While preserving the advantages of the CR Special, the FCR carburetor has been greatly improved by using bearing rollers at the throttle valves, leading to significantly lighter and more comfortable accelerator operation. Inheriting the traditional CR high-efficiency venturi shape, the dead space in the venturi was eliminated to reduce vortex current losses and enable power-up at especially flow speeds. Additionally, the FCR has a throttle valve, balance valve assembly that ensures high airtightness as well as stable idling and is equipped with a diaphragm type accelerating pump, short venturi tunnel, so that the carburetor can have a larger diameter in response to the high-output engines while already exerting great power when accelerating from low to medium speeds and providing powerful acceleration.