Honda-SOHC
SOHC.co.uk Forums => CB500/550 => Topic started by: deltarider on April 23, 2024, 02:58:47 PM
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Here is a question the experts in the international forum wouldn't (or couldn't?) answer.
In particular CB500/550s are known to easily foul their sparkplugs at idle. What - in theory - would make these CB Fours idle better: gapping the electrodes 0,6mm or 0,7mm? Please substantiate your answer.
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I dispute this,
My 500 has no issue
In fact, I use a harder plug than reccomended, an 8 instead of a 7 ,
I have checked the tickover mixture, and my airscrews are turned out more than normal,
I also have Boyer ignition, and run the plug gaps at 33thou,
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I dispute this,
My 500 has no issue
In fact, I use a harder plug than reccomended, an 8 instead of a 7 ,
I have checked the tickover mixture, and my airscrews are turned out more than normal,
I also have Boyer ignition, and run the plug gaps at 33thou,
Is that plug a D8ES, a D8ES-L or a D8EA? What is the position of your airscrews.
I myself have had D8ES-L plugs many times, recommended by mecs if you travelled at high speeds.
Nowadays - many years older - I run D7EA. I see no advantage in gaps over 0,7 mm. You can expect they will erode sooner.
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Actually, I run Denso x24ea-u
I believe that the are equivalent to the D 8ea
A d7ea is normal for the 500
The 8s are for 400,750 etc
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Originally in the book it was D7ES which wasn't a particular good plug. Dealers in Holland considered it OK for the break-in period, but advised later to use newcomer D8ES-L if you would ride the highways. The D8ES probably would have been to cold. You may say the D8ES-L with its tip that protruded just a tiny bit further, was in between the 7 and 8. Also Honda France advised them for the CB500/550 and called them auto-nettoyante (selfcleaning). BTW, the D8ES-L was/is used on a wide variety of bikes. I had them in my CB500 on all my travels in Europe, often at maintained high speeds. I wouldn't have felt comfortable with the 7, not when you, what happened more than once, were late to switch to reserve... So it depends on your riding, but if the D8EA is the new name for the D8ES-L, it's a good choice. If you don't cruise over 5000 rpm, you may consider the 7EA.
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Delta, i disagree,
On the asvise of an ngk rep who was a well respected sidcar racer i used D7EV in my 500 that went all over the UK and to the Isle of Man regularly plus commuting 7 miles to work.
Never fouled, never failed yes nearly twice the price but well worth it the =L was always sold as a "half grade"
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Delta, i disagree,
On the asvise of an ngk rep who was a well respected sidcar racer i used D7EV in my 500 that went all over the UK and to the Isle of Man regularly plus commuting 7 miles to work.
Never fouled, never failed yes nearly twice the price but well worth it the =L was always sold as a "half grade"
NGK came with the D8ES-L for a reason. Other plugs that had a less protruding electrode, fouled. That problem needed to be adressed. In my documents, the D8ES-L was characterised by NGK as "Special Design". Although it's been interpreted by forum members as "half grade" I've not seen this confirmed by NGK as such, nor by Honda. As the D8ES-L indeed fouled less, it could be used by CB500/550 owners that had read in their Owner's Manual and I quote: [...]" if the motorcycle is going to be operated for extended periods at extremely high speeds and near maximum power in hot climates, the spark plugs should be changed to a colder heat range number." That the American EPA was somehow involved in the birth of the D8ES-L, is a story that so far comes from one member only in the international forum. I have seen no confirmation of that story yet. I mean: how about all the other markets that didn't have an EPA?
Back in the day, every owner of a CB500/550 on the European continent ran the D8ES-L plug. My personal experience was that this plug fouled no more than the D7ES did.
One of the best manuals I have, is the French one that was established in close participation with Honda France. On page 83 we read:
Bougies
La CB 500 est équipée de NGK D-7 ES alors que le modèle actuel (CB 500 K1) possède des bougies NGK D-8 ES-L qui ont la particularité d'être autonettoyantes. Il est conseillé de monter également ces bougies sur la CB 500.
In translation:
The CB 500 is equipped with NGK D-7 ES while the current model (CB 500 K1) has NGK D-8 ES-L spark plugs which have the particularity of being self-cleaning. It is recommended to also fit these spark plugs on the CB 500.
And that's what most of us did.
I'm sorry I cannot comment on experiences/reviews which may be biased by free handouts. Untill I have more information, I consider them anecdotal.
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On my 500, I have D7EA and it ticks over perfectly, they do not foul. Good response in all rev ranges, hot and cold.
Perhaps you should look at ignition timing and carbs rather than plugs.
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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
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This is starting to read like "Plug-gate".
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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.
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Aha, that is valuable information. I had not seen this half-grade mentioned before. In Holland the general advice was to have the D8ES-L. Let me put it like this: if the D8ES-L fouled, than a "7" also did.
Now that we're older ;) and also have a lower national speed limit than back then, both the 7 and the D8ES-L can be used no prob.
I am curious if the D8EA is identical with the D8ES-L and if the D7EA also has a tip that protrudes just a fraction more than the D7ES. I have tried to see the difference myself, but I'm afraid the difference is minor and... older eyes don't help either. ;)
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Back in the 80s
I also used Champion A8Y
Definitely a projecting nose plug,
The bike ran well, but they became difficult to get
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Not owning a 500, I've not that specific experience to offer.
