# Resistor vs Non Resistor plugs



## Minreg (Jan 1, 1970)

All of my plugs seem to be of the resistor type.
Just figured out the R in RDJ7Y must stand for resistor.
I bought the only one I could find which was just DJ7Y.

*Should I use the type that came out of my equipment or this other type that is available?*

Both mower shops I used before are no longer in biz.
So if this is the wrong type of plug I will check the auto parts store or online.
Really why do I leave the house...


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## pyro_maniac69 (Aug 12, 2007)

some companies recommend a resistor plug, but it is not necessary, the only thing a resistor plug does is stop static from being produced aka, if your old school and are listening to the radio when you are using a small engine, a non resistor plug will give you a buzzing sound, a resistor plug will not


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## billsmowers (Mar 21, 2008)

i thought it as also to do with interferance with elecronic ignitions as well i remember seeing in the trade mag we get here in the uk thi if a non resistor plug is fitted in place of a reistor one the warrenty will be void due to damage to the electronics in the coil


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## paulr44 (Oct 14, 2008)

billsmowers said:


> i thought it as also to do with interferance with elecronic ignitions as well i remember seeing in the trade mag we get here in the uk thi if a non resistor plug is fitted in place of a reistor one the warrenty will be void due to damage to the electronics in the coil


In general, resistor plugs, or resistor wires serve to protect nearby electronics from working correctly. As for the interference possibly damaging them, I have my reservations - you'd have to read up on that.

See NGK's info:
http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqresistor.asp


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## paulr44 (Oct 14, 2008)

*electronics from working correctly*
should read "INcorrectly"


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## billsmowers (Mar 21, 2008)

paulr44 said:


> In general, resistor plugs, or resistor wires serve to protect nearby electronics from working correctly. As for the interference possibly damaging them, I have my reservations - you'd have to read up on that.
> 
> See NGK's info:
> http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqresistor.asp


i was informed sthl would void any warrenty claim if a non resitor plug was fitted
this is what i was told by a stihl rep

bill


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## pyro_maniac69 (Aug 12, 2007)

might be because they are afriad of it damaging the coil

but I don't believe they do that that much


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## paulr44 (Oct 14, 2008)

Some of the newer Stihl engines have a spark retard control built into the coil. Some, like Kohler, call it a spark advance but you can't advance timing if the coil doesn't move. You can, hold the spark back at lower RPM and allow it to advance to "non adjusted" timing, which in my book equates to a RETARD control.
Anyway, if you're unsure if a Stihl coil is such controlled, look at the price. Standard coils are about $50 U.S. and the retard-control coils are about double that.
Also, they now use a solid-state fuel "control" system on such saws as the MS361.
Paul


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