Spark plug reading question.

[crazycalvin]

I now have about 100 miles on my new BB/Stage 2 job.  The build details are as follows:  Jugs bored to match 10.25:1 Cast S.E. pistons, S.E. 203 cams, S.E. MLS Head Gaskets, V&H B.S.S. on a Deuce.  I flashed the ECM with 141NU002 via a S.E.S.T.  I pulled the plugs and I thought they looked pretty good.  The front plug looks a little leaner to me than the back plug.  The front is not white, but on it's way to being "dust" or "cigarette ash" grey.  The back is on it's way to being a light tan.  For the most part, the RPM's where varied from 2000 to 4000.  I did twist the wick in first and second gear from 2000 to 5000 RPM's once at the end of my hundred miles.  This thing was very quick in comparison to when it was 88 w/ stock cams.  So the question is what does everyone think about my plug color description?  Thanks, Calvin.

[crazycalvin]

After reading my F.S.M. I see that my plugs are probably displaying a balanced combustion process.  It claims white and tan are okay.  I just thought white was too lean.  Thanks, Calvin.

[FLTRI]

Crazy,
Unfortunately, since the advent of unleaded fuels we are now using, the old method of reading plugs (tan color) doesn't work. That said, there is a way to effectively read and evaluate the plugs, but you must have a high quality plug scope or doctor's ear scope. Then you must be able to see the very bottom of the porcelain. The bottom should have a very thin ring of color, tan-to-ash.
The rest of the porcelain should look white or just a wee bit off-white.

That said, you must realize the reading you will get on the majority of porcelain will be based on the last AFR the engine saw.
In other words, if you want to tell if WOT AFR is good you must run the engine for sometime @ WOT (not reccommended on the street) and get what is called a "clean cut" which means, while @ WOT the ignition is cut, the clutch pulling and coast or brake to a stop. Then remove the plugs and take readings.

This method can be used for all TPs as long as you get a clean cut and take a reading from each TP used.

As you can see, this can be a real PITA and is not reccommend to be done on the street by anyone (except those who do it  ) due to safety concerns.
All I can reccommend is if you really want to know the actual state of your tune (AFR and power output) get to a competent tuner with the proper equipment.
Happy Holidays,
Bob
PS - All bets are off if readings are taken after idle, especially when restarted, due to enrichment occurring each time the engine is started/restarted.

[crazycalvin]

Thanks for the reply Bob.  I am not sure who I am going to get to tune my bike.  There are only a hand full of people that I would trust to tune my bike and none of them are close by.  I am planning on hooking up my SEST in record mode and doing some data runs and see if the knock sensor kicks in more than a few degrees of retard and see where it happens, if it does happen.  I just finished my big bore / cams upgrade and am pleased with the way the bike runs so far.  It pulls very evenly and nicely from 2000 to 5500 RPM under WOT in first and second gear.  It doesn't surge or exhibit any bad manners.  The gas mileage during the first 100 miles seem as good as it was before and that was varying the RPM's from 2000 to 3500 RPM's constantly in third, fourth, and fifth gears - up hill, down hill, and flat land.  The 2K to 5.5K blast came at the end of the ride and I was very surprised at how quick it was in comparison to 88 CID and stock cams.  Thanks again, Calvin.