The heat transfer from cylinder to air of a two-stroke internal combustion finned engine has been simulated. For this purpose, a 2D model of the block and head has been done. Starting from the geometry of a real engine, annular cylindrical and spherical symmetric walls to fins has been used to obtain an equivalent simplified geometry, where the heat transfer rate is the same as that in the real engine. The cylinder body, cylinder head (both provided with fins), and piston have been numerically analyzed and optimized in order to minimize engine dimensions. The maximum temperature admissible at the hottest point of the engine has been adopted as the limiting condition. An engine temperature map has been presented as additional information. Cyclically variable inner cylinder conditions (thermodynamic, thermal, and chemical) proceed from a previous work; convective and radiative inner boundary conditions and convective external conditions have also been taken into account in this work. A network simulation model has been used as the numerical tool in the analysis presented.