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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyAmplifier Input Voltage Inspection
NOTE
Be sure the battery is fully charged.
Turn the ignition switch to OFF.
Remove the upper fairing (see Upper Fairing Removal in
the Frame chapter).
Do not disconnect the connectors.
Connect a digital meter to the amplifier connector [A] with
needle adapter set.
Special To ...
Fuel Tank Installation
Note the above WARNING (see Fuel Tank Removal).
Run the hoses correctly (see Cable, Wire, and Hose Routing
section in the Appendix chapter).
Check that the dampers [A] are in place on the fuel tank.
If the dampers are damaged or deteriorated, replace
them.
If the fuel tank brack ...
Seat Cutter Operation Care
1. This valve seat cutter is developed to grind the valve for
repair. Therefore the cutter must not be used for other
purposes than seat repair.
2. Do not drop or shock the valve seat cutter, or the diamond
particles may fall off.
3. Do not fail to apply engine oil to the valve seat cutter
...