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TKART magazine Special | Spark plugs for karts: the ultimate guide with over 30 models
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Gianluca Covini
08 September 2023 • 37 min. read
We analysed and described the products of the most well-known brands in motorsport (NGK, Denso, Brisk, Bosch, Champion, E3 and Autolite) to help you find your way around a truly diverse market. We also provide you with all the information to recognise the differences between one product and another, so as to always be ready to choose the one that best suits your needs (and especially those of your engine)


In addition to playing a central role in the combustion process of an engine (to learn more we recommend the article "Technique | spark plugs"), in kart engines the spark plugs are continuously subjected to many stresses (from the number of sparks fired at high speeds, up to the high temperatures to which they are subjected), which can, at any time, affect their correct functioning. This is why (to avoid finding yourself with unpleasant surprises just when you get on a track), one of the first features to look at to choose a spark plug is the brand. In fact, opting for consolidated brands in motorsport (and not only) will allow you to have reliable products that can ensure constant operation. In this article, we analyse and highlight the differences between spark plugs, specifically designed for the needs of kart engines of the 7 leading brands in this sector. Here are the ones examined.
NGK Spark Plug
Founded in Japan in 1936, NGK, an acronym for "Nippon (Japan) Gaishi (insulator) Kaisha (company)", is the world's leading manufacturer of spark plugs for the entire internal combustion engine industry. Also with regard to the karting sector, NGK spark plugs are the best selling products and are a reference point with regard to their quality level. It is no coincidence, therefore, that in order to identify the thermal grade of a spark plug, the scale used by NGK is a real reference point, also used to measure the thermal grade of spark plugs of other brands: in fact, as we will highlight later, as regards thermal grades, each company has a different measurement method.

Here are the NGK Spark Plug spark plug series that we analysed:

- B EG
- R7282
- R6252
Brisk Tabor is a joint-stock company with capital solely from the Czech Republic. Although it was officially founded in 1992, following the privatization of the state-owned company Jiskra, the Brisk brand has its roots in 1935, when the Brisk plant was founded in the Czech town of Tabor (which is still the location of the Brisk plants) BRITA, a company that makes spark plugs. The Brisk racing sector has several collaborations with the most important brands in motorsport. As far as karting is concerned, the spark plugs of the Czech company are original equipment for various TM Kart engines (such as the KZ-R1 and the KZ-R2); moreover, Brisk produces the Freeline brand spark plugs (the kart accessories line of the Birel ART group) for BMB engines (Birel ART's engine rib).

Here are the series of Brisk Racing spark plugs that we analysed:

- L S
- L LS
- D IR
Denso Corporation
Founded in 1949, Denso Corporation is a multinational corporation headquartered in Japan with 35 offices and more than 165,000 employees worldwide. It provides thousands of automotive solutions and holds over 42,000 patents. Denso is also a world leader in iridium spark plug technology.

Here are the Denso Corporation spark plug series that we analysed:

- IW
The German multinational Bosch is one of the best-known companies in the automotive industry and is the world's largest manufacturer of car components. It has been manufacturing spark plugs since 1902 (a little curiosity: it was the founder of the company, Robert Bosch, who invented the first spark plug for internal combustion engines) and today the market coverage of vehicles with Bosch spark plugs in Europe is about 90%. In the karting sector, however, the diffusion of Bosch spark plugs has not yet had the same success and in the present day they are not widespread, in terms of use, among motorists and enthusiasts.

Here are the Bosch spark plugs series that we analysed:

- W CS
- WS F
Similarly to Bosch, Champion is one of the most important brands in the production of spark plugs, but in the karting sector they are not widely used (they are used as original equipment for Briggs & Statton or as spare parts for Comer engines). Founded in 1907 in the United States of America, Champion is part of the American Tenneco group, specialised in the supply of original equipment and aftermarket components for the automotive sector.

Here are the series of Champion spark plugs that we analysed:

Autolite, also known as Auto-Lite, is a famous American brand that sells spark plugs and sets of ignition cables. The company was founded in 1911, but spark plugs were produced only from 1935. Autolite products are available in the United States, Canada, Mexico and Australia, but can also be purchased online. Until 2011, the Autolite brand was part of the Honeywell Group, later it was absorbed by FRAM Group, an investment company based in New Zealand. Since April 2000, Autolite has been the official spark plug of NASCAR.

