Vivo is right on as usual! The universal for float height is inspect and/or adjust so the float is parallel with the carb/float bowl flange. This is with the carb off the engine and upside down. However, your problem may not be float height. It may be a small piece of trash in the float valve seat. Remove carb from engine, remove float bowl, remove float and needle, inspect with magnifier (regardless of age of inspector), remove whatever crud in the seat that presents itself. Reassemble in reverse order. Report back here as to the success of the above operation.
Karl