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A detailed knowledge of the scavenging process becomes necessary during the development process, when the performance and in particular the emission output of two-stroke engines needs to be qualified and evaluated. This paper presents an experimental approach to describe the composition of the flow at the exhaust port by means of flow visualization and to quantify the relative changes of the scavenging losses imposed by design changes. The experimental set-up has been described in previous SAE papers and has been expanded by a transparent exhaust port, which gives optical access to the flow through the exhaust port. The gases in the cylinder are represented by differently colored water-based fluids. Typically, the burnt gas is clear and the fresh charge is colored to visualize its progress during the scavenging cycle and its distribution inside the cylinder.