In at least some embodiments, the present invention relates to an air cleaner having a housing portion, and a low profile rain cover having an opening on an underside of the cover to allow unfiltered air to enter into the air cleaner. Also, in at least some embodiments, the present invention relates to an air cleaner including a housing and an additional component by which the air cleaner is capable of being directly coupled to a carburetor inlet. In some such embodiments, one or more protrusions can be provided within a channel formed by the housing/additional component to influence air flow. Further, in at least some embodiments, the present invention relates to an air cleaner having a shaped wall formed on a housing portion, where the shaped wall includes both an interior surface and an exterior surface by which air flowing within the air cleaner is imparted with helical motion.