The article “Spark plug maintenance” describes how to disassemble, check and clean the spark plug of your Cifarelli machine.
It is also remembered that “sometime” the spark plug must be replaced…with the list of the typology of spark plugs that “MUST BE” mounted: CHAMPION RCJ6Y, BOSCH WSR6F or NGK BPMR8Y. Remember that the spark plug typology isn’t an advice; it must be absolutely respected to avoid any engine damages.
These spark plugs are defined “cold”; a cold spark plug has an higher dissipating property of heat, a very important aspect because the overheating causes a degraded performance, till arriving to auto-ignition, seizure of the piston or damages to piston pin, bearings, silencer and gaskets: in short, a disaster!
In Cifarelli factory, in one of our test room, we “had fun” to mount a wrong kind of spark plug like the CHAMPION CJ8Y, then with a higher heat rating, to report “what happens”.
After just 40 hours of working (remember: under optimal conditions, in a tidy test room, protected from dust, with a well clean air filter, with gasoline and oil of high quality and correct proportions) we disassembled and examined the engine: the pictures below show very well what happened. The piston head is damaged in the position of the spark plug spark; it shows a beginning of perforation.
At the bottom of the piston, just in correspondence of the visible damage in the upper part of the piston, you can see residues of burnt oil caused by the excessive temperature reached. Purple traces present on the piston pin clearly show the overheating; it may cause the seizure of the pin and consequently the breaking of the needles cage.
I want to remember that on the market there are different kind of spark plugs which are different not only for heat rating but also for the thread length, diameter of the thread, electrodes gap and other characteristics. Mounting a spark plug with correct heat rating but with a longer length of the thread immediately causes much more damages compared to those illustrated (rupture of the piston top).
I recommend: when you will verify your Cifarelli engine spark plug, don’t hesitate to replace it if of a different type from those I have mentioned.