A two-stroke spark-ignition engine with through scavenging, exhaust valves (7), an injection nozzle (5) and sparking plug (6) in the cylinder head is characterized by higher volume efficiency and higher volume output with the possibility of gradual change of timing of air inlet into the engine cylinder (2) from the idle run to the full power. The use of a charger or turbocharger is convenient. Higher volume efficiency is achieved by a limitation of flow of exhaust gas back to the suction part through a gradual change of the inlet section to the engine cylinder (2) and by ensuring a higher air pressure before the inlet section. The change of the inlet section is achieved by a rotary bushing (4) on the cylinder (2) or insert of the engine cylinder (2), the bushing (4) being controlled with a control rod (14) from the throttle pedal.