Abstract: A centrifugal clutch has a clutch drum and a strip therein elastically secured to a clutch center and transfers a driving torque by servo action. During normal torque transfer the strip drives in a pushing manner with servo action. Upon overload its driving point changes onto a shoulder provided with a pressure spring and the torque transfer becomes a pulling action with no servo action.

Abstract: A base structure of a motor saw forms fuel and oil tanks (16,17) and a crankcase bottom in one piece. This piece is injection moulded in plastics with closed tank cavities obtained by means of cores in the mould which are made of a metal having a melting temperature lower than the softening temperature of the plastic material. After moulding the cores are melted by heat treatment and the metal runs out through filling holes (18,19) of the tanks. Armouring pieces are moulded in the plastics to reinforce the attachments of crankshaft bearings and the guide bar.

Abstract: The invention relates to an indicator controlled by the ignition system of an i.c. engine, so that the indicator, e.g. an LED, makes an indication when the engine is adjusted to an appropriate idle r.p.m. or race r.p.m. As the carburetor is calibrated against such selected and adjusted r.p.m. the said adjustment will bring about a minimum of exhaust gases.

Abstract: The bearings of the crankshaft of an internal combustion engine are surrounded by rings of a high temperature resistant polymer, the rings being pressed into bearing seats in the upper and lower portions of the crankcase, the rings being formed with extensions to completely separate the upper and lower portions of the crankcase. The rings enable the use of plastic materials for the lower crankcase, by insulating the lower portion of the crankcase from heat in the upper portion thereof.