Corrected Spark Plug "BASE" Reading

As some of you know, I have been going after the ultimate jet setting in my CR Specials and came across this... Thanks to Larry C!

www.angelfire.com/fl4/pontiacdude428/Readplugs.html

Note, the color plug chart provided was pretty good but there is more to reading plugs correctly then I thought!

* "Ground Strap" = Heat Range
* "Plug's Base Ring" = Jetting
* "Porcelain" = signs of pre-ignition/detonation

As can be reviewed in the top right image (exactly like mine) where I was believing a was fairly well dialed in.... Well wrong of course.... :blush:

Only to realize I'm still burning a tad rich in my jet configuration.... Now for the most part this would be just fine, especially on a new engine build where I'd prefer to be on the rich side especially here in AZ. Since I'm now fully broken in @ 2000 miles, time to tweak her even further...

Henceforth, change to YY9 needle set at clip position 4.
I have no hesitation, lul, flat spots nor back fire/popping during acceleration or deceleration but my plug colors (top right image) now informs me it's not 100% yet... Notice I said YET! :laugh:

New plugs in and I'll keep an eye on them and will provide pre & post images of the results. If still a tad rich, then drop to clip position 3 to lean her out even further...

Now on to perfection.... then get her re-Dyno for Torque & HP ...

As previously disclosed, I dropped down 2 on the main and 3 down on the slow jets so good there. I mostly ride mid range 4000-6500rpm so needle it is... About the only thing left damn it... :laugh:

I'll keep you all posted with images soon...

EDIT: For those who may be interested for print out, I inserted into doc and pdf formats...

PDF: In file data base...
kzrider.com/index.php?option=com_docman&...d&gid=460&Itemid=108

Doc: Attached...
EDIT: Not allowing doc attachment for some reason...


OMR

In case anyone needs for CR Specials...

Word Doc attach....
Trying again to attach doc format...

Nope, won't go for it..... :laugh:
Ah well use the pdf in the file data base setion....

I wonder about the relationship between the air/fuel mixture, the spark plug heat range, and the temperature at which an engine runs. My KZ650C1 originally came with rather cold plugs as was recommended in the first edition of the factory service manual. These plugs always appeared to show the engine running rich because they had the dark, sooty look. Since my bike was completely stock, I resisted the temptation of fiddling with the carb jetting and simply accepted this condition for years. Eventually I bought a newer factory service manual for the same bike and was surprised to see that Ma Kaw had changed her plug recommendation to a hotter plug. I began using the hotter plugs and the soot disappeared. I suspect the first recommendation was based on Kawasaki engineers running the bike extremely hard on a Kawasaki test track thus no soot.

Here’s my issue. If I had fiddled with the jetting to make the bike run more lean and hotter I probably could have made the original cold plugs run cleaner but the engine may have been running overly hot. By switching to the hotter plugs, the plug runs hotter because of the different insulator length, but the engine itself runs at the same temperature because the air/fuel mixture didn’t change. So it seem to me when someone is building or modifying an engine the plug itself is only one indicator of the correctness of the carb jetting. As was pointed out, dyno time would seem to be important as well as measuring the temperature of the engine, head, etc. Otherwise too hot a plug could appear perfect even though the engine was running rich, or too cold a plug could appear perfect even though the engine was running lean and too hot. Thoughts?

I queried into this with Plummen, Larry C and Buzz @ Dynoman... None of which recommended the hotter/colder plug concept.... Even the OEM service manual places caution in this matter....

The attached images below are of the previous YY8 plug conditions on clip position 3.

As can be reviewed, the base rings depict a tad too carbon still... The ground strap is ~ correct where the banding is close to the middle so close to being correct. The porcelain is a white/tan in color. These plugs have ~ 500 miles on them.



I installed the YY9 needles with clip position on 4 last night and as mentioned, installed new plugs. Took her for a 10 mile run and shut her down... Slight full turn discoloration on the base ring but still to early to tell yet... Didn't feel any lulls, accelerated nicely, pulled strong low to mid range with no popping exhaust on deceleration or engine knocks.

I'll get some more miles on these plugs and see where she stands. If required, change to clip position 3, insert new plugs once again and run her....

I'll post images as we go...

OMR

dave,
i m a dumbass and know absolutely squat.....that being said,
sometimes you want to tune an engine with a little bit of insurance....a tad rich might not get you the high dyno numbers, but you will have an engine that will live a long time and get you respectable performance.....change the oil a little more often, and you will offset that tad rich condition.....if you tune a motor to the edge and something
goes a little off kilter, game over.....
i ve seen many a car forum where the a/f ratio was set for max dyno numbers and the timing is on the edge and poof....
i have a tuner for my merc and play the conservative game with my timing.....i would rather lose a couple of horse up top and know it will live to rev to redline another day...
just my .02.....its worth exactly what ya paid for it!!!(stolen line)......keith

note to mrs omr:hide daves tools so he'll quit tweaking on those poor carbs and spend more time riding that damn bike,some of us live in nebraska where it snows a lot and we dont getto ride in january! sincerely "the juan and only" ! :laugh:

"i m a dumbass and know absolutely squat.."... On the contrary, wise response...

And you are 100% correct where I as well would rather be slightly on the rich side versus lean... to a point though.... I'm running slightly more than a tad with the YY8 needles....

I'm pretty confident this will be the last I need in my jetting... Don't really care about total max HP I can possibly obtain... The Dyno will inform me of the Air Fuel Ratio settings as well....

Plummen... :laugh:

BTW all, this is what I started with...

Pre-Jetting:

Old Man Rock wrote:

Plummen... :laugh:

BTW all, this is what I started with...

Pre-Jetting:

dave,
if i remember right, the bike passed az emissions?

for comparison and critique.....they have been kicking around the bench for a month...they are not in cylinder order....remember, one of the valves had a seal go south..

Yes but I fibbed the idle test by tweaking the pilots way out lean...

If you'll remember the story, I couldn't idle it in the testing bay and they wouldn't let me tweak so I pushed out of the bay, tweaked the carb's richer a 1/4 turn or less and passed...

:laugh: :laugh:

Now look at your's versus mine.... there you go who;s on the rich side.... ME!!!! :laugh: