Drilling small holes into your Yamaha YBR engine is not a recommended or advisable way to make it louder. Modifying the engine in such a manner can have negative consequences for the performance, reliability, and overall functionality of the engine.
The noise produced by a motorcycle engine is a result of various factors, including the exhaust system, intake system, and engine design. Modifying these components in a controlled and engineered manner, such as replacing the exhaust system with an aftermarket one designed for improved sound, may result in a louder exhaust note.
It can disrupt the proper functioning of the engine by altering the airflow, fuel mixture, and internal pressure. This can lead to decreased performance, increased fuel consumption, loss of power, and potential damage to engine components.
If you're interested in altering the sound of your Yamaha YBR, it is recommended to explore aftermarket exhaust options specifically designed for your motorcycle model. These exhaust systems are engineered to enhance the sound while maintaining proper performance and reliability.
It's important to note that local laws and regulations regarding noise emissions may apply, so ensure any modifications you make comply with the legal requirements in your area.