The feeler gauge is a precision instrument used to measure the distance between the centre electrode and the ground electrode of a spark plug. This distance, known as the "gap", is crucial for the proper functioning of the spark plug and, consequently, of the kart engine. As the gap increases, the greater the spark ignites more fuel. But a bigger spark is harder to occur and has more chances of igniting badly. It is therefore necessary to stick to the optimal gap indicated by the spark plug manufacturer, a fact that we have researched and collected for each spark plug manufacturer and model in our dossier: Special | Spark plugs for karts: the ultimate guide with over 30 models. It is important to periodically check the gap with the feeler gauge, during the useful life-cycle of the spark plug, and if necessary bring it back to the original value indicated (using pliers and the feeler gauge). The feeler gauge is composed of a series of metal sheets of various thicknesses that allow you to accurately measure and adjust the spark plug gap. To use it, simply insert the appropriate foil between the electrodes and adjust the distance by bending the ground electrode slightly until the desired value is obtained. When choosing the thickness gauge, it is necessary to make sure that you have a "resolution" (i.e. the degree of detail of the measurement) of 0.05 mm, such as the one we propose in the link, because some spark plugs have a nominal gap of half a tenth of a millimetre, for example the Champion RCJ7Y, which has a gap of 0.65 mm.

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