The important internal dynamic interactions which ultimately determine the performance of a two-stroke internal combustion engine are identified and then modeled using the bond graph modeling technique. Each of the important dynamic characteristics are developed independently, presenting both the bond graph and mathematical formulation of each of the assumed subsystems. These subsystems are assembled into the final overall system bond graph and governing state space equations are derived. The result of this development is a reasonably straightforward procedure for assembling virtually any size two-stroke ICE with virtually any internal geometry into a cogent, simulatable mathematical formulation.The procedure outlined above is demonstrated for the Yamaha 360 MX motorcycle engine. In addition to presenting results for various internal dynamic interactions (pressure, flow, temperature, etc.), the model is shown to yield excellent predictions for power and torque as a function of RPM.