Two stroke engine construction

Claim 1

In a two stroke combustion engine of the crankcase compression type, including a cylinder, a piston disposed in the cylinder for reciprocal motion therein, a sealed crankcase, air intake passage means communicating with said crankcase through an air intake port, an exhaust port which is open in the side wall of the cylinder and opened and closed by the piston, at least two main scavenging passages communicating said crankcase with the cylinder through at least two main scavenging ports which are open in the side wall of the cylinder and opened and closed by the piston, said main scavenging ports being disposed symmetrically with respect to a diametral plane of the cylinder passing through the center of the exhaust port, and so directed that the air flows therefrom coverage towards a first point located on a first generatrix of the cylinder diametrically opposite to a second generatrix passing through the center of the exhaust port, an auxiliary scavenging passage of smaller crosssection than that of the main scavenging passages and opening at one end into the cylinder through an auxiliary scavenging port which is opened and closed by the piston and is located substantially opposite the exhaust port and arranged to direct its air flow towards a second point located substantially on the second generatrix, and fuel injection means located in the auxiliary scavenging passage and having its axis directed towards said second point, the improvement consisting in that the auxiliary scavenging passage communicates at its other end with said crankcase at least as long as the auxiliary scavenging port is uncovered by the piston.