RCJ6Y is a colder plug and might be susceptible to fouling in an engine that has a RCJ8Y recommended. The Y suffix denotes an extended nose which also tends to resist fouling and is claimed to provide a better, more positive start to the flame front. In reality there is little practical difference between the standard and extended nose plug and the performance they offer in an engine in good condition and correctly tuned.
Hi, Check the depth of your existing plug from the screw part only & as long as the champion plug is not longer then it should be okay. Please leave me feed back: Malcolm Campbell, Thanks.
According to the specs on the site, the difference is one has a longer projected tip. It says that it won't HURT the machine but might result in harder to start.
Question edited for a lot more clarity, add maker, fix typos, change into what I think you were saying. Manuel is the name of a Spanish gentleman, 'manual' is the word you need.
Manuals in the link, plus the maker. This link show 'M Series' belt.
https://www.manualslib.com/manual/1865101/Lawn-Boy-M-Series.html?page=153
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