Yamaha - Carburetor Lower Assembly Fuel Delivery Component 6K5-14303-03-00. Overview. The Yamaha Carburetor Lower Assembly 6K5-14303-03-00 is one of those parts that can quietly throw everything off when it starts to wear out. If your engine's been idling rough or not responding cleanly on throttle, this lower section of the carb is often where the issue sits. It handles fuel flow and sealing inside the carb body, so everything has to stay tight and clean. Swapping it out is a solid move when you want your motor running smooth and predictable again.. Key Features. • Consistent Fuel Flow Control - Regulates fuel movement through the carburetor for steady engine performance.. • OEM Fit Precision - Matches Yamaha carburetor design for proper alignment and sealing.. • Improved Idle Stability - Helps eliminate rough idle and uneven engine behavior.. • Durable Marine Construction - Built to handle fuel exposure, vibration, and harsh conditions.. Compatibility. Compatible with select Yamaha o