11 Things Your Spark Plugs Are Telling You | Outdoor Channel
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11 Things Your Spark Plugs Are Telling You

By: myatvblog.com

Permitted use provided by: myatvblog.com

One of the best things my father taught me was engine maintenance. My dad would examine every spark plug he ever removed from an engine on our farm. It turns out, the spark plug tells the story of your engine.

The color of your spark plug is a valuable piece of information, it tells you how well your ATV is really running. By examining the insulator firing nose color, a mechanic can determine a great deal about your ATV engines overall operating condition.

A light tan/gray color tells you the spark plug is operating at optimum temperature and the engine is in good condition. Dark coloring or heavy black wet or dry deposits can indicate rich condition, too cold a heat range spark plug, a possible vacuum leak, low compression, overly retarded timing, or too large a plug gap.

A wet spark plug is usually an indication of a leaking head gasket, leaking rings, valve-train issues, or an extremely rich condition. The nature of the liquid on the firing tip will help you diagnose your problem.

Signs of fouling or excessive heat must be quickly traced to prevent further deterioration of performance and possible engine damage.

Normal Condition
Dry and Wet Fouling
spark plug overheating Overheating
Lead Fouling
Lead fouling usually appears as yellowish brown deposits on the insulator nose. This cannot be detected by a resistance tester at room temperature. Lead compounds combine at different temperatures. Those formed at 370-470°C (700-790°F) having the greatest influence on lead resistance.
Normal Life
A worn spark plug not only wastes fuel, but also strains the whole ignition system because the expanded gap (due to erosion) requires higher voltages. Normal rates of gap growth are as follows:
Four Stroke Engines: 0.01~0.02 mm/1,000 km (0.00063~0.000126 inches/1,000 miles) Two Stroke Engines: 0.02~0.04 mm/1,000 km (0.000126~0.00252 inches/1,000 miles)
Abnormal Erosion
Erosion, Corrosion and Oxidation
Lead Erosion

NGK Spark Plugs has a FAQ page that answers many of spark plug questions.

Original article: http://myatvblog.com/atvrepair/11-spark-plugs-telling/

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