Jet Air System: Operation

Air flows to jet valve through 2 intake openings near carburetor throttle valve, a passage in intake manifold and a passage in cylinder head. The intake stroke pulls air into combustion chamber through intake valve port and jet valve opening. When throttle valve opening is small, a large pressure difference is produced between jet valve opening and jet intake opening as piston goes down.

This causes jet air to flow into the combustion chamber at a much higher speed than it does at large throttle openings. Because the jet valve opening points directly at spark plug, the air stream scavenges gases accumulated in that area. It also produces a swirling action in the combustion chamber, resulting in a longer burn period after ignition.