Replace the gasket if it is damaged.
If they are clogged, remove the tank and drain it, and then blow the breather free with compressed air.

NOTICE
Do not apply compressed air to the air vent holes [D] in the tank cap. This could cause damage and clogging of the labyrinth in the cap.
Fuel Tank Installation
Fuel Tank CleaningEngine Vacuum Synchronization Inspection
NOTE
These procedures are explained on the assumption that
the intake and exhaust systems of the engine are in
good condition.
Situate the motorcycle so that it is vertical.
Remove:
Fuel Tank (see Fuel Tank Removal in the Fuel System
(DFI) chapter)
Air Cleaner Housing (see Air Cleaner ...
Intake Air Temperature Sensor Output Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the fuel tank (see Fuel Tank Removal in the Fuel
System (DFI) chapter).
Disconnect the intake air temperature sensor connector
and connect the measuring adapter [A] between these
connectors as shown in ...
Shift Pedal Removal
Remove:
Shift Lever Bolt [A]
Front Footpeg Bracket Bolts [B]
If the tie-rod [C] is to be removed from the shift pedal and
the shift lever, loosen the tie-rod locknuts [D].
The front tie-rod locknut is left-hand thread.
Remove:
Shift Pedal Mounting Bolt [A]
...