If they appear damaged or deteriorated, replace them.

Balancer Adjustment
Torque LimiterSpark Plug Condition Inspection
Remove the spark plugs (see Spark Plug Replacement in
the Periodic Maintenance chapter).
Visually inspect the spark plugs.
If the spark plug center electrode [A] and/or side electrode
[B] are corroded or damaged, or if the insulator [C]
is cracked, replace the plug.
If the spark plug is ...
Cleaning Vehicle before Disassembly
Clean the vehicle thoroughly before disassembly. Dirt or
other foreign materials entering into sealed areas during vehicle
disassembly can cause excessive wear and decrease
performance of the vehicle.
Arrangement and Cleaning of Removed Parts
Disassembled parts are easy to confuse. Arrange ...
Release Shaft Installation
Apply grease to the oil seal lips on the upper ridge of the
clutch cover.
Apply engine oil to the needle bearings in the hole of the
clutch cover.
Applymolybdenum disulfide grease to the pusher-holding
portion [A] on the release shaft.
Install the washer [B] and spring [C].
...