The jet air system is used on models from 1978 on.
A jet air passage is provided in the carburetor, intake manifold, and cylinder head to direct air to a jet valve, operated simultaneously with the intake valve.
On the intake stroke, jet air is forced into the combustion chamber because of the pressure difference between the ends of the air jet passage.
This jet of air produces a strong swirl in the combustion chamber scavenging the residual gases around the spark plug.
The jet air volume lessens with increased throttle opening. It is at a maximum at idle.
Refer to Valve Lash Adjustment for adjusting jet valve clearance.
No maintenance is required, other than clearance adjustment during valve adjustment. The valve can be removed from the cylinder head for service or replacement.