Topic: Which Spark plugs in your 750 .

[754]

I think they used to take maybe d8es.. iirc.
 But over the last decade, when I try to get plugs I never find those, the pug is close but different letter designations then I wonder if it's the best choice.
 I prefer NGK.. which are you using ?

[Medyo Bastos]

d8ea, but I run champions


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[seanbarney41]

d8ea, but I run champions


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so, basically you don't ride your bikes?

[PeWe]

I have used NGK most of the time, D8EA.
Changed plugs a few days ago, now Denso X24ES-U. The engine feels to run smoother now, and slightly cooler too. I have not proved this by changing back to the old NGK D8EA that had only 2500 km.

Oil temp in oil tank could rather easy enter 248F (120C) when amb temp was around 27C and up. With Denso and amb temp 32-34C and twisting throttle more than before including a small twisty country road on 3:rd gear 4000-8000rpm with much pumping throttle. Max 118C in tank once but I really worked for making it hot. I guess oil temp will enter 115C instead of earlier 120C.
Plugs gapped 0.7mm (0.276").

[dave500]

d8ea, but I run champions


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so, basically you don't ride your bikes?

champions only come in lawn mowers these days?word is they gonna change the name to losers?

[brewsky]

I was cluelessly unaware I was using 3 D8EA's and 1 DR8ES-L
…..probably since the last valve adjust, and they all looked the same on the inside!
I think the DR8ES-L was spec'd for the Canadian models.....maybe?

OK....digging deeper into the service manuals reveals:

69-75....D8ES
76&77...D8ES-L, X24ES (Canadian uses resistor versions)
78...…...D8EA, X24ES-U (Canadian uses resistor versions)

[PeWe]

DR8ES-L was common here in Sweden in the 80's. My K6 have used them too.

[evinrude7]

d8ea, but I run champions


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so, basically you don't ride your bikes?

i'm fairly sure that's why my truck runs like #$%*.  i've been using champions for the last 4-5 years, replacing them every year. 

[seanbarney41]

d8ea, but I run champions


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so, basically you don't ride your bikes?

i'm fairly sure that's why my truck runs like #$%*.  i've been using champions for the last 4-5 years, replacing them every year.

yeah, everytime I pick up a non-running sohc4 and it fails to start, just pull the plugs and replace the champions with NGK lol

[Johnie]

100% NGK D8EA in each CB750K. Never had any issues. That being said, here is a 2010 post from Hondaman:

The D8ES was a "Super-wide heat range" sparkplug. The EPA made NGK discontinue these in the early 1990s. Their replacement was the D8EA, a colder plug by about 1/4 heat range step.

The D8ES-L (now defunct, except in the resistor version DR8ES-L) has a Longer tip (i.e., Extended Tip) to help burn off deposits.

The superior plug is the Nippon Denso X24ES-U, which is a little hotter than the D8EA and idea for the CB750, especially with alcohol-laced fuels. It has an even more extended tip, with a smaller ceramic nose, which was designed expressly for the CB750, circa 1974.

[Medyo Bastos]

d8ea, but I run champions


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so, basically you don't ride your bikes?

i'm fairly sure that's why my truck runs like #$%*.  i've been using champions for the last 4-5 years, replacing them every year.

yeah, everytime I pick up a non-running sohc4 and it fails to start, just pull the plugs and replace the champions with NGK lol

And I do the exact opposite.


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[PeWe]

100% NGK D8EA in each CB750K. Never had any issues. That being said, here is a 2010 post from Hondaman:

The D8ES was a "Super-wide heat range" sparkplug. The EPA made NGK discontinue these in the early 1990s. Their replacement was the D8EA, a colder plug by about 1/4 heat range step.

The D8ES-L (now defunct, except in the resistor version DR8ES-L) has a Longer tip (i.e., Extended Tip) to help burn off deposits.

The superior plug is the Nippon Denso X24ES-U, which is a little hotter than the D8EA and idea for the CB750, especially with alcohol-laced fuels. It has an even more extended tip, with a smaller ceramic nose, which was designed expressly for the CB750, circa 1974.

I have read that post too, plus other threads where Hondaman explains the differences and why's.

