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 ...
Wheel Rotation Sensor Air Gap Inspection
Raise the front/rear wheel off the ground (see Front/Rear
Wheel Removal in the Wheels/Tires chapter).
Measure the air gap between the sensor and sensor rotor
at several points by turning the wheel slowly.
Thickness Gauge [A]
Wheel Rotation Sensor Air Gap
Standard:
Front 0.4 1.6 mm ...
Wheel/Tire Damage Inspection
Remove any imbedded stones [A] or other foreign particles
[B] from tread.
Visually inspect the tire for cracks and cuts, and replace
the tire if necessary. Swelling or high spots indicate internal
damage, requiring tire replacement.
Visually inspect the wheel for cracks, cuts and dents ...