Grand Pops 1810: I think that the "26" and the "30" refer to diameter of the carb throat in millimeters; that is, the 30 carb has a 30mm throat and the 26 carb has a 26mm throat.
Personally, I'm surprised to learn that my 18 HP twin cylinder engine uses a smaller carburetor than my 14 HP single cylinder; but I trust the people telling me.
