Why, you ask?
Well... number one, it's easy, cheap and quick. Number two, the factory fill of gear oil is sure to pick up some swarf and metallic debris from brand new gears mashing together and I thought it prudent to get that dirty crap out of there. Thirdly, I enjoy working on my motorcycles and I don't believe in such a thing as "too much maintenance"
1. Remove the final drive cowl. 3 little Allen screws hold it in place.