Author Topic: CB750 spark plug confusion (Read 31781 times)

sangyo soichiro · « **on:** May 18, 2009, 10:43:16 AM »

I am a bit confused. Sure, I could Google (and probably will), but I trust you guys more than Google. Also, keep in mind that I'm still a bit new to the CB750.

The owners manual suggests, for the CB750, to use the plugs
NGK D8ES(L) or
DENSO X-24ES

The Clymer's manual also suggests that these would work:
Champion A8Y-MC,
Bosch X300T@, or
Autolite HG1.

So far so good, right? Wrong!
I have two CB750's and a spare engine, so three engines in total. Pulling the plugs from these three engines, I see that they have,
Engine #1: NGK DR8EA,
Engine #2: NGK D8EA, and
Engine #3: Champion RA8Y.

So it looks like none of my engines had the plugs specified by the owner's manual or the Clymer's book.

So my questions are:
What do you personally use in your CB750?
What do all those numbers mean in the designation of the plug (e.g., what's the difference between NGK D8ES(L), NGK DR8EA, and NGK D8EA, etc.)?

mystic_1 · « **Reply #1 on:** May 18, 2009, 10:49:58 AM »

The 8s you are seeing in the numbers are the heat range. Lower number = hotter plug. You can use 7s and 8s in a CB.

DR8EA is a Resistor plug, don't use those because your plug caps have resistance built into them already.

I think the D8ES is the replacement for the D8EA, or maybe the other way around, but I'm not sure about that?

mystic_1

Duke McDukiedook · « **Reply #2 on:** May 18, 2009, 10:59:18 AM »

Go with the Denso, much better plug.

MCRider · « **Reply #3 on:** May 18, 2009, 12:56:26 PM »

Quote from: mystic_1 on May 18, 2009, 10:49:58 AM

The 8s you are seeing in the numbers are the heat range. Lower number = hotter plug. You can use 7s and 8s in a CB.

DR8EA is a Resistor plug, don't use those because your plug caps have resistance built into them already.

I think the D8ES is the replacement for the D8EA, or maybe the other way around, but I'm not sure about that?

mystic_1

Yup, the A replaces the S and refers to the shape of the electrode. The A is an improvement, S is discontinued.

Less important, the (L) taken from the old plug is a half step heat range. Also discontinued I think.

CBNJ74 · « **Reply #4 on:** May 31, 2013, 06:07:16 AM »

Bringing this one back from the dead.

Silly question to some but I'm constantly learning here. Do these plugs come pre-gapped?

ekpent · « **Reply #5 on:** May 31, 2013, 06:27:19 AM »

They are usually really close but it just takes a second to confirm with a feeler guage.

Xnavylfr · « **Reply #6 on:** May 31, 2013, 06:33:04 AM »

PRE-GAPPED???
They usually are BUT because the way they are boxed with a sleeve around the threads and electrode , it COULD still allow the electrode to hit something and bend it!! Takes just a second to check gap and good insurance that YOU know it's correct!!!

Xnavylfr(CHUCK)

MCRider · « **Reply #7 on:** May 31, 2013, 08:52:05 AM »

Agreed, they usually are and pretty close to 25thou. But with some ignitions and other set ups, one might wish they were 32thou, or something else. So SOP is to check them.

Xcmandan · « **Reply #8 on:** February 28, 2017, 10:55:54 PM »

Quote from: mystic_1 on May 18, 2009, 10:49:58 AM

The 8s you are seeing in the numbers are the heat range. Lower number = hotter plug. You can use 7s and 8s in a CB.

DR8EA is a Resistor plug, don't use those because your plug caps have resistance built into them already.

I think the D8ES is the replacement for the D8EA, or maybe the other way around, but I'm not sure about that?

mystic_1

Is it bad to use the resistor plugs though?

?

Sent from my SM-G900V using Tapatalk

ekpent · « **Reply #9 on:** February 28, 2017, 11:10:48 PM »

Stock plug caps have a built in resistor so if you use a resistor plug you are increasing that variable. Good idea to test old plug caps to see what condition they are in. I get D8ea for 750's at Advance Auto cheap with my online discount and pick-up at store.

flybox1 · « **Reply #10 on:** March 01, 2017, 07:08:36 AM »

NGK D8ES(L) - Love these. Always clean.
DENSO X-24ES - Hated these. Hard starts, not a clean burn.

PeWe · « **Reply #11 on:** March 02, 2017, 03:23:40 AM »

My bike like all these if I remember correctly
D8ES (this 79 early 80's)
D8ES-L

Especially these wich I also have tried the last 2 years ( + end of 80's and earlier)
DR8ES-L
D8EA

Hondaman explain some about the plugs http://forums.sohc4.net/index.php/topic,77832.msg869100.html#msg869100

If you need a plug that will work with 100%, buy NGK D8EA and available almost everywhere they sell plugs.

Racers running very hard talk about irridium plugs.
My bike did not like it since it behaved lik a 1 step cooler than D8EA on my street bike, tried the DENSO plug recommended for CB750.

DaveBarbier · « **Reply #12 on:** March 02, 2017, 04:58:11 AM »

This post was from 2009? That feels so long ago now

Deltarider · « **Reply #13 on:** March 02, 2017, 05:01:54 AM »

Really... oh dear... I must have dozed off I'm afraid... oh dear..

ekpent · « **Reply #14 on:** March 02, 2017, 05:19:16 AM »

At least someone worked around the "Search Function".

flybox1 · « **Reply #15 on:** March 02, 2017, 06:31:10 AM »

Quote from: ekpent on March 02, 2017, 05:19:16 AM

At least someone worked around the "Search Function".

Noobies

Stev-o · « **Reply #16 on:** March 02, 2017, 06:51:33 AM »

I'm still confused?

Deltarider · « **Reply #17 on:** March 02, 2017, 06:58:50 AM »

All models SOHC Four do well with the NGK D8ES-L. No exception. If the D8EA is identical (I don't know), so much the better.

flybox1 · « **Reply #18 on:** March 02, 2017, 07:47:04 AM »

NGK Alphanumeric spark plug code
The 'L' in the D8ES-L is for a specific electrode length (into the combustion chamber)

https://www.ngk.de/fileadmin/Dokumente/EN/downloads_not_used_in_download_area/ngk_zuendkerzen_code_en.pdf

jaka · « **Reply #19 on:** May 30, 2020, 02:23:29 PM »

Hi!
Strange! The swedish manual (translated directly from the american original) for the K1 and K2 models (same engine as the 1969 CB 750) states that NGK D-8ES L is the standard plug for the Honda CB 750 K1 and K2 models, but at the same time says that NGK D-8ES L should only be used for running in the first 300 km or during winter months. During summer and for faster rides NGK 10 E should be used.
So what is the "best" spark plug for general use on the 1969 Honda CB 750 during summer?

ekpent · « **Reply #20 on:** May 30, 2020, 04:44:41 PM »

Here in the States I would pop in the D8ea. PeWe is in this thread up a little and is from Sweden also. You should PM him.

News:

Author Topic: CB750 spark plug confusion (Read 31781 times)