Spark plug color

Post by **Jdflyer** » Sun Sep 04, 2016 2:50 pm

So getting ready for Williams gathering and pulled the spark plugs to take a look. The plugs look like they are a lean, but the color tune is blue at both idle and 3000. Any opinions?

image.jpeg

cktrap · Post by **cktrap** » Sun Sep 04, 2016 4:20 pm

Looks lean to me.

keith0alan · Post by **keith0alan** » Sun Sep 04, 2016 4:28 pm

Are you getting any stumbles at cruise? If not it is fine.

david premo · Post by **david premo** » Sun Sep 04, 2016 9:36 pm

The plug looks fine, with the unleaded fuel we use now that is the correct color. When we had leaded fuel it would give you a brownish color to the plugs. Looks like a nice mixture, when it is lean the color is extremely white with tiny light black spots cause by the pre-ignition.

Dave

cktrap · Post by **cktrap** » Mon Sep 05, 2016 7:50 am

david premo wrote:The plug looks fine, with the unleaded fuel we use now that is the correct color. When we had leaded fuel it would give you a brownish color to the plugs. Looks like a nice mixture, when it is lean the color is extremely white with tiny light black spots cause by the pre-ignition.

Dave

I learn something new every day. I must be tuning mine a little rich.
Keith

Post by **Linda** » Mon Sep 05, 2016 9:55 am

Would be nice to see a pic of a lean plug for comparison.

Linda
Edit: Found a link:
http://www.verrill.com/moto/sellingguid ... rchart.htm

RBMann · Post by **RBMann** » Mon Sep 05, 2016 12:34 pm

I had a lumpy idle and found my main jets at different heights. Front two plugs were rich and the rear looked okay to a little lean. I had set them last year. Now something to watch in the future.

IMG_9118.jpg

msampsel · Post by **msampsel** » Mon Sep 05, 2016 7:14 pm

RBMann wrote:I had a lumpy idle and found my main jets at different heights. Front two plugs were rich and the rear looked okay to a little lean. I had set them last year. Now something to watch in the future.

IMG_9118.jpg

Were these plugs ever used? Look like they came right out of the box

Post by **C.Costine** » Mon Sep 05, 2016 7:34 pm

david premo wrote:The plug looks fine, with the unleaded fuel we use now that is the correct color. When we had leaded fuel it would give you a brownish color to the plugs. Looks like a nice mixture, when it is lean the color is extremely white with tiny light black spots cause by the pre-ignition.

Dave

Dave, are you sure about that? I have seen pics from some time ago of piston lands and heads very white from lead. Over the many years since lead went away I have seen lots of tan plugs.

RBMann · Post by **RBMann** » Mon Sep 05, 2016 9:30 pm

msampsel wrote:
RBMann wrote:I had a lumpy idle and found my main jets at different heights. Front two plugs were rich and the rear looked okay to a little lean. I had set them last year. Now something to watch in the future.

IMG_9118.jpg

Were these plugs ever used? Look like they came right out of the box

Yes, but lightly around 300-500 miles. Most were chasing Ted.

msampsel · Post by **msampsel** » Tue Oct 10, 2017 2:59 pm

Reviving this thread, here are some colors of plugs with 1100 miles. Used wideband to get to a 13.2 reading.
Interesting the "front plug" for each carb shows the most reddish tint.

Seems I needed to add 2 qts of oil too.
Some of it leaks from the rear seal. Oh well, acceleration is great, crisp no stumble. Cruise felt odd, not an obvious stumble, but maybe it was. Certainly happier engine when accelerating.

keith0alan · Post by **keith0alan** » Wed Oct 11, 2017 7:47 am

What is your gap set to and do you have an electronic dizzy? The gap needs to be set to about .040 with the electronic dizzy. A stumble at cruise is usually a lean miss. I have read that the random things they put into gas these days makes the colors of plugs harder to interpret.

Gregs672000 · Post by **Gregs672000** » Wed Oct 11, 2017 12:22 pm

Nothing wrong with the color on any of them it seems to me, but it is interesting that you're getting two different colors on plugs that are being fed by the same carb! Different valve lash?

AidanDawn2000 · Post by **AidanDawn2000** » Wed Oct 25, 2017 10:42 pm

Does anyone know anything about "glazing" on the plugs? it's hard to see in the pics but the plugs are strangely glossy and glazed looking. Also I'm getting dark on one side and lighter on the other

All the same plug

IMG_0705.JPG

IMG_0706.JPG

IMG_0707.JPG

IMG_0708.JPG

And yes I know there a little rich, I beefed things up on the way to Shasta to keep it from pinging and haven't gotten around to switching back.

MicVelo · Post by **MicVelo** » Thu Oct 26, 2017 10:00 am

Generally, glazing or glossy deposits on a plug mean overheating of the plug which could result from improper fuel mixture, a plug that's not in proper heat range, etc. Your plugs, though, look pretty normal other than the slightly over-rich condition you mentioned (which could be the cause of the glazing). Inconsistent wear/burn patterns are fairly normal and usually have to do with the configuration of your combustion chamber. Also not a big worry.

I'd just change 'em, correct the AFR, balance the carbs (last pic seems to show inconsistent grades of black) and monitor them from time to time.

Datsun Roadster Forum-311s.org

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