That's why I have 5 boxes of Denso and only 2 boxes of NGK plus some stray plugs of both, ordered from UK for almost 1/3 of the price compared with here before Brexit.  I have also some boxes of almost new plugs, used during carb tuning. I'll clean them for my K2 project and its tune. I doubt the plugs used whith floading floats can be cleaned
Denso box need more space.
EDIT: Forgot sideview. Both straps have same lenght. NGK has fatter isolator than Denso. That's why Denso is slightly warmer?

[Yoshimatic]

I use the NGK DR8EIX Iridium plugs and can’t fault them.

[Erny]

PeWe - not sure what's your conclusion - are those Denso better than NGK?
Just to know which I should buy for next replacement.

[PeWe]

PeWe - not sure what's your conclusion - are those Denso better than NGK?
Just to know which I should buy for next replacement.

I do not know which is the best since I do not have long riding time with the Denso after my carbs finally are correctly jetted.
Denso might be better for now. But they must work for a longer period of time too.

Very important that carbs are correctly jetted and ignition is correct too.
I suggest to buy both NGK and Denso to test.

I tried Iridium plugs before, NGK D8EA worked better but carbs were not correct them, pilots too lean and needles too rich which I fixed later.
I have set of each NGK DR8EIX and Denso IX24 Iridium. I do not know what they will do better. Maybe something when racing? I have not time to test them now, I need to see if the Denso X24ES-U sitting in now will work fine for next 10.000 km. This means this summer and next and maybe a step into another summer

But when thinking about them, I might try iridium for a quick check during a weekend. If they will make bike to run better and cooler, the multiple price (x5) might be worth it.
Then next... DENSO IX24 or NGK DR8EIX

Maybe someone has tested them both and can compare them with std plugs?

[Duke McDukiedook]

Denso X24ES-U here.

[flybox1]

DR8ES-L

[PeWe]

If getting different results, ignition system might different plugs to be the favourite.
My bike has TEC points, Hondaman ign module, NGK 5kohm caps and Dynatek 5 ohm coils. (spriral wound HT leads)

These coils have ONE fat weakness, the auto type connection where the HT wire is just plugged in. This can rather easy creep out. Enough if washing and spray with rather high pressure on the valve cover and a lead might pop out  just a little, holds in place by the rubber hose. I fixed that today again again. The problem can be occasional pops and bad behaviour that can be interpreted as too rich if not having this issue before.
I strapped all 4 wires to the frame close to the coils an hour ago. I hope they will sit where they should this time. Very irritating.

I'll create something better on my slow ongoing k2 build that have same ignition, TEC points, Hondaman ign module, NGK 5kohm caps and Dynatek 5 ohm coils. The coils must get something that can lock the leads in place. The rubber hose that seals might pull cable out from the coil too, if pressed in too hard...

[Stev-o]

NGK here too, about $2.50 at my local Autozone.

But have been tempted to try the ND's...

[kmb69]

Denso X24ES-U here too.
$1.91 at https://www.sparkplugs.com/product.aspx?zpid=10730
Even cheaper at other outlets.

[flybox1]

Mine ran poorly with the Denso.  Switched to the Dr8es-l's and my engine was veerrrry happy.

[DV Red Herring]

DR8ES-L. I use the resistor plugs because of my non-stock ignition system to introduce resistance. They run clean and strong.

[madmtnmotors]

Denso X24ES-U, Dyna S, Dyna 3-ohm coils, Dyna wires. No complaints.

[PeWe]

I have done around 800km the last week with Denso plugs. Carb tuning has shown a clearer face now. It runs smoother, but pilot is leaner at the same time it runs better. I need to increase one step on pilot jet since I increased fuel screws from 1 1/2 turn out to 2 1/2 which improved but still some occasional sneezing at low lifts.
Engine runs better than ever. I can cruise on 5:th gear,  2500 rpm and twist the throttle without any jerky hesitations.

My result is that Denso clearly need richer pilot circuit than NGK D8EA at the same time it runs better. There are different combinations, therefore different experiences of plugs...?
I do not use stock carbs, Mikuni TMR flatslides that were not perfectly jetted on the pilot side, needles and mains verified on dyno last year with NGK.