If they appear damaged or deteriorated, replace them.

Balancer Adjustment
Torque LimiterValve Guide Removal
Remove:
Valve (see Valve Removal)
Oil Seal
Spring Seat
Heat the area around the valve guide to 120
150°C (248
302°F), and hammer lightly on
the valve guide arbor [A]
to remove the guide from the top of the head.
NOTICE
Do not heat the cylinder head with a torch. This ...
Crankshaft Sensor Installation
Apply a non-permanent locking agent to the crankshaft
sensor bolts [A].
Tighten:
Torque - Crankshaft Sensor Bolts: 5.9 N·m (0.60 kgf·m, 52
in·lb)
Using a high flash-point solvent, clean off any oil or dirt
that may be on the silicone sealant coating area. Dry
them with a clean cl ...
Check 2-1: Speedometer Inspection
Using the suitable stand, raise the rear wheel off the
ground.
Rotate the rear wheel by hand or start the engine.
Check that the display changes speedometer.
If the display function does not work, check the following
parts.
Rear Wheel Rotation Sensor (see Wheel Rotation Sensor
Inspe ...