The crankshaft is the component which transmits dynamic loads from cylinder pressure and inertial loads in engine operating conditions. Because of its crucial importance in functioning of engine and requisite to sustain high dynamic and torsional loading, crankshaft fatigue life is desired to be higher than the predicted engine operating life.Performance of the crank train in diesel engine applications largely depends on the components of its mass elastic system. Flywheel is one such component whose design affects the life of crankshaft.In the present study, the crank train comprising of torsional vibration damper, crankshaft and flywheel along with clutch cover is considered for analysis. Crankshaft dynamic simulation is performed with multi body dynamics technique, fatigue safety factors of crankshaft are calculated with dynamic loads under engine operating conditions. The effect of Single Mass Flywheel (SMF) mass and its Center of Gravity (CG) distance from the center of rear main journal bearing, on the crankshaft factor of safety is analyzed. In addition, proportional variation of important parameters like speed irregularity, torsional vibration amplitude and load on main bearing are also investigated.