Abstract: Crankcase scavenged two-stroke internal combustion engine (1), in which a piston ported air passage is arranged between an air inlet (2) and the upper part of a number of transfer ducts (3, 3?). The air passage is arranged from an air inlet (2) equipped with a restriction valve (4), controlled by at least one engine parameter, for instance the carburetor throttle control. The air inlet extends via at least one connecting duct (6, 6?) to at least one connecting port (8, 8?) in the engine's cylinder wall (12). The connecting port (8, 8?) is arranged so that it in connection with piston positions at the top dead center is connected with flow paths (10, 10?) embodied in the piston (13), which extend to the upper part of a number of transfer ducts (3, 3?).

Abstract: Crankcase scavenged two-stroke internal combustion engine (1), in which a piston ported air passage is arranged between an air inlet (2) and the upper part of a number of transfer ducts (3, 3?). The air passage is arranged from an air inlet (2) equipped with a restriction valve (4), controlled by at least one engine parameter, for instance the carburetor throttle control. The air inlet extends via at least one connecting duct (6, 6?) to at least one connecting port (8, 8?) in the engine's cylinder wall (12). The connecting port (8, 8?) is arranged so that it in connection with piston positions at the top dead center is connected with flow paths (10, 10?) embodied in the piston (13), which extend to the upper part of a number of transfer ducts (3, 3?).

Abstract: Crankcase scavenged two-stroke internal combustion engine (1), in which a piston ported air passage is arranged between an air inlet (2) and the upper part of a number of transfer ducts (3, 3?). The air passage is arranged from an air inlet (2) equipped with a restriction valve (4), controlled by at least one engine parameter, for instance the carburetor throttle control. The air inlet extends via at least one connecting duct (6, 6?) to at least one connecting port (8, 8?) in the engine's cylinder wall (12). The connecting port (8, 8?) is arranged so that it in connection with piston positions at the top dead center is connected with flow paths (10, 10?) embodied in the piston (13), which extend to the upper part of a number of transfer ducts (3, 3?).

Abstract: Crankcase scavenged two-stroke internal combustion engine (1), in which a piston ported air passage is arranged between an air inlet (2) and the upper part of a number of transfer ducts (3, 3′). The air passage is arranged from an air inlet (2) equipped with a restriction valve (4), controlled by at least one engine parameter, for instance the carburetor throttle control. The air inlet extends via at least one connecting duct (6, 6′) to at least one connecting port (8, 8′) in the engine's cylinder wall (12). The connecting port (8, 8′) is arranged so that it in connection with piston positions at the top dead center is connected with flow paths (10, 10′) embodied in the piston (13), which extend to the upper part of a number of transfer ducts (3, 3′).

Abstract: Crankcase scavenged internal combustion engine (1) of two-stroke type, intended for a working tool, preferably a chain saw or a trimmer, and provided with a light-weight and compact muffler (2). The engine is arranged with a particularly high crankcase compression created in that at least one filling (3, 4, 5, 6) is placed into the compression area (7) under the engine piston (8) in form of a filled balance (3) and/or a piston filling (4) and/or a piston washer (5) and/or a stationary filling (6), at the same time as the engine is provided with an especially strong throttling created in the engine's exhaust side, i.e. in its exhaust port (9) and/or in a possible exhaust duct (10) and/or in the muffler (2).

Abstract: A twin-piston engine (1), i.e., a crankcase scavenged two-stroke internal combustion engine comprising two pistons (2,3) travelling in essentially the same direction, and wherein one (4) of the cylinder bores, the exhaust bore (4), contains all exhaust ports (6), and the other cylinder bore (5), the scavenging cylinder bore, contains a number of scavenging ports (7,8,9).

Abstract: Emission gasses from an engine exhaust pipe are collected through an inlet of a dilution tunnel which is an elongated, hollow tube. The inlet is spaced from the exhaust pipe to also admit surrounding air. Ambient air and emissions are mixed in the tunnel by a screen in the tunnel. A probe in the tunnel diverts a portion of the mixture to gas analyzers. Prior to analysis the mixture may be condensed, filtered or otherwise processed. The analysis determines a CO/CO.sub.2 ratio which is used to determine the air/fuel ratio in the engine based on characteristics of the fuel. The air/fuel mixture of the engine is then adjusted to achieve desired performance.

Abstract: Emission gasses from an engine exhaust pipe are collected through an inlet of a dilution tunnel which is an elongated, hollow tube. The inlet is spaced from the exhaust pipe to also admit surrounding air. The air and emissions are mixed in the tunnel by a screen in the tunnel. A probe in the tunnel diverts a portion of the mixture to gas analyzers. Prior to analysis the mixture may be condensed, filtered or otherwise processed.