I worked for Honda when the CVCC engine came out: it was a complicated, but interesting, system. It had 2 intake valves, one in the combustion chamber and a very small one in the 'precombustion' chamber above the main combustion chamber. The 2-bbl carb was not 2-stage, but one rich barrel (11:1) that fed the precombustion chambers and one very lean (17:1) mix that fed the regular combustion chambers. There were also 2 sparkplugs per 'cylinder', one in the regular combustion chamber and one in the 'precombustion' chamber, 2 intake tracts, too.
The way it worked was: the precombustion chamber was timed 3-5 degrees ahead of the main chamber in cam and spark (oh, yeah, it had 2 coils, 2 sets of points, too - some had 2 distributors instead of 8 wires for the 4-cylinder). This little chamber had a port into the main chamber that entered at a very precisely set angle. When the compression stroke was occurring, the precombustion would fire and the rush of gases into the main chamber caused a swirl effect of the rich mixture around the outside edges, near the cylinder walls. Then the regular sparkplug would try to fire the lean mixture, which would get help because the flow of the rich mix was right across the face of the main sparkplug. This implies that the main plugs had to be indexed properly or else it messed up the important flow pattern.
The rich mix around the outside kept the hardware cooler while the larger, leaner charge was burning to push on the piston. The result was more HP for the same amount of gas, but boy, were they hard to tune...