This is the diagram found on the air box.
The air system consists of these main parts:
- two air solenoids
These are commanded by the PGM IV to either open or close. I haven't been able to find out whether they are commanded to open at the same time or whether the PGM IV unit first opens one and if more air is needed, then the second one. They are not parallel wired so I assume they are controlled separately.
- Sub-air filter
The air to the carburetor main emulsion tube is drawn through this little filter sitting in the r/h underside of the airbox. It is two stage, one coarse and a fine paper filter.
- Loads of tubing and some connector
Note that the 4-way connector has a "dead end" with a plug. This plug does not seem to have a function except one could measure the vacuum at various operating conditions if a vacuum meter was attached instead of the plug.
This is how it works:
(1) If the air solenoids are not commanded by the PGM IV to open, the carburetors draw the air to the main jet emulsion tube through the 4 way connector directly from the sub air filter. There is a < 1 mm brass jet in the passage to the sub air filter in the 4-way connector whichprecisely limits the air drawn this way.
(2) If one or both air solenoids are commanded to open (by powering them with 12V), additional air flows through the solenoids to the carburetors.
