Tech Tips

Cleaning and Re-Gapping Spark Plugs

Written by  May 31, 2006

We have all been exposed to that fouled out spark plug due to contaminated fuel or riding with the choke on too long. When this happens, usually we are not equipped to remove and replace the spark plug.

This is not bike-specific to just dirt bikes and two-stroke applications; this can happen to all motorcycles. Harley owners may not realize this, but Harleys require a longer choke time than most metric bikes. They also will run richer just cruising around so they are more susceptible to fouling the plugs out quicker. If you have ever had this problem, you know all too well that the engine may pop or backfire, and with a four-cylinder engine you can actually feel the cylinder miss out and lose power.

The only thing to do at this point is either replace the plug with a known good one or clean the plug that is currently being used. If you choose to replace the plug with a new one, that’s fine; you will want to set the electrode gap with a wire-type spark plug gap tool. One other item is to coat the threads with anti-seize which will help with removal the next time you are inspecting the plugs.

I have cleaned plugs in the past with a nylon brush and solvent; this will work; however, I do not use this method any longer. I purchased a media blast-type cleaner that uses compressed air to clean the plug back to new condition. Everyone has a budget and tools of their choice, so I am telling you what works for me. Media blast-type cleaners actually do a great job and they can be used hundreds of times which save you money.

This type of cleaner is a fairly inexpensive tool and can be portable as well, so it is not only a smart way to clean spark plugs, it is the right way to do it. Once you have removed the spark plug carefully, inspect the plug, note the color of the porcelain and the electrode tip. If the porcelain is cracked or damaged, throw that plug away. If the electrode is just worn or rounded this too must be discarded. Plugs that have a nice electrode and are just fouled can reused again.

Hook up the air compressor line to the cleaner and place the spark plug in the opening. While holding the plug, push the air button and clean the plug. This usually takes about 10 to 20 seconds to clean depending on your air pressure rating. Depress the air button and remove this from the cleaner.

Carefully inspect the plug. What you will notice is the plug is in like-new condition and can be used immediately. I do recommend that you use contact cleaner to wash the plug from the media dust. You will find that this system is a great way to help you in the jetting process and a great way to monitor engine condition in the event the engine starts to pass engine oil past the rings or the valve seals.

I think once you have used this system you will agree that this cleaner is a lifesaver and will save you time on cleaning the plugs. After you have cleaned the plug, re-gapping is the final step to the cleaning process. You will want to use a wire-type gapping tool that can be purchased at any auto parts store or equivalent. These will not damage the electrode of the plug and are the best, accurate way to gap according to the service specs of your motorcycle. The plug gap specs are in the tune-up procedure in your service manual.

That’s about it on the cleaning of spark plugs. Rest assured they will need to be cleaned or replaced at the designated service intervals. Cleaning plugs gets a whopping 2 on the tough-o-meter scale because you have to be careful not to cross thread the spark plug hole when reinstalling.

B-safe out there!

Dave Miller