Abstract: An engine control system is disclosed for reducing the hydrocarbon content in exhaust gas from a crankcase scavenged, two-stroke engine in the operating range near idle, with light operator induced engine loading. As operator demand for engine output power is increased, the control system increases the fuel per cylinder delivered to the engine, while restricting the supplied mass of air per cylinder to a value less than or equal to that flowing at unloaded engine idle.

Abstract: Disclosed herein is a two stroke internal combustion engine comprising first and second alternately fired cylinders, first and second crankcases respectively extending from the first and second cylinders, first and second carburetors respectively including first and second air induction passages respectively extending from the first and second crankcases, first and second reed valves respectively affording communications between the first and second crankcases and the first and second air induction passages, first and second throttle valves respectively movably mounted in the first and second air induction passages, first and second idle speed ports respectively communicating with the first and second air induction passages in the respective areas between the first and second throttle valves and the first and second reed valves, and a conduit communicating between the first and second idle speed ports.

Abstract: An exhaust timing control device for a two-cycle internal combustion engine, in which a valve member functioning as the upper edge of an exhaust port that opens into the inner circumference of a cylinder is disposed in the upper wall of an exhaust passage from said exhaust port. A valve hole having an elongated cross-section is opened in the wall of the exhaust passage in the vicinity of the exhaust port, and is formed at an inclination with respect to the axis of said cylinder. The valve member is arranged slidably in said valve hole so that it can be retracted into said valve hole until the leading end portion thereof becomes substantially coextensive with the inner wall surface of said exhaust passage.

Abstract: Two stroke engine having an exhaust port provided with a rotary type timing control valve at the upper portion thereof. The control valve is connected with a centrifugal actuator which is responsive to the engine speed so that the exhaust port is wide open under a high speed engine operation but covered at the upper portion by said control valve under a low speed operation to change the exhaust port timing.

Abstract: A 2-cycle engine having a transfer passage communicating the crank case with the combustion chamber. The transfer passage comprises a first passage and a second passage. The first passage has a long length and a small cross-sectional area for causing a fresh combustible mixture to flow at a high speed. The second passage has a short length and a large cross-sectional area for causing a fresh combustible mixture to flow at a low speed. An exhaust gas recirculation device is provided for recirculating the exhaust gas from the exhaust system into the intake system of the engine.

Abstract: A 2-cycle engine having a transfer passage communicating the crank case with the combustion chamber. The transfer passage comprises a first passage and a second passage. The first passage has a long length and a small cross-sectional area for causing a fresh combustible mixture to flow at a high speed. The second passage has a short length and a large cross-sectional area for causing a fresh combustible mixture to flow at a low speed. The second passage is connected to the crank room via the bypass passage. A normally closed valve is arranged in the bypass passage. The valve is opened when the engine is operating under a heavy load.

Abstract: A two-stroke cycle internal combustion engine wherein the cylinder is provided with spaced inlet ports with an intermediate wall section therebetween and the piston face is provided with a T-shaped guide outstanding therefrom, the center leg of the guide terminating in a face, which confronts the intermediate wall section when the piston is at bottom dead center, the face increasing in width from the outer edge of the guide leg to the root thereof.

Abstract: A two-stroke internal combustion engine has a plurality of transfer ports controlled by the movement of the piston, the transfer ports being at the ends of passages each extending from the interior of the crankcase through the cylinder wall so as to place the crankcase interior in communication with the upper working space in the cylinder above the piston when its associated transfer port is uncovered by downward movement of the piston. Some, but not all, of the transfer port passages are provided with pressure-responsive non-return valves which are lightly spring-biassed towards closed positions in which they restrict the gas flow through those passages, in the direction towards the upper working space in the cylinder, causing the gas flow from the crankcase to travel at increased velocities through the remaining transfer port passage or passages.