If any one of the parts is damaged, replace the mechanical seal as a unit.
Rubber Seal [A] Mechanical Seal [B]

Water Pump Housing Assembly
RadiatorClutch
Clutch Operation Inspection
Pull the clutch lever just enough to take up the free play
[A].
Measure the gap between the lever and the lever holder.
If the gap is too wide, the clutch may not release fully. If
the gap is too narrow, the clutch may not engage fully. In
either case, adjust ...
Fuel Pressure Inspection
NOTE
Be sure the battery is fully charged.
Remove:
Fuel Tank Covers (see Fuel Tank Removal)
Fuel Tank Bolts (see Fuel Tank Removal)
Primary Fuel Hose (see Fuel Hose Replacement in the
Periodic Maintenance chapter)
Be sure to place a piece of cloth around the fuel outlet
pipe of the ...
Piston Wear Inspection
Measure the outside diameter [A] of each piston 5 mm
(0.20 in.) [B] up from the bottom of the piston at a right
angle to the direction of the piston pin.
If the measurement is under service limit, replace the piston.
Piston Diameter
Standard: 75.959 75.974 mm
(2.9905 2.9911 in.)
...