Carbs
How far did you take the carbs apart? If the bike won't run with the choke off, there is a fuel starvation issue (most likely)
Either the carbs aren't clean, a mistake was made upon reassembly or the fuel supply to the carb is restricted in some way. Needle valve set to specs?
The best way to get the gunk out is get the entire fuel system clean. Is the tank rusty? Is the fuel petcock clear? Is there an in line fuel filter? If you start the bike and it runs with choke only....problem is in the carb most likely.
You have to fully disassemble the carbs and soak them in a good carburetor cleaner for two days or more.
By good carb cleaner I mean the kind that comes in a 3 to 5 gallon pail with a sinkable parts tray.
After soaking and cleaning you must make sure all passages and "jets" are free of obstructions. Compressed air and a little oil tells all. Any plastic or rubber parts you forgot to remove will be melted.
The idle passages are often smaller and harder to clean out. I found out the hard way, on more occasions that I care to admit, that a short cut or an assumption about a passage being clear will bite you in the butt.
Check, clean, inspect every inch of that filthy little carb before reassembly.
Buy the new gaskets and o-ring set, Replace the float needles and seats
Make sure you have the floats in right and the float bowls right when you assemble.
If the tank has rust, I use a bunch of steel balls that came out of a silver tumbler.
Best of luck.