If the surface is corroded or if the blades are damaged, replace the impeller

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyAntenna Resistance Inspection
Turn the ignition switch to OFF.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter).
Disconnect the antenna lead connector [A].
Measure the antenna resistance.
Antenna Resistance
Connections: BK lead ←→ BK/W lead
Standard: Ab ...
Meter Unit Removal/Installation
Remove the upper fairing assembly (see Upper Fairing
Assembly Removal in the Frame chapter)
Remove the bolt [A] (other than US, CA and CALmodels).
Slide back the dust cover and disconnect the meter unit
connector [B].
Remove:
Bolts [A]
Nut [B] (other than US, CA and CAL mode ...
Subthrottle Sensor Input Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the air cleaner housing (see Air Cleaner Housing
Removal in the Fuel System (DFI) chapter)
Disconnect the subthrottle sensor connector and connect
the harness adapter [A] between these connectors.
Spec ...