High-volume vertical check valve located in the QS3 for precise, consistent fuel metering. Tunable leak jet maximizes volume of fuel and duration of fuel spray for all conditions. Integrated Hot Start Assist eliminates problem 4-stroke hot start procedure. The most effective way to add performance to a Keihin FCR carburetor. Patented design stops bogging and improves throttle response. Investment cast and finished to precise tolerances. Improved low-end performance. Simple bolt-on installation. 25% more fuel capacity. For all Keihin FCR-Equipped MX, Off Road and ATV models..