[meganuke]

How often should you change the air filter? I haven't received an owners manual, so I'm relying on the collective wisdom of the forum.

[Arizoni]

IMO, it depends on how dusty the area the bike is ridden in is but the owners manual for my G5 says to clean the filter at the 300, 2000, 3750 and 6000 mile scheduled maintenance intervals.
It says the filter should be replaced at the 7500 mile service.

If your C5 is like my G5, the air comes into the filter from the inside and passes thru the filter media to end up in the filter compartment where the inlet to the throttle body connects.
Because of this if you blow out the dirt on your filter you will want to blow the compressed air against the outside of the filter element.

By the way, those mileages I mentioned are the recommended oil & oil filter change intervals (although I change mine more often).