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TKART magazine Expert Advice | Kart spark plug assessment (and advice from real professionals for its maintenance)
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Mattia Livraghi
20 March 2023 • 11 min. read
“In addition to affecting engine performance, spark plugs, thanks to the colour that their parts take on, allow you to assess carburetion”
Three spark plugs in three different states of use: starting from the left, after cleaning with a brake cleaner, after sandblasting and finally a new spark plug.

If the 2-stroke engine is the heart of a kart, spark plugs are the electrical impulse which (with its ignition) allow it…. To beat. In fact, the spark they generate is essential for the ignition of the engine and for its operation (for more information, read "Technique - The spark plug"). In addition to affecting engine performance, spark plugs, thanks to the colour that their parts take on, allow you to assess carburetion. It is therefore a prerogative of every kart driver to know how to correctly interpret and manage this component, as small as it is essential. After pointing out the equipment (and related expedients to be applied) useful for making it work correctly (read "Must Have - 4 expedients for a spark plug ... On top form"), we once again turned to Massimo Aceto, a professional mechanic from the Birel team ART in international kart competitions and owner of the ACE Racing team, precisely to understand how to analyse them when you want to check the carburetion and how to carry out their correct maintenance.

A spark plug removed from the engine head and held in a hand to assess carburetion.

1 Why can the spark plug be an indicator of engine carburetion?

The spark plug is one of the engine components that can be analysed to gather information about engine carburetion. In fact, carburetion (i.e. the process that regulates the contribution of the mix between mixture and air in the combustion chamber of 2-stroke kart engines, editor's note) has a direct effect on the spark plug, "colouring" its surfaces. Consequently, the analysis of the latter can give fundamental information to understand whether carburetion has been done in a workmanlike manner, or if it needs further adjustments. In fact, carburetion is a fundamental check to avoid causing damage to the engine and to ensure that the potential of the engine is exploited to the maximum. For example, carburetion that is too rich (with an excess of mixture in the air/fuel mix) "throttles" the engine and makes it less incisive, while carburetion that is too lean (with a lack of mixture in the air/fuel mix), prevents correct lubrication and, in addition to causing a drop in performance, it risks causing breakage. It is therefore useful to check the spark plug when in doubt about carburetion, but it is advisable to assess it constantly, ideally at the end of each track session. What is advantageous is that removing the spark plug cap and then unscrewing the component from its housing is an extremely simple and quick activity, unlike what happens when you wish to assess carburetion on a piston crown, using the appropriate torches ( or flexible endoscopes) or by dismantling the canister.

2 What parts of the spark plug do you need to "assess" to analyse carburetion?

A visual analysis is sufficient to assess the carburetion from a spark plug. Looking at the part of the spark plug that is inserted into the engine, the outer ring indicates the carburetion trend at low engine speeds, in the range from zero to nine thousand rpm. On the other hand, the ceramic centre shows the carburation at high revs, when the engine works above nine thousand rpm. Mainly, there are two aspects to consider when carrying out an assessment: the colour and the possible presence of residues of unburned oil.

The outer ring of the spark plug reveals carburetion at low engine speeds (0-9,000 rpm). The central ceramic part, on the other hand, indicates carburetion at high engine speeds (> 9,000 rpm).
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