I don't understand your description of the hose arrangements, Paul. I think we are going to need pictures that show the four hoses, how they connect to the carburetor, and where they go to. If you can't get Firefox to work for picture uploads, perhaps one of the other browsers will work better. Alternatively, you could upload your pictures to one of the photo-storage sites and post the references here.
Are you sure you used the correct kit for your overhaul? It appears you need a D20-HDA kit.
Did you follow the manual precisely when you overhauled the carburetor? Here is the manual:
http://www.walbro.com/media/21886/HDAseries.pdf
