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Improvements in the engine performance, efficiency, scavenging, and emission characteristics of a modified two-stroke-cycle engine with the poppet valves and gaseous-fuel direct-injection system are described. In previous papers, SAE 901664 [1]* and 920180 [2], in which the scavenging characteristics were mainly investigated, the modified two-stroke-cycle engine was based on a production four-stroke-cycle engine. The base engine intake valve was used as scavenging valve, with a shroud installed for preventing the short-circuiting charge loss. As Shown in the previous results, considerable improvement of the scavenging efficiency was obtained. While a gasoline fuel carburetion system was used in the earlier engine [1], [2], the present engine used a propane gas direct-injection system, with the purposes of further decreasing fuel short-circuiting loss and also improving combustion preparation characteristics in terms of fuel atomization, vaporization and mixing with air.