Reading Your Spark Plugs Provides a Wealth of Information

December 10, 2010 | By: Jake Herring

Have you ever actually taken the time to read your spark plugs? I’m not talking about the gibberish scribbled on the side of the plugs. I’m saying you can read the plug by inspecting the business end. Identifying the condition of the plug will help you to troubleshoot and cure your ailing motorcycle.

Here’s what to look for when checking out the bottom of your plugs:

A grayish-tan color tells you that your spark plug is operating in the normal heat range. It also lets you know that your air-fuel mixture is correct. Check it out. This is what you want your plugs to look like.

Let’s say you pull your plug out and find excessive electrode wear. Or you’re having starting issues or experiencing misfires during acceleration. If the color of the plug is close to normal, then your plug is probably just old and worn out. You should replace it with the same heat-range plug.

If you experience detonation, you’re most likely going to find a chipped or cracked insulator when you yank out the plug. To prevent this, be sure you’re running the correct high-octane fuel and that your ignition timing is correct.

If the electrode shows pitting and wear and your insulator is chalky white, these are signs of an overheated plug. Simply change to a colder heat range to cure the problem.

Ash deposits are light-brownish deposits that cover the ground or the center electrode. This is caused by your oil or maybe fuel additives. This condition can cause misfires. Check for worn valve guides or maybe the valve seals, or try using a different fuel brand.

If your bike is smoking and you pull the plugs and find them coated in oil, it’s likely that oil is leaking past worn valve guides, piston rings — or both. You probably don’t want to hear this, but this indicates a top-end rebuild might be in your future.

This is what pre-ignition looks like — a melted or ground electrode. This is most commonly caused by a lean fuel mixture, the timing being too far advanced, or the incorrect heat range of the plugs.

Finally one of the most common problems is the carbon-fouled plug. It will be covered with black, sooty, dried-looking carbon. This condition tells you that the bike is running too rich or that your ignition is growing weak or malfunctioning.

Pulling the plugs should be the first step in troubleshooting. You can learn so much about your bike just by taking a quick read.

Comments: No Comments | Categorized Under: Tech Tips

Leave a comment