Abstract: The present invention provides a working machine having an internal combustion engine. The working machine includes a single operation unit comprised of a rotatable body adapted to be selectively rotated between an engine-stop position, engine-start position and choke-activation position, a valve to be rotated about an rotation shaft, an arm attached to the rotation shaft and a link member adapted to be moved in its longitudinal direction to transmit the movement of the rotatable body to the arm. The link member has a distal end coupled with the arm and a proximal end coupled with the rotatable body, and extends between the distal and proximal ends. The rotatable body is formed with an elongated slot receiving the proximal end therein. When the rotatable body is rotated from the engine-stop position to the engine-start position, the proximal end is allowed to displace relative to the rotatable body along the elongated slot without causing any movement of the link member in the longitudinal direction.

Abstract: A carburetor is supported on a casing by the air-fuel mixture discharging port thereof and by the portion of the adjustment screws thereof. A first vibration isolating member is interposed between the casing and the air-fuel mixture discharging port, and a second vibration isolating member is interposed between the casing and the adjustment screws. These vibration preventing members prevent the direction transmission of the vibration of the casing to the carburetor side. A reasonable and compact carburetor support structure can be provided because the air-fuel mixture discharging port and the adjustment screws are intrinsically provided with the carburetor itself.

Abstract: A portable power tool includes an internal combustion engine that includes a crankshaft in which a load applied thereto is unevenly distributed along the axis of the crankshaft with respect to the axis of the reciprocating movement of a piston. The portable power tool also includes operational members that are driven by the internal combustion engine, a rotational body fixed to an end of the crankshaft to which a smaller component of the load is applied, and a balancing weight provided on the rotational body for absorbing vibrations generated by the reciprocating movement of the piston. The centroid of the balancing weight is disposed at an angular position from 140 degrees to 180 degrees with respect to the axis of the reciprocating movement of the piston in a rotational direction of the rotational body, when the piston is positioned at a top dead center.

Abstract: A vibration-isolating member is formed of an elastic material, and has a mounting hole at the center thereof, a large diameter section at an end of the mounting hole, a groove at the periphery of the large diameter section, and a flange. One of a vibration-source-side member and a vibration-receiving member is fitted into each of the large diameter section and the groove. An end opposite from the large diameter section is secured to one of the vibration-receiving member and the vibration-source-side member by a mounting member. Since the inside diameter of the large diameter section is larger than any other part of the mounting hole, either of the vibration-source-side member or the vibration-receiving member and the mounting member can be received. The flange prevents the vibration-isolating member from disengaging from one of the vibration-source-side member and the vibration-receiving member.

Abstract: A method of manufacturing a cylinder for an internal combustion engine, which is manufactured by a process wherein a raw cylinder body having an insert core left remained therein is obtained using an insert core comprising a cylindrical body having almost the same outer diameter as the diameter of bore of the cylinder, and a scavenging port-forming portion projecting radially outward from the cylindrical body and having almost the same cross-sectional configuration as that of the scavenging port, the cylinder bore of the raw cylinder body thus obtained is then subjected to a boring to remove the cylindrical portion of the insert core, and the scavenging port-forming portion of the insert core which is left remained in the raw cylinder body is removed by making use of a press.

Abstract: A reciprocating cutter type trimmer having reciprocative blades, each blade is divided into a power transmission member and an edge member, and the edge member has, at its longitudinally opposite ends, fitting parts so as to be removably mountable to a fitting part provided for the power transmission member.