An internal combustion engine for driving a working assembly with a clutch, including a combustion chamber into which a mixture of fuel and air is supplied, a spark plug to ignite the mixture, ignition of the mixture driving a piston operably coupled to a crank portion of the engine, a fuel supply system including a fuel valve and a throttle valve, a throttle position sensor configured to determine a position of the throttle valve, a speed sensor configured to determine engine speed, and an electronic control unit configured to control operation of the fuel valve and the spark plug, the electronic control unit being configured to initiate a speed limitation operation in response to a first position of the throttle valve at engine start-up, wherein the speed limitation operation continues until the throttle valve is moved from its first position.

A rim-type abrasion cutter drive sprocket (24) for driving an abrasion cutting chain (16) of an abrasion cutter (10) comprises a set of sprocket teeth, which extend radially away from the drive sprocket's rotation axis (A), and define drive link gaps between them for receiving and drivingly engaging with drive links (26) of the cutting chain (16), and a pair of rim edges (44) which are concentric with and extend about the rotation axis (A) on either side of the drive link gaps, the rim edges (44) being configured to radially support side links (28) of the cutting chain (16). The rim edges (44) have a non-circular envelope, as seen along the rotation axis (A).

A rim-type abrasion cutter drive sprocket (24) for driving an abrasion cutting chain (16) of an abrasion cutter (10) comprises a set of sprocket teeth, which extend radially away from the drive sprocket's rotation axis (A), and define drive link gaps between them for receiving and drivingly engaging with drive links (26) of the cutting chain (16), and a pair of rim edges (44) which are concentric with and extend about the rotation axis (A) on either side of the drive link gaps, the rim edges (44) being configured to radially support side links (28) of the cutting chain (16). The rim edges (44) have a non-circular envelope, as seen along the rotation axis (A).

A power working machine comprises a working portion, a driving portion, a main body portion, and a blowing portion. The working portion is configured to act on a work object. The driving portion is configured to drive the working portion. The main body portion includes a bottom surface portion, an intake port, and an exhaust port, and is configured to form a storage space for storing the driving portion and an airflow path leading from the intake port to the exhaust port through the storage space. The blowing portion is configured to generate an airflow in the airflow path toward the exhaust port. The intake port is configured to open in a direction having a vertical downward component in a first state in which the power working machine is placed with the bottom surface portion facing a horizontal surface.

A simple configuration is provided to facilitate removal of a battery. An electric working machine comprises an electric working portion and a main body portion. The electric working portion is configured to operate by electric power supplied from a battery. The main body portion includes a battery holding portion having a holding space for inserting the battery in an insertion direction and holding the battery. The battery holding portion includes a plurality of openings including a first opening through which the battery passes when inserted and a second opening provided at a position that is separated from a front end of the battery held in the holding space in the insertion direction.

A simple configuration is provided to facilitate removal of a battery. An electric working machine comprises an electric working portion and a main body portion. The electric working portion is configured to operate by electric power supplied from a battery. The main body portion includes a battery holding portion having a holding space for inserting the battery in an insertion direction and holding the battery. The battery holding portion includes a plurality of openings including a first opening through which the battery passes when inserted and a second opening provided at a position that is separated from a front end of the battery held in the holding space in the insertion direction.

Saw systems are provided. A saw system includes a body and one or more interchangeable saw cartridges. The body includes a prime mover and a transmission element. Activation of the prime mover drives the transmission element. Each of the one or more interchangeable saw cartridges includes a saw blade and is interchangeably connectable to the body. The connection of one of the one or more interchangeable saw cartridges to the body causes the saw blade of the one of the one or more interchangeable saw cartridges to be drivable by the transmission element.

Saw systems are provided. A saw system includes a body and one or more interchangeable saw cartridges. The body includes a prime mover and a transmission element. Activation of the prime mover drives the transmission element. Each of the one or more interchangeable saw cartridges includes a saw blade and is interchangeably connectable to the body. The connection of one of the one or more interchangeable saw cartridges to the body causes the saw blade of the one of the one or more interchangeable saw cartridges to be drivable by the transmission element.

An electric tool includes a drive structure, a motor, a driver circuit, and a controller. The controller is configured to output a first control signal to control the motor to drive the drive structure to operate in a first operation mode for a preset period of time in response to receiving a start instruction. After the preset period of time, the controller will output a second control signal to control the motor to drive the drive structure to operate in a second operation mode to a preset state. The first operation mode and the second operation mode are two opposite operation modes.

An electric tool includes a drive structure, a motor, a driver circuit, and a controller. The controller is configured to output a first control signal to control the motor to drive the drive structure to operate in a first operation mode for a preset period of time in response to receiving a start instruction. After the preset period of time, the controller will output a second control signal to control the motor to drive the drive structure to operate in a second operation mode to a preset state. The first operation mode and the second operation mode are two opposite operation modes.