Spark Plug: Testing and Inspection

Spark Plug Inspection





1. Inspect the electrodes and ceramic insulator for:
- Improper gap
- Oil-fouling
- Carbon deposits
- Cracked center electrode insulator

Burned or worn electrodes may be caused by:
- Lean fuel mixture
- Advanced ignition timing
- Loose spark plug
- Plug heat range too high
- Insufficient cooling

Fouled plug may be caused by:
- Rich fuel mixture
- Retarded ignition timing
- Oil in combustion chamber
- Incorrect spark plug gap
- Plug heat range too low
- Excessive idling/low speed running
- Faulty automatic choke Carbureted engine)
- Clogged air cleaner element
- Deteriorated ignition coil or ignition wires





2. Clean the electrodes with a spark plug cleaning machine, or with a wire brush. Clean between the outer shell and center insulator with a stiff wire as shown. Clean plug threads with a wire brush.





3. Replace the plug if the center electrode is rounded as shown.

Standard Plug:
BPR5EY-11 (NGK), W16EXR-U11 (ND)
(for all normal driving)
BPR6EY-11 (NGK), W2OEXR-U11 (ND)
(for hot climates or continuous high speed driving)

4. Adjust the gap with a suitable gapping tool.

Electrode Gap: 1.0 - 1.1 mm (0.039 - 0.043 in.)

5. Screw the plugs into the cylinder head finger tight, then torque them to 18 N.m 11.8 kg-m, 13 lb-ft).

NOTE: Apply a small quantity of anti-seize compound to the plug threads before installing.