Removing the hex nut that secures the air valve assembly can be difficult. A thin walled 7/8" socket or one that has been ground off slightly to clear the air vent tube is a good wrench to use.

Secure the carburetor body in a sturdy vise and attach a pull handle to the socket. If it does not want to loosen, you may have to wait till it has soaked in the cleaning solvent for a day. Many of these nuts were damaged because poorly fitting open end wrenches were used and they simply rounded off the soft brass edges on the nut.

The hex nut contains a chamber that holds the air valve spring. The air valve rides on the spring, which keeps the air passage closed until the suction is sufficient to overcome the spring tension. The spring performs an important function in the operation of the air valve. If it appears weak or damaged from rust or deterioration, replacement is advised.