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The importance of fitting the right spark plug

The article " The maintenance of the spark plug" describes how to disassemble, check and clean the candle of your Cifarelli machine.

Remember that, under normal conditions, every 100 hours of work about the spark plug must be replaced ... CHAMPION RCJ6Y, BOSCH WSR6F or NGK BPMR8Y. Remember that the type of candle is not a tip, it must be absolutely respected to avoid damage to your engine.

These spark plug are called "cold". A cold candle has the property of dissipating more heat, an important aspect as overheating would lead to a decay of performance up to phenomena of self-ignition, seizure or damage of piston, piston pin, bearings, muffler, gaskets.

In one of the Cifarelli test rooms, we "enjoyed" to mount a spark plug of incorrect type, CHAMPION CJ8Y then with a higher thermal degree, to document "what happens".

After just 40 hours of work (remember: in optimal conditions, in a clean test room, protected from dust, clean air filter, petrol and oil in the correct percentage and high quality) we disassembled and examined the engine: The photos below illustrate well what happened. The piston head is damaged in the position where the spark of the spark plug occurs and a beginning of perforation is seen. In correspondence of the visible damage in the upper part of the piston, we notice residues of burnt oil because of the excessive temperature reached.

The purple traces on the piston pin clearly show the overheating, which can cause the pin to seize and consequently the needle cage to break.

On the market there are different types of spark plug that are distinguished not only by thermal degree but also by the length of the thread, thread diameter, electrode distance and other characteristics.

Fitting a spark plug of the correct thermal degree but with an incorrect (longer) thread length, immediately causes much greater damage than those shown (rupture of the piston sky).

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