Plugs fouling at idle

[deltarider]

The fact that the L was a half grade came from the same reptat suggested d7ev to me, and that man knew how to read plugs

Thats noted on some published charts too .... the -L designation.

https://www.ngk.com/ngk-spark-plug-numbering-systems this lists that design element, although note that they have a statement of NOT being NGK USA official scource.

The listed data looks comprehensive though.

Compare the above to what they gave me as answer, after I took the effort to contact them.
My question was:
      Dear Cust,
Here's a question owners of motorcycles that had the NGK D8ES-L sparkplug prescribed, never had answered:
                 Is the  D8EA plug, as far as heat range, the same as its predecessor D8ES-L?
In addition: 
                 Is the D7EA plug just a renamed D7ES, or does the  -A suffix ('Special Design') imply the D7ES was indeed modified?
Core of our uncertainty is, that we have no clue what the meaning of 'Special Design' is.
We realise it may be difficult for you to find the answer. You may have to consult older employees who can remember. Somebody must know.
The issue has been debated over and over in various fora around the world (Germany, Holland, France, UK and US) and no NGK chart ever solved the uncertainty. https://www.ngk.com/ngk-spark-plug-numbering-systems

And here the answer:
     Hello,
Thank you for contacting us! D8EA had a heat range of 8 and D8ES-L  heat range 8.5. The (L) stands for Half Heat Range.
As a Distributor for NGK the  -A suffix ('Special Design') is still a mystery to us. You will have to contact NGK directly at 1-877-473-6767 ext #1 or www.ngksparkplugs.com they may have more details on this.

Personally I find it hard to believe that the D8ES-L has heat range 8.5.
Your comments please.

[Bryanj]

Why not? If you can design for whole numbers you can design for half way

[deltarider]

Why not? If you can design for whole numbers you can design for half way

In my understanding most of us took the D8ES-L heat range for in between 7 and 8.

[Johnwebley]

Using the 8-L would make them even more prone to fouling at tickover and low load,

Must be for high load ,like racing

Sent from my SM-A546E using Tapatalk

[K2-K6]

Why not? If you can design for whole numbers you can design for half way

In my understanding most of us took the D8ES-L heat range for in between 7 and 8.

Thats my view of extending the central electrode out into the combustion chamber too. It would allow it to heat more than a straight 8 to raise potential tip temperature, but not as much or as far as a 7 ..... well that's how I visualise it, whether that's true or not.

Any arrangement with longer route from porcelain at tip into the surrounding structure SHOULD  make the tip retain more temperature  .... that's generally what plug design achieves.

Wouldn't an 8.5 be called a "9-L" by that description  ?

[K2-K6]

For me the question is formost: can I indeed compensate the needles clip in 4th groove by adjusting the air screws to two turns out, like that American Honda specifications booklet suggests or should i return to the European set up with needles clip in 3rd? I have always had my doubts about that US booklet and I therefore volonteered to experiment.

They are going to compensate in different ways, although overlapping in their effect, the two changes that is.

Lifting the needle iis going to give a response in fuelling curve in roughly a parabolic curve being nil or low change at closed throttle slide ... also nil at full open, with increase in fuel through that curve region.
Essentially raising the equalised air fuel ratio throughout the mid range of slide position by placing the needle higher in that air controlled slide movement.

The change in idle jet circuit will not shift the maximum flow without change to the jet number .... but will give less fuel at idle by opening the air inlet via the screw .... then reach maximum flow for that circuit (conditional on that jet number) further up in the vacuum range of venturi flow.
Longer "slope" response from idle circuit, meaning it doesn't ramp up /accumulate fuel increase in quite such an steep response as having the screw further inwards.
This may give you flat spot just off idle when lifting the throttle initially, it can also give problems at idle in consistency as it requires the slides to be set lower on "master" rpm screw, making it potentially out of range in vacuum specifications listed in carb balance.  Sometimes this affects throttle response in rolling the power on and off as the vacuum gets too high with closed throttle when closed with revs higher .... feels a little "sticky" and non linear with more severe engine braking affect on closed throttle.