always always always start with a compression check, if you dont have the compression, its going to run like shit no matter what jets you put in it.
you need atleast 100 psi to run worth a damn, if you dont have that, send the motor to a builder.
once you know you have the compression, then check jetting but dont waste your time on jetting if you dont know if you have compression. once that checked, and you still feel its jetting
pull out a carb, make sure its clean, make sure jets are clean, make sure both carbs are synced together, make sure you have the tube between the 2 carbs installed, make sure theres no tears in your boots. then look at correcting which jet to buy.