Spark plug reading question.

Brian S · Nov 22, 2008

Here is a situation.

Lets say you pull your plug and check color, you find it is a bit brown because you a little rich. You lean it out some and run a few tanks through it but when you check again it is the same color. Will the plug ever change color back to whitish gray or once the plug gets brown/black is it stained forever?

I understand you usually read a brand new plug, not one thats been used for a while but I thought I would throw this one out there.

Thanks,
Brian

breymeyerfam · Nov 22, 2008

the correct color of the plug shold be a little brown, carmel colored. white is lean.

Brian S · Nov 22, 2008

I understand, that was not the question though.

ShoerFast · Nov 22, 2008

Just my $0.02 cents

I would not like even a gray-brown if a tad richer would give a nice tan-brown.

Brian S · Nov 22, 2008

ShoerFast said:
Just my $0.02 cents

I would not like even a gray-brown if a tad richer would give a nice tan-brown.

OK, I understand what color we are shooting for, forget I said gray or white.

This is my question.

Will the plug ever change color back to (insert favorite color here) or once the plug gets (darker than it should) is it stained forever?

yo2001 · Nov 22, 2008

the plug will change back but not fast enough to tell the mixture. IMO

I usually take the load off in cut every now and then and make sure that the saw is still slightly 4 stroking

blsnelling · Nov 22, 2008

You're probably looking at the wrong area of the plug. The color that really matters is down at the base of the porcelan where it's difficult to see. Also, it's of no value unless it been running WOT in the cut and shut off without any idle time. Set it with a tach and leave it unless it's a modded saw.

ShoerFast · Nov 22, 2008

Yes, a very brown porslen will turn to a lighter color with heat. Just a a lean plug will turn darker in time.

Darker the better in my book, better fouling a plug instead of waisting a jug.

Brian S · Nov 22, 2008

The reason for the question was that today while cutting my 026 was 4 stroking too much in the cut so I leaned it a fraction of a twist and it settled back into a nice 2 stroke under load. I ran three tanks through today and when I was cleaning the saw I pulled the plug, it was uniformally dark brown with a streak of light brown caramel on one side leading down the porcelin insulator. I had checked the plug last week and it looked virtually the same hence my question about color changing. I think my tuning is perfect I was curious about it changing color.

Thanks to all who responded.

Oh yeah, a tach is going to be my xmas gift to myself! I have one saw that is so quiet I can't seem to dial it in by ear.

Stihl051master · Nov 22, 2008

To answer your original question - yes. If you are running too lean it will lighten the plug color up to a light gray in a hurry, but hopefully you'll notice before it's too late! (and expensive)

820wards · Nov 22, 2008

Brian S said:
OK, I understand what color we are shooting for, forget I said gray or white.

This is my question.

Will the plug ever change color back to (insert favorite color here) or once the plug gets (darker than it should) is it stained forever?

Brian,

I raced cars for many years and when we did plug checks it was always with new plugs because, YES the porcelain will stain. As with previous reply's, you are looking for a light caramel brown color when using mixed fuel.

jerry-

blsnelling · Nov 22, 2008

I'd much rather see cocoa brown myself. Anything less is too lean in my books.

volks-man · Nov 23, 2008

Brian S said:
The reason for the question was that today while cutting my 026 was 4 stroking too much in the cut so I leaned it a fraction of a twist and it settled back into a nice 2 stroke under load. I ran three tanks through today and when I was cleaning the saw I pulled the plug, it was uniformally dark brown with a streak of light brown caramel on one side leading down the porcelin insulator. I had checked the plug last week and it looked virtually the same hence my question about color changing. I think my tuning is perfect I was curious about it changing color.

Thanks to all who responded.

Oh yeah, a tach is going to be my xmas gift to myself! I have one saw that is so quiet I can't seem to dial it in by ear.

would that be the cs440? that saw is the reason i bought a tach. after a muff mod it wasn't any easier.

BobL · Nov 23, 2008

Yesterday I finally got to set the tuning on my 066 BB saw using a tacho . I warmed it up and set it for 13000 and cut cookies for about half a tank. I don't know what it was but even though it had good power and acceleration it seemed like it vibrated a lot more than I thought it would and sounded sort of "pingy"?

I then reduced the top rpm to 12500. Still ran OK and sounded better no pingyness. I worked thru another half dozen cookies turned it off and pulled the plug. It was a dark steel grey - I haven't seen anything like that before. On my other saws I usually I see a spectrum of colors from cocoa brown, dark tan, beige, very pale brown and white or pale grey, and tune to get somwhere between a cocoa brown and dark tan.

I'm using Premium Gas with 40:1 Stihl lube oil.
Anyone have any ideas?

outdoortype · Nov 23, 2008

blsnelling said:
You're probably looking at the wrong area of the plug. The color that really matters is down at the base of the porcelan where it's difficult to see. Also, it's of no value unless it been running WOT in the cut and shut off without any idle time. Set it with a tach and leave it unless it's a modded saw.

Good point. I've noticed the service manuals instruct people to use a tach and make no mention of plug color. Also, I've heard from several others on this site that newer saws often display a leaner plug color than the older ones. FWIW, I've nearly went crazy trying to adjust by plug color alone. The tach and the plug color don't always agree.

ericjeeper · Nov 23, 2008

I prefer to read a used plug

A brand new plug may not have anything for the "Color" to adhere to. Besides a saw only has a brand new plug in it for the first run. After that it is always a "Used plug" I always try to achieve a 3 year old well worn Carhart tan.
But as previously stated. To read the plug the saw must be ran at wide open throttle in a cut, Then the kill switch hit while still at wot. Cause if you let it return to idle you will be technically reading the idle jets/bottom speed settings.

Brian S · Nov 23, 2008

volks-man said:
would that be the cs440? that saw is the reason i bought a tach. after a muff mod it wasn't any easier.

Ding ding ding ding! Yes, I cannot detect the diff between two and four stroking on the 440. It is set way rich right now for safetys sake, has good power in the cut but the plug is charcoal black and it smokes a little.

I'm trying to decide which tach to get, Baileys has a sen-dec with a sealed battery for about $67 and Amicks has one that runs on 9V for $85. I'm leaning toward the Amicks one.

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