I just changed my oil on my wr400f!!! I cleaned the oil strainer and oil filter. It was not easy at all! It took me about 2 hours to change it! You have to take off so many parts to change the oil! It's crazy! It's worth it though! I've heard of people that never changed their oil until the dirtbike didn't run well! If you have a dirtbike you have to maintain it bottom line!