To compensate for the fuel, richer jets are required. Let a freshly oiled air filter dry at least 6 hours in advance so that the alcohol in the air filter can evaporate. Then match the carb to a motor that breathes properly. Otherwise, the engine will run slightly leaner when the clean air filter is installed. When performing a plug check, use a good used spark plug.
New plugs are white and are hard to read accurately for mixture checks.
If you have to use a new plug be sure to put at least 15 to 20 hard minutes on it before attempting to get a reading. Always check for clogged carb vent lines. Clogged lines will cause hard starting and bogging when the motor is hot. They can also cause erratic running that seems to mimic a mis-adjusted float, but worse. Performance will seem rich and acceleration will be sluggish off idle.