Tech bit: Spark plug that ignite

Even though the average spark plug has undergone a lot of modification they still look very much the same as those of a decade ago. The modern spark-plug is normally one-piece construction. Rough handling when removing or resenting is likely to break the ceramic insulator. To remove the plugs, first detach the high-tension leads and […]

Even though the average spark plug has undergone a lot of modification they still look very much the same as those of a decade ago. The modern spark-plug is normally one-piece construction. Rough handling when removing or resenting is likely to break the ceramic insulator.

To remove the plugs, first detach the high-tension leads and mark them so that they can be replaced in the right order. Be mindful that you don’t mark the leads by notching them- this damages the insulations. If the plug has been properly fitted it won’t take much effort to unscrew it. It’s best to use box or socket spanner.  Ensure that the spanner is fully pushed home, but make certain that it is not tilted to one side, as this may break the ceramic insulator.

When the plug has been thoroughly cleaned and its gap reset, lightly lubricate the thread with oil before replacing it in its cylinder-blocking housing.

Screw in the plug by hand as far as possible, completing the job with a socket or box spanner, again bearing in mind that sideways movement on the spanner is to be avoided.

Never over-tighten spark-plugs; it can make them extremely difficult to remove again-particularly those with tapered seats and no gasket. In light alloy engines, over-tightening may damage the threads, calling for an expensive repair.

When replacing plugs, ensure that the new ones are of the recommended heat range for the engine. This is particularly important when plugs of a different make have to be fitted. The wrong plugs, especially on high-speed trip, can cause extensive damage.

Cleaning tips for spark plugs

1.    Clean around the base of the plug with soft brush

2.    Avoid damaging the insulator

3.    Clean oily plugs white spirit and have them abrasive-blasted by a mechanic. Avoid using wire brush. It is not recommended.

4.    File down irregularity on the electrode until they are flat which involves resetting the electrode gap.