couple of thoughts .
is the float level right , is it a brass or plastic float , is it adjustable float level or fixed , is the float cracked or damaged making it just sink .
where the needle valve seat and banjo go into the carb they dont have a gasket at that point , it is a face to face contact , but i have seen a few carbs with a gasket there but this will make the float level higher in the carb and possibly just flood all the time if you dont have an adjustable height float .
you can get a "stay up " float kit from amal uk which i think is adjustable for float level .
get some welding nozzle tip cleaners to poke the jets through, they are only about £3 a set . .
my leader was stored in shed for almost 30 years and carb full of treacle , it cleaned up ok but needed 3 times of cleaning the pilot jet before it was starting reliably .
cellulose thinners works well for cleaning the crap out the carbs or for soaking it in .
for some reason my carb had a quite thick cork float bowl gasket on it and when i changed to a new paper gasket it leaked fuel everywhere , then i noticed the bowl cover was not flat but distorted due to it settling down to the thick gasket , so i found another cover which was flat and fixed the problem .
i did find that after cleaning carb and jet out a few times that once it was in a decent state that i didnt need the choke to start engine , and only needed to put a little choke on once the engine had fired .
before when i had first tried starting the bike i used the full choke and think i flooded it most of the time to be honest .
if you have flooded youre engine more than once then you will get fuel down in the exhaust , so what you are seeing is just a result of that and should clear out after a bit .
once youve ran it for while and for a run i expect the smoke will become less , they all smoke when started from cold and need warming up before it reduces .
there is a bit of info in the files section on the yahoo forum about 2 stroke oils and mixes and some other information .
hope you sort it easily