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

Water Pump Impeller Disassembly/Assembly
Water Pump Housing DisassemblyCylinder (Upper Crankcase) Wear Inspection
Split the crankcase (see Crankcase Splitting).
Remove the pistons (see Piston Removal).
Assemble the cylinder (upper crankcase) [A], the cylinder
head [B] and the cylinder head gasket [C].
Tighten the cylinder head bolts (see Cylinder Head Installation
in the Engine Top End chapter).
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Oil Pressure Measurement
Remove:
Right Lower Fairing (see Lower Fairing Removal in the
Frame chapter)
Oil Passage Plug [A]
Attach the adapter [A] and gauge [B] to the plug hole.
Special Tools - Oil Pressure Gauge, 10 kgf/cm²: 57001-164
Oil Pressure Gauge Adapter, PT3/8: 57001
-1233
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Oxygen Sensor Removal (Equipped Models)
Remove:
Fuel Tank (see Fuel Tank Removal in the Fuel System
(DFI) chapter)
Right Lower Fairing (see Lower Fairing Removal in the
Frame chapter)
Disconnect the oxygen sensor lead connector [A].
NOTICE
Do not pull strongly, twist, or bend the oxygen sensor
lead. This may cause the wi ...