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I was wondering the same thing this afternoon
I found lots of replacements for the Champion rc12yc but none for the yx. Are they the same spark plug? Why wouldn't anyone carry a spark plug for a lawn mower that's two years old?
Not really, but that is the only plug Sears sells as a substitute. The RC12YC plug looks like it was designed for a gap of 0.035-0.040", while the RC12YX plug was clearly designed for the recommended 0.020" gap. The RC12YC electrode is a fat cylinder like most spark plugs, while the electrode of the RC12YX is cut down to about half of the diameter. I'd guess the special RC12YX makes it easier to start the engine on a single pull.
The laser 40500 Champion cross reference is for spark plugs. There are many cross reference data bases to show which spark plugs can be interchangeable.
The Champion spark plug rj19lmc should be able to replace j19lm. Many of Champions spark plugs are interchangeable with plugs with the same letter coding.
I have autolite sparks plugs ARF32M and need to know the cross reference to NGK
A Champion RC12YC plug crosses over to several NGK plugs including a BCPR5EY, BKR6E-11, BCPR4EY, 09-06-05, BKR5E-11, ZFR5F, 09-06-04, FR5, and BK5RE.
The Champion RC12YC spark plug is one of the most preferred spark plugs. Victor series cylinder heads are also widely used especially by racers.
Both are resistive type plugs. The "R" indicates a resistor plug and the "Q" a EMS (electromagnetic suppression) resistor plug used to reduce noise in sensitive digital electronic circuits. In automotive uses Champion lists some Saab's requiring this "Q" plug. Lawn and garden small engines substituting to the RC12YC plug works just fine. In fact Sears will send you the RC12YC as a OEM part even though the engine was shipped with QC12YC plugs.
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B5s
Champion RER8YC