BB Type Carb on the GCV engines.