No, it is not feasible to directly install a Yamaha R15 V3 engine onto a Yamaha R15 V2. The R15 V3 engine is designed specifically for the R15 V3 model, and there are significant differences between the two generations in terms of engine architecture, specifications, and compatibility.
The R15 V3 engine features a larger displacement, different internal components, and updated technology compared to the R15 V2 engine. These differences extend beyond just the engine itself and include the supporting systems, such as the fuel injection system, electronics, and wiring harness, which are designed to work harmoniously with the specific generation of the motorcycle.
Attempting to install a different generation's engine onto a motorcycle that it was not designed for would require extensive modifications, including alterations to the frame, mounting points, and various supporting systems. Such modifications are not only complex but also carry significant risks in terms of safety, performance, and reliability.
If you are looking to upgrade the engine of your Yamaha R15 V2, it is advisable to explore options that are compatible and specifically designed for that model. Consulting with an authorized Yamaha dealer or a reputable motorcycle mechanic would be the best course of action to explore suitable engine upgrades or modifications for your specific motorcycle.