The three blades and ball bearing typically fall out when turned over. Note the assembly in the picture above is wrong - the blades each have a beveled edge that follows the curve of the bore. This unit must have been "serviced" before. A suggestion prior to disassembly is to spray oil all over this stuff, then gently pull it all out. Make sure you catch the little bearing. Note the air input side has a metal "air filter" (a screen which is typically filthy), a spring that is smaller on one end than the other, and under the spring it should have a gauze pad soaked in oil.
It works like this: When the rotor spins the blades are forced against the bore. Air is drawn through the metal filter and over the oiled gauze into the air chamber, where it is compressed as the rotor turns. The oiled pad serves to lubricate the rotor. At the smallest point of the bore, the chamber just before the metal filter, air is expelled into the brass nipple leading to the air horns.
The important bits:
- The exterior housing is typically filthy. Clean it thoroughly before disassembly. We used a can of carb cleaner and a brass brush on a dremel tool. On low speed it does not mar the aluminum
- Use carb cleaner to spray through the mesh filter until you can see through it. If you don't have that filter then you can make one from a piece of brass or plastic insect screen
- The gauze is probably junk by now - we replaced it with cotton medical gauze. You can use a bit of a t-shirt or towel.
- The aluminum FIAMM used must have originally been coated with something but after you clean it up it will oxidize in about 2 minutes. We used a very light coat of aluminum colored caliper paint to seal it.
- There is a plastic plug in the side of the unit. You can use electric motor / electric contact cleaner in a spray can to clean it out and drain it. We sprayed a bunch in there until what flowed out wasn't carbon colored. We couldn't get the motor out otherwise and didn't want to force it and risk breaking the plastic base.