I checked my air filter have a couple of questions. First, How can I tell If I need to replace it. It appears a little dirty but not too bad. Second, What is that little plastic box sitting under the filter. It appeared to be some type of filter or something. It was kinda oily.

 

A little oil there is normal, don't worry, it's connected to the engine crankcase and some oil mist make it's way there, depending of your riding conditions, replace the filter after 10000-15000 miles is a good average.

 

werd