Here is the Autolite spark plug that we analysed:

- AR3910X
E3 Spark Plugs
E3 (meaning "Efficiency, Energy, and Ecology") is an American brand specialised in the production of spark plugs and spark plug cables. After investing in years of research, the company developed the "DiamondFIRE" mass electrode, which has a particular conformation, different from the classic "J" design, designed to improve the quality of the spark, reduce the formation of deposits and the wear of the electrodes. E3 spark plugs are chosen as original equipment by Tillotson for its engines.

Here is the E3 spark plug that we analysed:

- E3.106


Choosing a spark plug is far from an easy task because there are so many variables to take into account. Among these, without a shadow of a doubt, the construction characteristics of each product are the first discriminating factor to understand whether a spark plug is suitable, or not, for your kart engine. But not only that, knowing the precise characteristics of each spark plug will allow you to install them correctly in their housings and to always have the state of wear under control. How so? We describe it in this slide.
If you have a kart engine made without taking into account the approval regulations imposed by FIA Karting (to learn more about this topic we recommend, "Dossier | FIA approvals: what they are, what they are for, how long they last... the ultimate guide!"), our advice is to consult the manual provided by the manufacturer of your engine, since each brand may opt for different sizes. If, on the other hand, you have an engine produced according to the dictates of the CIK-FIA regulations, then it is the FIA Karting regulation that imposes precise "sizes" on manufacturers, including spark plugs. Specifically, all spark plugs must have a thread with a diameter of M14 with a pitch of 1.25 mm. As regards, however, the length of the threaded part inside the cylinder head is fixed at 18.5 mm. Thus, the length of the thread of the male spark plug is 19 mm (0.75 inches), so that combustion takes place inside the chamber. The female thread of the spark plug in the cylinder head can also be replaced by a threaded insert. Regarding the protrusion of the ceramic insulator, the FIA regulations state that the insulation of the electrode (not including the electrode itself) must not protrude beyond the metal body of the spark plug. The insulation (usually white), must not, therefore, come out of the metal ring that is beyond the end of the thread.

In summary, kart spark plugs must comply with the FIA technical regulations, which impose the following measurements:

Thread diameter: M14Thread pitch: 1.25 mm
Female thread cylinder head length: 18.5 mm
Spark plug thread length: 19 mm
Notes: no protrusion of the ceramic insulator from the metal body (as per Appendix 5 of the FIA Karting technical regulations)

By checking the technical data sheet to ensure the sizes correspond to those of the regulation, you will not have problems either in assembly or during the technical verification of your kart during race weekends.

The illustration shows the main sizes of spark plugs: [A] thread diameter; [B] thread length; [C] thread pitch; [D] protrusion of the insulator (which according to FIA Karting regulations must not protrude beyond the metal body of the spark plug).
Appendix 5 of the FIA Karting Technical Regulations prescribes the manufacturing guidelines regarding the protrusion of the insulator.
Comer C50, C52 and W60 engines are made not taking into account FIA Karting regulations, therefore they require ad-hoc spark plugs for their operation. We will indicate them in detail in this article.
The size of the spark plug hexagon (i.e. the element that allows you to impress the tightening torque of this element on the engine head) is a parameter that always needs to be taken into consideration, especially with regard to compatibility with the key for the spark plug you have available (the advice, however, is always to have a torque wrench, one of the precautions for the management of spark plugs absolutely to know, which we have described in the article "Must Have | 4 precautions for a spark plug... At top performance!"). Most spark plugs have a 20.8 mm (13/16") hexagon, often rounded to 21 mm, being the distance between two parallel faces of the hexagon. There are also other sizes: for example, 16 mm (5/8"), used on the NGK 7282 low spark plug; or, less common, 19 mm (3/4").
The infographic has a summarised explanation of how much to turn the spark plug once it has arrived at a stop on the cylinder head, screwing it in first by hand if it is new (from 180° to 240°) or used (30° is enough). It refers to spark plugs with a thread diameter of 18 mm or 14 mm, such as that of karts. To be more precise, you need a torque wrench following the tightening torque indicated by the manufacturer (see the spark plug cards in this dossier).
The "Gap" refers to the distance between the central electrode and the ground electrode. As the gap increases, a larger spark ignites, igniting more fuel. On the other hand, it is more difficult for a larger spark to be generated and there is more chance of poor ignition (resulting less intense). It is not a parameter of choice by the end user, because each spark plug has its optimal gap to which you must adhere. However, it is important to periodically check the gap with a thickness gauge, during the life-cycle of the spark plug, and possibly bring it back to the original value indicated (using a clamp and a thickness gauge).
The "gap" is the distance between the central electrode and the ground electrode.
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