Huh? You don't have any main jets? :-D
Them main jets are not "in the float bowl". The mains in a Mikuni carburetor are screwed into the carburetor body inside the float bowl but above it, but not to the float bowl. They look like a little brass screw in the dead center, where the slide needle can come down through it. (so to speak) I'm guessing you should have a 125-120-125 set on your carbs ( That is, 125 on the outside carbs, and 120 on the center carb. It should be marked on the face of the main).
They are about the size of a pencil eraser. They may also be a 130-125-130 which is the best jetting for a T300 Speed Triple, or if they are a dynojet set they could be quite different.
The pilot jets, or "air jets" will be marked 40 and are offset from the center of the carb body. Don't change these.