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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblySwingarm Installation
Visually inspect the chain guide [A].
Replace the chain guide if it shows any signs of abnormal
wear or damage.
Apply a non-permanent locking agent to the threads of
the chain guide bolt [B].
Apply plenty of grease to the lip of the oil seals [A].
Be sure to install the oil seals ...
Stop Watch
The stop watch can be used in closed
course competition.
The stop watch is operated as follows:
Push the upper button to display the
stop watch.
To start the stop watch, push the
“START/STOP” switch on the right
handlebar switch to the left.
A. “START/STOP” Switch
...
External Shift Mechanism Removal
Remove:
Shift Lever (see Shift Pedal Removal)
Oil Pump Drive Gear (see Oil Pump Drive Gear Removal/
Installation in the Engine Lubrication System
chapter)
Circlip [A]
Washer [B]
Special Tool - Outside Circlip Pliers: 57001-144
Remove:
Shift Shaft Assembly [A]
Washer [B] ...