Changing the Main Gear on a Mad Hawk 300/Walkera CB180

This simple procedure baffles a lot of beginners, but it really isn't that hard. Determining the right spacing between the motor pinion and main gear is a question I come across in the forums, but I can never seem to find a picture of how to do it or what it really means. Well, here is visual documentation. As primitive as it might be, it's a visual.