Honda WT40 Owner's Manual page 36

SERVICING YOUR PUMP
3. Separate the foam and paper air filter elements. Check both filter elements,
and replace them if they are damaged. Always replace the paper air filter
element every year or 300 hours. Clean the air filter elements if they are to be
reused.
Paper air filter element: Tap the filter element several times on a hard surface
to remove dirt, or blow compressed air [not exceeding 30 psi (270 kPa,
2
2.1 kg/cm )] through the filter element from the inside out. Never try to brush
off dirt; brushing will force dirt into the fibers.
Foam air filter element: Wash in warm, soapy water, then rinse thoroughly, or
wash in non-flammable solvent. Allow the filter element to dry thoroughly.
Dip the filter element in clean engine oil, and then squeeze out all excess oil.
The engine will smoke when started if too much oil is left in the filter element.
Clean
4. Wipe dirt from the air cleaner base and cover (and silencer if applicable),
using a moist rag.
5. Place the foam air filter element over the paper air filter element, and install
the assembled air filter. Be sure the gasket is in place beneath the filter.
Tighten the wing nut securely.
6. Reinstall the air cleaner cover, and tighten the wing nut securely.
34
Squeeze and dry
Do not twist.
Dip in oil Squeeze
Do not twist.