Annually or every 20,000 km.
Carburetor engines
1. Release the spring clips, then loosen the center nut and remove the cover.
2. Remove the filter element and wipe the air filter housing and cover clean.
3. Install the new filter element, then install the cover in the reverse order of removal.
Engines with central fuel injection system
1. Loosen the clamp on the intake air duct and disconnect the air duct.
2. Release the air cleaner cover retaining clips.
3. Unscrew the lid upwards,..
...remove it and take out the element, noting which way it should be screwed in.
4. Use a clean cloth to wipe the inside of the filter housing, then install the new element. If the element has a TOP mark, be sure to install it with this side facing up.
5. Replace the lid and close the clamps.
6. Connect the air duct and tighten the clamp screw.