You have cleaned the fuel tank and the carburetor, and you have the float chamber working properly. Did you clean out the fuel line from the tank to the carburetor? That will have been full of crud too.
The white smoke may have been unburned fuel, due to prior attempts to start it. You also have a lot of fuel in the muffler, left over from the flooding situation. If that is the story, a few more attempts at starting might lead to it gradually clearing its throat and running better/longer. If that doesn't happen, cleaning the muffler and exhaust port may help. If neither of those helps, you should still check that ignition timing: where is the flywheel, compared with top dead center, when it fires?
I think you are getting closer to success Pete, but you need to get it running steadily to be able to tune it. Meanwhile just use the manufacturer's starting point for mixture adjustment. We don't know whether there are any assembly problems in the carburetor, so the first focus is to see if it will run continuously so you can experiment with the mixture. If you can get to where it is running and you are turning the mixture control looking for the sweet spot, you are on the verge of success.
