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Spark Plug Education

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Spark Plug Education

Postby Mr Mower Man » Tue Oct 31, 2017 2:39 pm

I want to know more in general about spark plugs, the NGK and Champion numbering systems (those are the 2 brands I use), and what sorts of "conversions" between plugs are OK without damaging the engine or creating performance issues. I just found some information on heat ranges, which I think I understand pretty well now. But I don't know, for instance, if it's OK to use a resistor plug in an application that calls for a non-resistor. I did learn that it's generally a no-no to use a non-resistor in place of a resistor, but is using a J19LM in a pushmower OK, even when it calls for an RJ19LM?

I have a Homelite Super XL chainsaw in my shop right now, and the Champion catalog I have calls for a CJ6 plug. I don't have any CJ6's in stock, but I do have a few RCJ6Y plugs. Heat range is the same, thread size and reach is the same. But I don't know what sorts of changes the resistor will make in the engine performance. Also, the Y on the end. According the the Champion numbering system chart I'm looking at, the RCJ6Y has a "standard projected core nose" firing end design, whereas the CJ6 has a "conventional" firing end design. So what does all that mean and what difference does that make?

I know some of you on here know this stuff. What would you recommend I read to become a spark plug expert?
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Re: Spark Plug Education

Postby bgsengine » Tue Oct 31, 2017 4:06 pm

Mr Mower Man wrote: Also, the Y on the end. According the the Champion numbering system chart I'm looking at, the RCJ6Y has a "standard projected core nose" firing end design, whereas the CJ6 has a "conventional" firing end design. So what does all that mean and what difference does that make?
?

center electrode is projected - sticks out further - liable to punch a hole in the piston when a non-Y is called for CJ8 can work (but heat range will be a bit off)

Heat range has to do with how far (or long) the insulator is from the tip to the plug body where heat dissipates to.. Colder plugs have shorter insulator (they cool faster) If you see a plug that is consistently getting fouled sometimes running a heat range or two hotter can help that.. but too hot of a plug can cause combustion issues (pre-ignition) and overheating the engine

Resistor plugs are mostly for EMF suppression (KE4 being a HAM radio guy can tell you about that) which is why much of the stuff in Canada *requires* a resistor plug. There's no real problem most times with going between resistor to non-resistor , although *some* ignition systems can experience issues with EMF using a non-resistor plug, and some are equipped with a resistor cap plug boot and then may have ignition issues if they are designed for non-resistor plugs. Then you get down to the choices in electrode configurations (center wire material,electrode shape, etc, ground electrode may have a U or V shaped groove, then there's platinum and Iridium electrodes, and so on - many of those can also work fine in a "like" application even though they were designed originally for specialized (performance, racing, etc) purposes - For example, the common RC12YC used in many Briggs OHV engines - NGK has a diverse selection all within the same heat range and will fit up and work perfectly but have different performance characteristics. Both NGK and Champion have online product catalogs you can look up plug for an application.
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Re: Spark Plug Education

Postby Mr Mower Man » Tue Oct 31, 2017 7:29 pm

bgsengine wrote: CJ8 can work (but heat range will be a bit off)

I actually did put a CJ8 in it just to figure out that the original spark plug was the reason it didn't run. I was afraid to leave it in there, though, for the reason you said. I think I'll compare the CJ8 with the RCJ6Y to see how much the lengths differ. Interesting stuff!
bgsengine wrote:For example, the common RC12YC used in many Briggs OHV engines - NGK has a diverse selection all within the same heat range and will fit up and work perfectly but have different performance characteristics.
I do have a few RC12YC plugs in stock, but I almost always use the NGK CS6 plugs for Briggs and Kohler OHV engines. Main reason I started using them was the great deal I got on them on a stocking order. I think they work great. Never had any problems. What are your plugs of choice for this application?
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Re: Spark Plug Education

Postby creia » Tue Oct 31, 2017 9:33 pm

We have been using ONLY NGK plugs in all of our small engines and motorcycles for some time. We WERE using Champion, however, about 5 years ago starting getting "duds" that were brand new. We switched to NGK, never looked back, and have had ZERO problems or "duds" since. Around here (Southern California) I have noticed that all the small engine and motorcycle repair shops are using NGK- most likely for a very good reason. I am (very easily) old enough to remember when Champion was the "gold standard" for spark plugs in anything with an engine- sadly, it appears that is is no longer the case...
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Re: Spark Plug Education

Postby Skywatcher » Tue Oct 31, 2017 11:27 pm

Hi Mr. Mower Man

The best way I've ever heard the heat range of a spark plug described was on the old PERR forum and I use this analogy to explain the heat range to my customers.

