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Reading plugs....Who is correct?


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I see many articles about plug reading..... Some folks say do not read the white insulator at the top as it means nothing at all...

The main jet plug chop is done at the base of the insulator... they say the top flat part on the ring should be colored.....Light color change fully around the flat part on the lip... others say you look only at the flat lip for the color.....

 

Now, Whos correct?

 

my plugs show the flat lip as being only a 1/4 way around has changed color...indicating lean... the whole white insulator is very dark brown all the way down... Rich or lean? :)

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I think a plug chop procedure is stickied, but you need to sacrifice a new set of plugs for a wide open run to get correct readings. If you run the plugs more than that, you will not be able to read the plugs for main jet sizing. You are cutting the threads off, right? Hope this helps you!

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There is no refrence to the flat part on the plug in the sticky.... alot of other folks say this location is a good indicator for the idle/slow speed jetting.... Ill get my maginfying glass out and do some plug chops.... I cant see cutting plugs up...that would take some serious effort..... a milling machine would make it easy :)

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There is no refrence to the flat part on the plug in the sticky.... alot of other folks say this location is a good indicator for the idle/slow speed jetting.... Ill get my maginfying glass out and do some plug chops.... I cant see cutting plugs up...that would take some serious effort..... a milling machine would make it easy :)

 

Yeah, a new top-end is way less effort, lol. Grinder with a cut-off wheel and a vise. Hacksaw and a vise. Ive done it with a hacksaw and a pair of vise-grips, now THAT took some effort. $3.80 worth of plugs to take the "mystery" out of jetting your mains? Come-on, man!

Edited by black sunshine
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I see many articles about plug reading..... Some folks say do not read the white insulator at the top as it means nothing at all...

The main jet plug chop is done at the base of the insulator... they say the top flat part on the ring should be colored.....Light color change fully around the flat part on the lip... others say you look only at the flat lip for the color.....

 

Now, Whos correct?

 

my plugs show the flat lip as being only a 1/4 way around has changed color...indicating lean... the whole white insulator is very dark brown all the way down... Rich or lean? :)

 

What octane fuel do you run?

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because there are so many variences in oils and fuel additives, the plug chop, and the ground electrode are the only really reliable indicators to tell that you are dead on, save for checking for metal flecs. the rest of the range is pretty much feel, and symptoms of how it runs

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It sounds to me like the reading of the base ring is explained backwards. When jetting alky, the more the base ring is colored and the more the coloring travels down the threads of the spark plugs, the leaner you are. A rich condition will not even discolor the base, it will look rich. But, I have never read my gas plugs this way, so I can't say for sure. :confused:

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