Abstract: The starting of an i.c. engine usually takes place by carrying out the necessary number of starting attempts with the carburetor choked in order to obtain an ignition. After that, the choke valve (15,23,24) is opened and the engine can be started by making more starting attempts. Thus, the engine does not continue to run when the choke is on. In order to simplify the starting procedure of e.g. a chain saw, the carburetor can be provided with an elastic choke valve. The elastic valve makes the engine start even though the choke valve is closed as the choke valve will yield to the air stream (FIG. 1) and furnish fuel air mixture to the engine. With the engine running, the choke valve can then be opened.

Abstract: The invention relates to a centrifugal clutch with coupling jaws and pressure spring. Usually tension springs are used for the type of couplings which have three jaws. Tension springs have a weak point in their attachment lugs that are in most cases exposed to harder stress than the rest of the spring body. Likewise, the lugs get often indication of fracture during the manufacture of owing to wear. The present proposal aims at getting a higher security against spring breaks by using pressure springs. It is characterized by hole spaces (18,19,29) in jaws (13) and spoke plates (14,15) and by supporting bridges (23) between the spoke plates.

Abstract: When moving the guide bar on a chain saw in order to adjust the chain tension, the following procedure is applied. Through the guide bar runs a shaft (19) having a slot for a screw driver as well as a shape of a cog-wheel (18) on the inside of the guide bar. The hole in the guide bar is the ordinary hole for a tension pin. The cover (11) above the clutch also keeps the guide bar in place and has an oval opening (23) providing accessibility to the above shaft in all its positions. Inside the guide bar, in the saw body, there is a suitable oblong cavity (16) to make room for the cog-wheel part of the shaft. That cavity has on its lower edge the form of a straight toothed section (17) adapted to the cog-wheel part.

Abstract: A chain tension arrangement of a chain saw having a freely displaceable pin (19) in the saw body introduced into suitable hole (21) in the sword (15) and a tension screw (24) in the cover (10) which covers the centrifugal clutch and is included into the attachment of the sword. For the chain tension moment no presetting of the chain tightening arrangement is required. Owing to the shape of the parts those ones get engaged with each other when fitting the cover. Then the chain tightening is effected with a set screw (25) in the cover by means of a simple hand grip and, after that, the sword attachment is tightened.