When a spark plug is of the correct heat range, the center electrode gets to the same temperature as the inside of a self cleaning oven so keeps itself clean. If the plug is too cool, it won't self clean so gets fouled up with carbon. If the plug is too hot, it glows red hot and works like a glow plug causing pre-ignition and engine damage. If the center electrode and porcelain of the plug is light brown to pale tan, everything is as it should be and your engine is running at its best.

Up here at 3,500 feet above sea level, I've found that using the next higher heat range of spark plug from what the manufacturer recommends, works best on engines with non adjustable carburetors as a slightly rich burn equates to a slightly cooler burn. On engines with adjustable carburetors, simply adjust the carburetor for optimum performance and the rest looks after itself. Hope this helps you in your ongoing quest for knowledge,

Sky
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Re: Spark Plug Education

Postby KE4AVB » Wed Nov 01, 2017 9:50 am

creia wrote:We have been using ONLY NGK plugs in all of our small engines and motorcycles for some time. We WERE using Champion, however, about 5 years ago starting getting "duds" that were brand new. We switched to NGK, never looked back, and have had ZERO problems or "duds" since. Around here (Southern California) I have noticed that all the small engine and motorcycle repair shops are using NGK- most likely for a very good reason. I am (very easily) old enough to remember when Champion was the "gold standard" for spark plugs in anything with an engine- sadly, it appears that is is no longer the case...
Michael

I had fairly good luck with NGK except the CMR6H and CRM7H which do fail a lot. And you will have failures from anywhere from completely dead to firing causing extreme knocking. I even had a couple that would only fail under heavy loads. I go through more of them then any other plug here.

I had a customer a couple years ago that swore he had a rod problem with his blower because of the knocking from pre-ignition and was pissed because I only replaced the expensive spark plug to resolve the problem.
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Re: Spark Plug Education

Postby Dale_W » Mon Oct 15, 2018 6:56 am

Hello All
I thought I'd revive this thread started by Mr. Mower Man.
My interest is not in heat range or manufacturer of the plug, but in the use of a resistor plug.

I get that a non-resistor plug can cause radio interference. But can using a non-resistor plug in place of resistor plug cause any damage to the engine or ignition system?

My specific case is a Briggs 126T02-0220-B1 071023 58 mounted on a toro lawnmower. The original plug was an RJ19LM. I have new J19LM just waiting to be used.

Of course I can stop on the way home from work and pick up an RJ19LM plug.

Just looking to get a little smarter today.

Thanks

Dale

EDIT: This is mildly interesting. The blister pack for an RJ19LM lists these other types:
J19LM
RJ19LMC
RJ2YLE
799876
RJ2YXLE
and I'm having trouble reading it..019-3387-2

So clearly Champion is telling my I can use the J19LM in place of the RJ19LM, or wait, maybe they are telling me I can use the RJ19LM in place of the J19LM. :)
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Re: Spark Plug Education

Postby bgsengine » Mon Oct 15, 2018 8:11 am

Dale_W wrote:Hello All
I thought I'd revive this thread started by Mr. Mower Man.
My interest is not in heat range or manufacturer of the plug, but in the use of a resistor plug.

I get that a non-resistor plug can cause radio interference. But can using a non-resistor plug in place of resistor plug cause any damage to the engine or ignition system?

My specific case is a Briggs 126T02-0220-B1 071023 58 mounted on a toro lawnmower. The original plug was an RJ19LM. I have new J19LM just waiting to be used.

Of course I can stop on the way home from work and pick up an RJ19LM plug.

Just looking to get a little smarter today.

Thanks

Dale

EDIT: This is mildly interesting. The blister pack for an RJ19LM lists these other types:
J19LM
RJ19LMC
RJ2YLE
799876
RJ2YXLE
and I'm having trouble reading it..019-3387-2

So clearly Champion is telling my I can use the J19LM in place of the RJ19LM, or wait, maybe they are telling me I can use the RJ19LM in place of the J19LM. :)


Actually the blister pack you are looking at is for the RJ19LMC probably stock number 5861 the EZ Start one-tug-plug packaging

The C indicating copper core electrode, gapped to .020 which is the only approved plug on some of the newer emissions compliant engines..

There's only a few applications where the resistor plug is required for proper ignition operation, but none on Briggs engines. Can use the J19LM or the RJ19LM interchangeably with no issues... If you are a stickler about making sure to maintain EPA emissions compliance, then you will want to make sure of getting the RJ19LMC for those engines requiring it, however.
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Re: Spark Plug Education

Postby Dale_W » Mon Oct 15, 2018 8:34 am

perfect answer sir, thank you!
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