RE: Homelite 33cc
"28" in the carb throat means a venturi size of 28/64". 64 divided by 28 equals .4375". .4375" x 25.4 equals a venturi size of 11.11 mm. It is an 11mm carb. It would probably run a bit better with a 12.7mm carb, which would have a "32" casting number in the carb throat. This would especially be true if you are running a smaller prop. If you want to run as large a prop as possible for your application, it might do just as well with the 11mm carb, but only experimentation would tell.... I suspect the 12.7 carb would be better for most applications.
AV8TOR