Portable manually operated tool with forward-scavenged two-stroke i.c. engine

A tool such as a chain saw or brush cutter has a reciprocating-piston two-stroke engine 1. On both sides of a cylinder centre plane are positioned transfer passages 12, 15 which connect the crankcase 4 to the combustion chamber 3. A first end of a transfer passage 12, 15 is connected via an inlet window 13, 16 to the combustion chamber, while the second end of the transfer passage is open to the crankcase 4. The transfer passages 15 are located nearer to the exhaust port 10 and are connected to an air duct 20 which supplies fuel-free air via a filter 19 and a control element 21 forward of the air/fuel mixture being inducted to reduce fuel loss during scavenging. The air duct 20 is formed by a duct section 29 in a housing wall 23 of the tool, the wall being positioned between a carburettor 8 and the cylinder 2 of the internal combustion engine 1.