For the 2001 model year Honda released an upgraded version of the popular Honda CBR600 F4i with intentions of becoming more competitive in the middleweight sport bike class. The 370 pound F4i is a modified F4 with numerous engine, chassis and CBR600 F4i bodywork changes.
The single largest change, other than the styling, is the addition of high-pressure (50 psi) programmed fuel injection - thus the model designation "F4i". Fuel injection allows for more precise fuel metering and delivery over a wider rpm range, while providing better throttle response and decreasing emissions. The injectors reside one per cylinder and work with 38 mm throttle bodies. Each injector has four nozzles, and together the injectors add up to five horsepower over the F4. The wheelbase is five millimeters shorter than its predecessor, with a 5.9-percent increase in overall rigidity. CBR600 F4i Fairings