imported post
This is an excerpt from the GL1800 manual I have. It's a pretty good explanation and pretty much the same for all of the Goldwings that have this system.
Secondary Air Supply System
The secondary air supply system introduces filtered air into the exhaust gases in the exhaust port. Fresh air is drawn into the exhaust port by the function of the Pulse Secondary Air Injection (PAIR) control valve. This charge of fresh air promotes burning of the unburned exhaust gases and changes a considerable amount of hydrocarbons
and carbon monoxide into relatively harmless carbon dioxide and water vapor.
The reed valve prevents reverse air flow through the system. The PAIR solenoid control valve is controlled by the PGM-FI unit, and the fresh air passage is opened and closed according to the running condition (ECT/IAT/TP/MAP sensor and engine revolution).
No adjustments to the secondary air supply system should be made, although periodic inspection of the components is recommended.
Hope this helps. I think people are getting this system confused with the Intake manifold SHOT Air System. (see below... From the GL1500 manual.)
INTAKE MANIFOLD SHOT AIR (DECEL COMPENSATION) SYSTEM.
Due to the large 1500 cm3 engine displacement and the fact that the valve timing has a small intake/exhaust overlapping, the
compression braking effect during deceleration is strong.
The shot air system has been incorporated to moderate compression braking and improve riding comfort.
The shot air system supplies air to the intake manifolds during deceleration to prevent sudden induction of strong manifold
vacuum.
As illustrated, the intake manifold vacuum acts on the lower diaphragm chamber of the shot air valve through No.1 and No.2
tubes. When vacuum rises during deceleration, the diaphragm is pulled down to allow air from the air cleaner to enter the intake
manifolds.
To ensure a natural deceleration feeling when the engine is revved up and down with the transmission in neutral, the solenoid
valve (Neutral) opens the vacuum route to the upper chamber of the shot air valve when neutral is detected by the gearshift
sensor. Under these conditions, the shot air valve remains closed.
Engine rotation per minute is detected by the pulse generator and signals are transmitted to the carburetor control unit via the
ignition control unit. The solenoid valve 2 opens when engine speed is above 2,000 min-1 (rpm) to increase air supply. In addition
to air through No.7 tube, air flows through No.6 tube, solenoid valve, and No. 10 tube.
The one-way valve is provided in the three-way joint near the intake manifolds. The one-way valve prevents manifold
pressure interference.
If you'd like I can post the relevant pages with the diagrams to make this a little clearer. But I'm sure you've noticed the tubes going from the reed valves to the head. The other openings attach to hoses that go up to the airbox to draw the filtered fresh air supply.
.
