The diesel power train (engine and transmission) is the most significant mass contributor in a three- wheeled vehicle. High idling vibrations from the engine get transmitted to the structure and the body panels through the engine mounts. Isolation of these vibrations by proper design of rubber mounts is the most effective engineering approach to improve ride quality of vehicle. In the present study, a mathematical model of the powertrain and mount system is developed; with the engine and transmission being assumed to behave as a rigid body (6 degrees-of-freedom) and the compliance comes from the mounts. As a first step, the modes and natural frequencies are obtained. Following this the response to unbalanced inertial forces for an excitation frequency range of 20-60 Hz (1200-3600 rpm) has been obtained. The model is validated by comparing its results with results of previous published research work. Also, motoring experiments are conducted on a baseline configuration to obtain the vibration response at mounts and mode shapes through ODS (Operational Deflection Shape) for validating the math model. A detailed parametric study is conducted and a new combination of mount system design variables were arrived as proposed solution which in comparison with baseline configuration showed that the vibration response reduces by 40% at idling and 60% in the engine operating range. Experiments conducted on the improved design show similar improvement. Thus, using this validated analytical math model, a closer-to-optimal design can be obtained with minimal dependency on iterative experimental methods which are costlier and time consuming.