Hi Paul, can you tell us the model of Shindaiwa concrete saw please, and post a couple of pictures?

I'm not clear on what you are saying here. From the symptoms, it sounds as if you may have reversed the connections of the hoses running to the carburetor. In the basic HDA, there are only two hoses: fuel supply and crankcase pulse hoses. If you reversed these, the primer bulb sucks air from inside the crankcase instead of sucking fuel. See diagram:
[Linked Image]

Because your HDA sounds as if it has an air purge pump, you may have three hoses (fuel, crankcase pulse, and air return) or the crankcase pulse connection might be directly through the carburetor mounting flange. The same potential problem applies though: if you interchange the fuel supply and return hoses, no fuel will be picked up from inside the tank, because the fuel return hose is positioned above the level of fuel in the tank, so the only thing it can suck (if inadvertently connected to the fuel connection on the carburetor) is air.