One feature of the invention resides broadly in a crankcase scavenged internal combustion engine (1) mainly intended for a handheld working tool, such as a chain saw, with an engine body (2) composed of at least one crankcase body (3, 4) and a cylinder body (5), which are joined together, and the engine is provided with so called elongated scavenging ducts (6,7,6???,7???), which over some part of