The Fi2000 works on a simple premise. Most bike modifications -- pipes, filters, ignition advancers -- will make an already lean-running model even leaner. (Lean means that the fuel/air mixture has less fuel and more air than desirable; a rich mixture has too much fuel. Up to a point, a lean mixture will make a bike lose power and run hot, while a rich mixture will start to hurt power only when the imbalance becomes excessive. The theoretically ideal ratio is approximately 14 parts air to one part fuel, though maximum power is obtained near 12:1.) Back to the Fi2000: Assuming all you need to do is add fuel -- making the mixture richer to compensate for the modifications -- the design of a device to accomplish this becomes radically simpler.