In this study, by preparing a dynamic model for the system consisting of piston, piston rod, crankshaft and block of a single cylinder four stroke diesel engine, the speed fluctuations of the crankshaft and translational vibrations of the engine block were examined. The dynamic model has four degrees of freedom as; the angular motion of the crankshaft, the angular motion of the engine block around the crankshaft center, and the translational vibrations of the engine block in the vertical and horizontal directions. In the analysis, the pressure profiles obtained from a single cylinder four stroke diesel engine at four different engine loads were used. The oscillation of crankshaft angular velocity was found to be increasing with the engine load. The angular vibrations of the engine block around the crankshaft center was found to be arising from the gas forces, the translational vibrations in the vertical and horizontal directions were found to be arising from the inertia of piston and unbalance of crankshaft. It was found that the counterweight used for minimizing the vertical vibration generates a horizontal vibration besides reducing vertical vibration. Therefore, reduction of its amplitude into the half was found to be more appropriate, instead of reducing to zero. From the mount force datum, which is dependent on frequency, the optimum spring and damping constants of the mounts were found as 100 kN/m and 1000 Ns/m, respectively.