Down-sizing of motorcycle ECU becomes essential requirement because of vehicle load capacity. Furthermore, cost-down is drastically required and components selected in ECU, such as built-in RAM capacity of CPU, are reduced maximally because motorcycle is in low-priced range mostly. The different things of ECU from four-wheeled vehicle affect vehicle calibration in development. It is ideal for using such ECU which has suitable size for vehicle and the minimum built-in RAM capacity of CPU to implement vehicle control, instead of using dedicated development ECU which is in large size and needs additional investment in vehicle calibration for motorcycles. This research has explored techniques for vehicle calibration based on mass-production ECU in order to find particular solution for motorcycles.Vehicle calibration is sequential procedure which adjusts control data of ECU by using PC application software to measure and analyze bench or vehicle test information repeatedly aiming to achieve target performance of vehicle. A typical technique utilized for dedicated development ECU is to reflect all control data deposited in ROM to RAM, and edit RAM data directly. As an alternative for motorcycle, same calculation logic as ECU control software is introduced into PC application software. ECU software is structured available to shift adjustment target of control logic, and this shift is executed according to command from PC application software. Depending upon these countermeasures, adjustment target of control logic selection on PC application software can realize corresponding control logic adjustment mode shift on ECU, then, PC application software calculates calibration data for target control logic adjustment, and send the result to ECU for implementation. Accomplishment of such successive procedure makes vehicle calibration on mass-production ECU feasible.Two-way algorithm for ECU software and PC application software have been established, the effectiveness and validation have been proved through mass-production development practice.