The air filter and PCV filter are to be changed by new ones at certain time intervals and a comprehensive preventative maintenance program would require the two filters to be checked in between. The air filter is found in the air cleaner housing on the engine top, and is changed by unscrewing the wing nut on the top of the air cleaner housing, unclips the clips and the top plate is raised off. The top plate should not be replaced when it is off but caution must be taken not to drop anything in the carburetor. The air filter element may be then removed out of the housing and the interior of the air cleaner housing wiped out with a clean rag. The air cleaner housing should be put back then the new filter should be inserted as making sure that it fits well at the bottom. The PCV filter is housed as well in the air cleaner located inside the air cleaner housing; once the top plate and air filter are removed, the PCV filter is found on the side of the housing. One can pry the filter up with a screwdriver and then remove it out of the housing. Lastly, a new PVC filter and air filter are added and the top plate fitted making sure the arrow is in the same line with the arrow of the air intake.