First, it helps to understand the problem that motor tuning solves. The best analogy for motor tuning is cruise control on a car. When you set your cruise control to 55 mph, the car has to adjust the amount of fuel going to the engine to keep moving at that speed. If you are going up hill, the car lags for a second and then more gas rushes into the engine and the car speeds up to get back to the desired speed. Similarly, the car needs to regulate the amount of gas when going down a hill.