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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyClutch Lever Installation
Install the clutch lever so that the mating surface [A] of the
clutch lever clamp is aligned with the punch mark [B] of
the handlebar.
Tighten the upper clamp bolt first, and then the lower
clamp bolt.
Torque - Clutch Lever Clamp Bolts: 7.8 N·m (0.80 kgf·m, 69
in·lb)
There will be ...
Piston Ring Thickness Inspection
Measure the piston ring thickness.
Use the micrometer to measure at several points around
the ring.
Piston Ring Thickness
Standard:
Top [A] 0.77 0.79 mm (0.0303
0.0311 in.)
Second [B] 0.78 0.79 mm
(0.0307 0.0311 in.)
Service Limit:
Top 0.70 mm (0.0276 in.)
Second 0.71 mm (0.0280 ...
Fuel Injector Fuel Line Inspection
Remove:
Fuel Tank (see Fuel Tank Removal)
Air Cleaner Housing (see Air Cleaner Housing Removal)
Disconnect:
Primary and Secondary Fuel Hoses (see Fuel Hose Replacement
in the Periodic Maintenance chapter)
Do not remove the nozzle assy from the air cleaner housing.
Be sure to pla ...