Yamaha BIG BEAR YFM400FPP Owner's Manual page 300

8. Reinstall the element to the element guide.
9. Reinstall the element assembly and parts re-
moved for access.
NOTE:
The air filter element should be cleaned every 20 ~
40 hours. It should be cleaned and lubricated more
often if the machine is operated in extremely dusty
areas. Each time filter element maintenance is
performed, check the air inlet to the filter case for
obstructions. Check the air cleaner rubber joint to
the carburetor and manifold fittings for an air-tight
seal. Tighten all fittings securely to avoid the pos-
sibility of unfiltered air entering the engine.
CAUTION:
Never operate the engine with the air filter ele-
ment removed. This will allow unfiltered air to
enter, causing rapid engine wear and possible
engine damage. Additionally, operation with-
out the filter element will affect carburetor jet-
ting with subsequent poor performance and
possible engine overheating.
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