An internal combustion engine (1) may include a combustion chamber (41) into which a mixture (40) of fuel and air is supplied, a spark plug (50) disposed proximate to the combustion chamber (41) to ignite the mixture (40) by generating a spark such that ignition of the mixture drives a piston (6) operably coupled to a crank portion (12) of the engine (1), a speed sensor (102) configured to determine engine speed, and an electronic control unit (100) configured to control operation of the spark plug (50). The electronic control unit (100) may be configured to initiate a speed limitation operation in response to engine speed reaching a cut out speed threshold and to control ignition timing within an operating band (320) of ignition angles prior to engine speed reaching the cut out speed threshold. The speed limitation operation may include skipping application of sparks. The electronic control unit (100) is further configured to apply a changed ignition angle (330) relative to the operating band (320) for first at least one spark initiated after the speed limitation operation.

An internal combustion engine (1) may include a combustion chamber (41) into which a mixture (40) of fuel and air is supplied, a spark plug (50) disposed proximate to the combustion chamber (41) to ignite the mixture (40) by generating a spark such that ignition of the mixture drives a piston (6) operably coupled to a crank portion (12) of the engine (1), a speed sensor (102) configured to determine engine speed, and an electronic control unit (100) configured to control operation of the spark plug (50). The electronic control unit (100) may be configured to initiate a speed limitation operation in response to engine speed reaching a cut out speed threshold and to control ignition timing within an operating band (320) of ignition angles prior to engine speed reaching the cut out speed threshold. The speed limitation operation may include skipping application of sparks. The electronic control unit (100) is further configured to apply a changed ignition angle (330) relative to the operating band (320) for first at least one spark initiated after the speed limitation operation.

The present invention is to prevent mixing of fresh air and an air-fuel mixture when a throttle valve is fully opened and increase a delivery ratio. A main nozzle (30) is surrounded by a tunnel-like air flow guiding member (52). The air flow guiding member (52) is opened at its front and back sides. A whole amount of fuel discharged via a main nozzle (30) is sent to a downstream side by an air flow created by the air flow guiding member (52). When a throttle valve (22) and a choke valve (24) are both in a fully-opened state, fresh air flows into an air-fuel mixture passage (12) through a gap between these valves (22, 24).

The present invention is to prevent mixing of fresh air and an air-fuel mixture when a throttle valve is fully opened and increase a delivery ratio. A main nozzle (30) is surrounded by a tunnel-like air flow guiding member (52). The air flow guiding member (52) is opened at its front and back sides. A whole amount of fuel discharged via a main nozzle (30) is sent to a downstream side by an air flow created by the air flow guiding member (52). When a throttle valve (22) and a choke valve (24) are both in a fully-opened state, fresh air flows into an air-fuel mixture passage (12) through a gap between these valves (22, 24).

In an air intake-type two-stroke engine 10, an exhaust port 20, a scavenging port 22,etc. are opened and closed by a piston 12. A fuel injection valve 60 is disposed at an upper end portion 24a of a scavenging passage 24. The fuel injection valve 60 is preferably arranged with its axis Lax directed toward the scavenging port 22. The fuel injection timing is set to the latter half of the scavenging process or the latter half of the combustion process.

In an air intake-type two-stroke engine 10, an exhaust port 20, a scavenging port 22,etc. are opened and closed by a piston 12. A fuel injection valve 60 is disposed at an upper end portion 24a of a scavenging passage 24. The fuel injection valve 60 is preferably arranged with its axis Lax directed toward the scavenging port 22. The fuel injection timing is set to the latter half of the scavenging process or the latter half of the combustion process.