Honda PCX125 - Owner's Manual > Engine


Throttle Inspection

1. Check that the throttle assembly is positioned properly and the securing bolts are tight.

2. Check for smooth rotation of the throttle from fully open to fully closed in all steering positions. If there is a problem, see your Honda dealer.

Spark Plug

Spark Plug Recommendation

Spark Plug

Use only the recommended type of spark plug in the recommended heat range.

Using spark plugs with an improper heat range can cause engine damage.

Spark Plug Replacement

1. Remove the screw (1) and the plug maintenance lid (2).



  1. screw
  2. plug maintenance lid

2. Disconnect the spark plug cap (3).

Take care to avoid damaging the spark plug wire when disconnecting the cap.

3. Clean any dirt from around the spark plug base.

Using a spark plug wrench, remove the spark plug.

4. Discard the spark plug.



  1. spark plug cap

5. Check the spark plug gap (4), using a wire-type feeler gauge. If adjustment is necessary, bend the side electrode (5) carefully.

The gap should be: 0.031-0.035 in (0.80-0.90mm)


  1. spark plug gap
  2. side electrode

6. With the plug washer attached, thread the spark plug in by hand to prevent cross-threading.

7. Tighten the spark plug:

  • If the old plug is good: 1/8 turn after it seats.
  • If installing a new plug, tighten it twice to prevent loosening:
  1. First, tighten the plug: NGK: 1/2 turn after it seats.
  2. Then loosen the plug.
  3. Next, tighten the plug again: 1/8 turn after it seats.

An improperly tightened spark plug can damage the engine. If a plug is too loose, a piston may be damaged. If a plug is too tight, the threads may be damaged.

8. Reinstall the spark plug cap. Take care to avoid pinching any cables or wires.

9. Reinstall the plug maintenance lid.

    See also:

     Honda PCX125 - Owner's Manual > Coolant

    Your scooter's liquid cooling system dissipates engine heat through the coolant jacket that surrounds the cylinder and cylinder head. Maintaining the coolant will allow the cooling system to work properly and prevent freezing, overheating, and corrosion.

     Honda PCX125 - Owner's Manual > Chassis

    Brakes The hydraulic (front) and mechanically-activated drum (rear) braking systems on your scooter dissipate the heat generated by the friction of the brake pads on the disc (front) and the brake shoes on the drum (rear) as the wheels are slowed.