When increasing the engine displacement of your Yamaha TTR 125cc to a 150cc, it's generally recommended to use a carburetor specifically designed for the increased displacement. Here are a few reasons why:
Proper Fuel-Air Mixture: A carburetor designed for a 150cc engine will have jets and other internal components calibrated to deliver the appropriate fuel-air mixture for that engine size. This helps ensure optimal performance and fuel efficiency.
Improved Performance: Using a carburetor specifically designed for a 150cc engine can potentially result in better throttle response, power delivery, and overall performance. The carburetor's design will be better suited to meet the increased airflow demands of a larger engine.
Simplified Tuning: Using a carburetor designed for a 150cc engine can simplify the tuning process. While it's possible to jet a 125cc carburetor to work with a 150cc engine, it can be a more involved and time-consuming process, requiring precise adjustments and potential trial and error.
Compatibility and Reliability: Using a carburetor designed for a 150cc engine ensures compatibility with the larger engine components and reduces the risk of issues arising from mismatched parts. It can contribute to the overall reliability and longevity of your modified engine.
To ensure the best results and avoid potential complications, it's recommended to consult with an experienced mechanic or tuner who specializes in engine modifications. They can provide specific guidance based on your Yamaha TTR model and the available options for a 150cc carburetor or jetting a 125cc carburetor. They can also help you make an informed decision based on the specific characteristics of your engine and desired performance goals.