S
sprayerman
Get one of those gallon or 5 gallon cans of carb dip with the basket inside, and soak the cap in it overnight. Remove, rinse with water, and blow out with compressed air. This will usually do the job. Sometimes welding tip cleaners might be required, but they have to be used very carefully because they can damage the air cap.
P.S. Use heavy gloves and face protection when dealing with the carb dip, it is seriously nasty stuff!
Sorry for the late reply been away. Much appreciated for the tip!