What size carb should you use in a 80cc 4 stroke moped?

It looks like a curburetor that's between 20mm and 26mm would be in the right range for throat size. A carburetor in that range should be able to feed an 80cc engine properly. Mounting the carburetor is a whole different question, there are a few different types of mounting styles, having and old carb to match up with would be the best way to go. Marty S.