There is a new company offering a really trick fuel injection conversion for carbureted Ninjas. Originally sold for retrofits of the millions of 50-150cc scooters in India and Asia, the company realized it was easily possible for them to double up the hardware to adapt the kit to the small two cylinder Ninja. They have been very responsive to suggestions and have been continually pushing the design forward over the last year to the point where they were able to add enough processing power to incorporate real time closed loop trim via two independent channels with wide band O2 sensors. I don't think there is any other vehicle on the road that can do that. Trimmed to your own maps that you fine tune from your lap top after logging the wide band sensors with some riding time. You can set 13.4 : 1 at full throttle for maximum power and run 16 : 1 lean burns at light throttle for the best fuel efficiency. For $600.
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Group Buy: EFI (Fuel Injection) Conversion Kit - ninjette.org