Abstract: A first pinhole is formed in a first member in a section facing a second member. A second pinhole is formed in the second member in a section facing the first member. A connecting pin is inserted into the first pinhole and the second pinhole from the side of the machine center. A coming-off prevention mechanism includes a coming-off prevention lever. The coming-off prevention lever can abut the inner end surface of the connecting pin. The coming-off prevention lever is supported by the second member to be able to move between an abutting position of abutting the inner end surface of the coupling pin and a non-abutting position of not abutting the inner end surface.

Abstract: A boom mount device of a construction machine can easily align a boom with an upper frame of the construction machine when mounting the boom on the upper frame. The upper frame includes a center section including one pair of left-and-right vertical plates. The vertical plates include outside surfaces facing outside and guide parts disposed on the outside surfaces and guide holes are formed. An adapter that pivotably connects a base end of the boom and a base end of a boom cylinder is mounted on the base end side of the boom. The adapter includes one pair of left-and-right guide pins. When the boom is mounted on the upper frame, the one pair of left-and-right guide pins is inserted into the guide holes of the one pair of left-and-right guide parts.

Abstract: A work attachment is capable of performing work at a high place while restricting the driving force required to lift the work attachment from its fallen posture in a folded state. The work attachment includes a main boom, a first insert boom and a second insert boom to be selectively used, an intermediate boom, an arm, and a distal working device. The intermediate boom has bendable first and second joints. The second insert boom has a fixed shape. The first insert boom is bent to project upward at a middle joint in the fallen posture, thereby making the center of gravity of the work attachment closer to a boom rotation center axis.

Abstract: A work attachment is capable of performing work at a high place while restricting the driving force required to lift the work attachment from its fallen posture in a folded state. The work attachment includes a main boom, a first insert boom and a second insert boom to be selectively used, an intermediate boom, an arm, and a distal working device. The intermediate boom has bendable first and second joints. The second insert boom has a fixed shape. The first insert boom is bent to project upward at a middle joint in the fallen posture, thereby making the center of gravity of the work attachment closer to a boom rotation center axis.

Abstract: A carburetor having a main intake passage for a lean mixture and an auxiliary intake passage for a rich mixture is provided with a choke valve in each passage. A control mechanism for operating the two choke valves includes a lost-motion connection so that the main choke valve is at the first to be moved toward closed position, for cold starting of the engine. For colder temperatures, both choke valves are moved toward closed position, and for very cold starting conditions, both choke valves are moved to fully closed position. The control mechanism may be manually operated or it may be automatic under the control of a bimetal element. When the engine on being started reaches a state of complete firing, with stable RPM, both choke valves are opened to predetermined pull-down angles.