A handheld engine-driven working machine comprises an internal combustion engine with a throttle valve, a throttle adjusting device for adjusting an opening degree of the throttle valve of the internal combustion engine, and a control device provided in the internal combustion engine. The control device is configured to detect a rotational speed and an amount of change in the rotational speed at every at least one rotation of the internal combustion engine. The control device determines that the throttle valve is partially opened when the amount of change in the rotational speed is greater than a predetermined value.

A two-stroke engine piston (1) is disclosed comprising a piston top (3), a mantle surface (5), a stratified scavenging channel (7) in the mantle surface (5), and a weight reduction space (9) arranged between the piston top (3) and the stratified scavenging channel (7). The weight reduction space (9) has a largest first axial extent (a1) at the mantle surface (5) and a second axial extent (a2) radially inside the mantle surface (5), and wherein the second axial extent (a2) is greater than the largest first axial extent (a1). The present disclosure further relates to an engine (30), a hand-held tool (40), and a method of manufacturing an engine piston (1).

A two-stroke engine piston (1) is disclosed comprising a piston top (3), a mantle surface (5), a stratified scavenging channel (7) in the mantle surface (5), and a weight reduction space (9) arranged between the piston top (3) and the stratified scavenging channel (7). The weight reduction space (9) has a largest first axial extent (a1) at the mantle surface (5) and a second axial extent (a2) radially inside the mantle surface (5), and wherein the second axial extent (a2) is greater than the largest first axial extent (a1). The present disclosure further relates to an engine (30), a hand-held tool (40), and a method of manufacturing an engine piston (1).

The invention relates to a method for operating a work apparatus having a combustion engine. An ignition device is provided for triggering an ignition spark at a spark plug for igniting a fuel/air mixture in a combustion chamber of the combustion engine. The combustion chamber is bounded by a piston which drives a crankshaft in a rotating manner. In order to avoid the combustion engine stopping in rich mode, the speed (n) of the combustion engine is monitored over the period of time (t, ΔT) and the ignition point (ZZP) of the ignition device is advanced if the speed (n) of the combustion engine lies within a predefined speed range (n.sub.min; n.sub.max) within a predefined period of time (t, ΔT) and then the speed n drops below a speed limit value (n.sub.G).

A backpack type blowing apparatus includes an intake pipe that connects an air cleaner fixed to a fan case of an air blower to a carburetor that supplies an evaporated fuel to an engine body, and a top cover fixed to the fan case to cover at least the intake pipe by interposing the intake pipe between the top cover and the fan case. The top cover has a plurality of cover fixing portions fixed to the fan case. An outer circumferential-side fixed portion positioned on an outer circumferential side of the intake pipe in the fan case is included in the plurality of cover fixing portions.

An air-leading type, stratified scavenging two-stroke engine. The engine including a cylinder member and a crankcase joined therewith has an intake passage, an exhaust passage, first and second scavenging passages, a communicating portion and an air passage. The intake passage, the exhaust passage and the air passage are formed in the cylinder member. The first and the second scavenging passages each has a cylinder member-side passage and a crankcase-side passage. The cylinder member-side passages of both of the first and the second scavenging passages communicate with each other via the communicating portion. The air passage is connected to the cylinder member-side passage of the first scavenging passage. In the engine, air for pre-scavenging is introduced from the air passage through a check valve into the cylinder member-side passage of the first scavenging passage, and a part of the introduced air flows into the second scavenging passage through the communicating portion.

An engine-driven working machine including a controller by which a time period until the rotation speed limitation mode is canceled can be shortened. After a throttle valve is moved to a fully-closed position by an operation to allow the engine to finish the fast idling state and while the engine is transited to an idling state, the controller cancels the rotation speed limitation mode by detecting an event in which a cycle period of rotation speed variations of the engine is longer than a cycle period of rotation speed variation in the fast idling state.

An engine-driven working machine including a controller by which a time period until the rotation speed limitation mode is canceled can be shortened. After a throttle valve is moved to a fully-closed position by an operation to allow the engine to finish the fast idling state and while the engine is transited to an idling state, the controller cancels the rotation speed limitation mode by detecting an event in which a cycle period of rotation speed variations of the engine is longer than a cycle period of rotation speed variation in the fast idling state.

The present invention discloses an engine oil pan, which includes a cylinder block, wherein a plurality of arc-shaped grooves are disposed on the second end surface of the cylinder block along the axial direction of a crank shaft; the arc-shaped grooves form arc-shaped bulges in a sunk portion on the first end surface of the cylinder block; the arc-shaped bulges divide the sunk portion into first space and second space; a platform is disposed inside the sunk portion of the cylinder block; and the height of the platform is lower than the height of the arc-shaped bulges. The technical solution employed by the present invention enables lubricating oil in the engine oil pan to flow more effectively, and enables the lubricating oil in the oil pan to be utilized more effectively when the engine is used in any position.

A stratified scavenging two-stroke engine includes: an intake passage that connects an intake opening through an outer surface of a cylinder member with an intake port opening to the inside of a cylinder, and supplies gaseous mixture of fuel and air; an exhaust passage that connects an exhaust outlet opening through the outer surface of the cylinder member with an exhaust port opening to the inside of the cylinder, and discharges combustion gas; a scavenging passage; and an air passage that connects an air inlet opening through the outer surface of the cylinder member with the scavenging passage and supplies pre-scavenging air into the scavenging passage. The intake and the air inlet are arranged at positions opposite from the exhaust port across the axis of the cylinder, and arranged side by side in a substantially circumferential direction of the cylinder or a direction substantially perpendicular to the axis of the cylinder.