Subject of this paper is analysis of load on piston mechanism journal bearings between different types of motorcycle engine build concepts – Boxer-2 and V-2 enginеs. Firstly, components of piston mechanism are modeled in software for 3D modeling. Result of this are geometrical and mass properties of components. In order to get value of driving force (gas force), model is made using software for one dimensional gas analysis. By knowing these input values, a multi-body dynamic model of piston mechanism is made using software for MBD and its output results in terms of journal bearing forces are aquired. These results are than compared and evaluated. Posibilities for further research and improvement are also stated.