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 ...
Rear Wheel Installation
Apply high-temperature grease to the grease seal lips.
Fit the collars on the both sides of the hub.
Left Side Collar [A]
Right Side Collar [B] (with Flange)
Engage the drive chain with the rear sprocket.
Install the caliper bracket [A] onto the stopper [B] of the
swingarm.
...
Intake Air Pressure Sensor #1 Installation
NOTE
The intake air pressure sensor #1 is the same part as
the intake air pressure sensor #2.
Installation is basically the reverse of removal.
Position the intake air pressure sensor #1 [A] between the
projections [B] on the rubber damper.
Install the rubber damper [A] on the bracket ...