Yamaha - Carburetor Assembly Fuel System Component YA2-63623-85-00. Overview. When a Yamaha starts idling rough or losing that clean throttle response, the carburetor is usually where I look first. I've swapped plenty of worn units that were causing hesitation and fuel issues, and the difference is immediate when everything's dialed back in. The Yamaha Carburetor Assembly YA2-63623-85-00 restores proper fuel-air balance so the engine runs the way it should. It's a solid fix when performance star