This paper deals with designing and development methodology of Automatic Electric Start (AES) system for power tiller which has horizontal diesel engine as prime mover. Designing of AES system constitutes of designing of Starter Motor, Starter Motor Bracket, Flywheel Ring Gear, Battery, Electrical Circuit, Fan Alternator and then development these components as integrated system prototype. Unlikely tractor market, AES system are not so common in Indian power tiller market therefore, unprecedented design approach towards design of AES system on power tiller engine has been presented in this paper. An engine without AES system requires of huge amount of engine starting effort by farmer whereby farmers fatigue levels are always on higher side. AES system on power tiller has made 0 N force requirement to start engine which was approximately 92 N earlier. Design of AES system depends on analysis engine cranking torque, which is a complex process and involves calculation of moments, such as gas torque, friction torque, and inertia torque of engine. With the help of theoretical relations and using GT POWER tool engine cranking torque value has been calculated. Presented engine in this paper requires 70 Nm of cranking torque. Firstly starter motor power is calculated based on cranking torque. Secondly, based on predicted failure modes and causes, RPN values are generated and prudential approach is overhauled in this paper towards the design of ring gear parameters (Profile Coeff, Tip Dia, Width, Depth of tooth etc.) , starter bracket and battery selection. Finally, ANSYS is used to evaluate stress concentrations on designed components through simulation of the actual loadings conditions. A testing approach of AES system is also discussed for validation.