Confused on mower spark plug type

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jayjr1105

jayjr1105

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This is by far the most confused I've been when hunting a simple spark plug for a Craftsman 21" push mower with a Briggs engine.

The factory plug is a Champion RJ19HX, I currently have a Champion 5861 plug in it. I downloaded the user manual online and it claims a Champion RC12YC which has a much deeper reach.

E3 chat support said an E3.10 would be the direct replacement. Does this sound right?

[Linked Image]
 
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There are 2 types of sparkplug for B&S.....short and long thread ones...

Short is/are RJ19.....something.....ie RJ19LM RJ19HX RJ19....etc
 
I'd go by what's in the book.

... but honestly in the last couple years of me flipping mowers, I don't even replace the plugs anymore if there isn't any misfire problems. Spray some cleaner on it with a soft brush. Clean the crud off and reuse it.
 
HX is a racing plug i think it has or had a fine wire..

LM is lawn mower plug.

RJ19LM should be at wallyworld or just about anywhere.

if you want to jump to NGK- NGK BR2LM
 
How often are you replacing your spark plugs? It seems as if mowers are one area where people often completely disregard the maintenance schedule and aren't often penalized for it.
 
On older mowers , I I usually install a new spark plug , change oil , air filter and fill with new gas , every spring .

I normally run down the street , to O'Reilly Auto Parts to source a new spark plug .
 
jayjr1105,

I have found similar mistakes where the equipment owners manual does not match the engine manufacturer's recommendation. John Deere is especially bad.

I would contact Briggs and Stratton and see what they say.
 
Originally Posted by doitmyself
jayjr1105,

I have found similar mistakes where the equipment owners manual does not match the engine manufacturer's recommendation. John Deere is especially bad.

I would contact Briggs and Stratton and see what they say.

I can clearly see the empty cylinder head depth with the spark plug removed. The 10mm depth checks out. Thanks for everyone's help. BTW the NGK is a whopping $2.50 on Amazon.

Also, I change the plug every 3 years or so here in Pennsylvania. Oil gets changed every year with 10w30 along with air filter. Every 5 years I take the carb apart and clean the bowl.
 
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Get the engine number and go to the Briggs site for the engine manual.

The manual you posted shows a taper-seal plug not a gasket seal. That is entirely different.
 
on older B&S flatheads: I've been using Champion EZ start for years.

Never missed a beat with that one (and I seldom changes the plug, good for at least 3+ years of infrequent sparking).

Q.
 
??? If the plug already in it worked fine, replace with same thing (or equivalent from a different brand), though I too, find that I don't need to change mower plugs till after hundreds of hours use. I'll take out out, maybe clean it, put it back in and keep on going.
 
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All my Briggs are 10+ year old flat heads, and they (plus every Briggs I've owned for 30 years) all use the plugs shown in the picture which are "J" series Champions. 14mm threads with 3/8 inch reach. The leading "R" inidcates a resistor plug.

The model number specified in your manual is a resistor type "C" series plug which according to champion is 14mm threads with a 3/4 inch reach. Unless you have a newer model engine and it really requires this "C" plug, there is a good chance of interference with the top of the piston, especially since the Y after the heat range number indicates it is an extended tip plug.

For further confusion the plug shown in the picture is yet a different model plug with a tapered seat rather than a gasket, and based on the reach shown in the diagram it would be a "DJ" series plug. My leaf blower and chain saw has this size plug.

The only way to know for sure is to look up the correct plug based on engine model number, but I would call the manual's advice very suspicious at this point. .

.
 
Well, as fate would have it, the weather waited until today to finally dry the yard enough for my son to unbox the new mower he bought about a month ago. It has the new style Briggs 163 CC OHV engine that never needs an oil change. Low and behold, the spark plug the factory installed is the one specified in your manual. RC12YC.. Oddly enough, his manual specifies a Briggs part number for a replacement plug, not the Champion. Came with SJ SAE 30 for the "permanent" fill.
 
Originally Posted by Lou_Boyle
Well, as fate would have it, the weather waited until today to finally dry the yard enough for my son to unbox the new mower he bought about a month ago. It has the new style Briggs 163 CC OHV engine that never needs an oil change. Low and behold, the spark plug the factory installed is the one specified in your manual. RC12YC.. Oddly enough, his manual specifies a Briggs part number for a replacement plug, not the Champion. Came with SJ SAE 30 for the "permanent" fill.


You're still going to change the oil regularly in it right?
 
I have a Toro 20007 with a Tecmuseh engine that calls for RJ19LM. Started using the NGK BR2LM plugs about 8 years ago and it's still running strong.
 
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