Replace it if necessary.

Inner Tube Inspection
Spring Tension InspectionSpark 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 ...
Nozzle Assy Assembly
Before assembling, blow away dirt or dust from the delivery
pipes [A] by applying compressed air [B].
Replace the O-rings [A] of the joint pipe [B] with new ones.
Apply engine oil to the new O-rings, and insert it to the
delivery pipes [C]
Insert the joint pipe so that the step ...
Mud Guard Installation
Installation is the reverse of removal. Note the following.
Run the hose and lead correctly (see Cable, Wire, and
Hose Routing section in the Appendix chapter).
Check the brake line.
Apply a non-permanent locking agent to the threads of
the mud guard mounting bolts [A, B], and tighten them ...