Spark Plug: Testing and Inspection

Spark Plug Inspection:

1. Inspect the spark plugs for:
a. Improper gap
b. Carbon deposits
c. Cracked center electrode insulator
d. Burned or worn electrodes (may be caused by):
- Excessive mileage
- Lean fuel mixture
- Advanced ignition timing
- Loose spark plug
- Plug heat range too high
- Insufficient cooling

e. 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
- Clogged air cleaner element
- Deteriorated ignition coil, coil wire or ignition wires

2. Replace the plug if the center electrode is rounded.

Spark Plug Gap:

3. Adjust the gap with a suitable gapping tool.
Electrode Gap: 0.8-0.9 mm (0.031-0.035 in)