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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyCheck 3-3: High Beam Indicator Light (LED) Inspection
Connect the leads in the same circuit as Check 3-2.
Connect the terminal [7] to the battery (+) terminal.
Check that the high beam indicator light (LED) [A] goes
on.
If the indicator light does not go on, replace the meter unit.
...
Brake Fluid Level Inspection
Check that the brake fluid level in the front brake reservoir
[A] is above the lower level line [B].
NOTE
Hold the reservoir horizontal by turning the handlebar
when checking brake fluid level.
If the fluid level is lower than the lower level line, fill the
reservoir to the upper lev ...
Battery Removal
Turn off the ignition switch.
Remove the front seat (see Front Seat Removal in the
Frame chapter).
Slide the red cap [A].
Disconnect the negative (–) cable [B] and then positive
(+) cable [C].
NOTICE
Be sure to disconnect the negative (–) cable first.
Remove the band [D] ...