Fuel will already be broken up into droplets by the time it's being sprayed and the rich mixture jet can be aimed at the spark plug, ensuring reliable ignition. The resulting flame front can then easily burn areas of leaner mixture. Engines using an electronic injection-stratified charge system are available, but at a price. Enter Piaggio's greatest stroke of genius since introducing the Vespa. The engine's bottom end is a regular clean burning two-stroke that pumps in clean air that will be transferred to the cylinder through the ports.
Incoming air is throttled by one of the bores in a special double barreled carburetor.
This half of the carb doesn't have any fuel jets, it only flows clean air. The real action happens in the cylinder head where a tiny crankshaft drives a small piston. On its downward stroke it compresses the rich mixture to about 70 PSI at which time the rising pressure raises a spring loaded poppet valve off its seat and the charge is squirted into the cylinder. There it is aimed at the spark plug area and ignited. The pumping piston has to be timed to work with the cylinder, though the exact moment for injection is controlled by the poppet valve's spring preload.