A big BUT though, genuinely I've never had problems with plug "fouling" on four stroke engines, that's across all bikes and cars I've looked after since early 1970s.
Another observation, the Boyer ignition is very, very competent in it's delivery. I've no problem working with the std system, believing it to be mechanically almost peerless in it's design, application and component specification .... the Boyer i can see by comparison does offer tangible benefits if that's chosen by the owner though.
Among those benefit appears the ability to fire more adverse mixture range more of the time with exceptional repeatability. This seems to support a more optimum idle mixture that may give benefit in any residual unburnt component/fuel that may be affecting the fouling determination this topic is about.
Very loosely, NGK plug heat range on these engines could be approximated to continuous load under wider throttle for extended periods of time.
A 7 giving ROUGHLY decent coverage for 7000 rpm running.
Likewise, an 8 for predominately covering an 8000 rpm consistent load type riding. Etc, etc
Basically its a balance of number of actuation per minute against heat clearance from the engine, ambient air temp also playing a part in air cooled motors too.
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I agree completely which is why I was asking if the fouling might have another cause, nothing to do with plugs.
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[...]
Another observation, the Boyer ignition is very, very competent in it's delivery. I've no problem working with the std system, believing it to be mechanically almost peerless in it's design, application and component specification .... the Boyer i can see by comparison does offer tangible benefits if that's chosen by the owner though.
Among those benefit appears the ability to fire more adverse mixture range more of the time with exceptional repeatability. This seems to support a more optimum idle mixture that may give benefit in any residual unburnt component/fuel that may be affecting the fouling determination this topic is about.
[...]
The advantage you attribute to B#B, is valid for any EI that has a transitor doing the switching. Realise that even in stock configuration, coils will be fully saturated. Only in border situations a transistor has the advantage of more reserve as there's no loss due to mechanical breakers (tiny sparks can be seen in stock set up). The steeper rise time a transistor ignition provides, will also offer some reserve in border situations. That's all to it, I'm afraid. There's no shortage of spark duration because @ idle initial peak voltage will be relatively low (estimation around 7kV). An EI will NOT give a higher voltage. Why should it, if the circumstances are thus, that already 7kV is enough to bridge the plug gap. Ergo: lots of energy available.
It's the gap that determines a higher or lower initial peak voltage and the atmospheric circumstances in the combustion chamber ofcourse.
In my personal situation, I'm experimenting (you guys know me ;)) by following what is advised in a American Honda booklet. Needles are now raised one notch (and thus in 4th) and the airscrews are two turns out.
Here is something I have never communicated before. In the very first year I owned my CB500 (1980), I travelled as far as Greece. On a camping in the Peloponnessus I decided to open the Haynes manual. Being completely ignorant I followed the data in forsaid manual and have set the airscrews at one turn out. To this day I wish I had never touched them. I should at least have made a note what they were in before. Immediately the next day I noticed a difference: a negative one and never thereafter in 44 years have I been able to regain that perfect utterly smoothly accelerating CB500 again. Don't take me wrong. It has always been good thereafter, but never so perfectly accelerating as before. Later the properties of gasolines changed which made it even more difficult. That's why I am always curious to know what position other CB500 owners have their airscrews in. If my plugs stay clean at idle, driveability in acceleration suffers. My understanding is that even 1/8 of a turn can make a big difference and at least one Honda mechanic has told me that the position of the airscrews of all 4 can individually differ in position more than just 1/4 of a turn. Soon I hope to use my restaurated CO gas analyzer and see what an initial 4% CO at idle will bring.
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You're making the assumption that I've said it needs more power (supplied by the Boyer ? ) which is not what I've stated.
I agree it doesn't, there's other attributes within that system that hold value in this performance arena.
Question .... can you describe the failure mode within the combustion chamber which gives erratic acceleration response as you've described it ? In other words, why are you not getting a perfectly linear response with the settings you have.
Honda never state (as far as I appreciate) that you have to use equal idle circuit settings, just a suggested start point, from which their setup routine .... well written in my view ..... will allow settings for individual cylinders in giving long term combustion equality. Thats just normal in my reading of their factory instructions. It goes further in the later PD carbs, such that it calls for correct settings, then to record those individual adjustment as the genuine reference point from then onwards.
Also it states that they are set in this way at factory, advises not to arbitrarily adjust them without making good record of their factory position BEFORE working on them.
Sensible, I feel.
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You're making the assumption that I've said it needs more power (supplied by the Boyer ? ) which is not what I've stated.
Sorry if I did. I may have been misled by what so many believe who attribute super powers to an EI. You have shown far more knowledge. The ignition in itself is quite an ordinary process. Complicated is that we deal with 1) an idle, 2) load (acceleration) and 3) cruise.
Question .... can you describe the failure mode within the combustion chamber which gives erratic acceleration response as you've described it ? In other words, why are you not getting a perfectly linear response with the settings you have.
I wouldn't call it erratic. Before I touched the airscrews in 1980, acceleration was just fabulous. In my memory I was constantly turning the throttle grip forward to prevent the bike from leaping like a jaguar. Later it was just good. The mec that initially has tuned my bike - either in Japan or in Holland - must have done a perfect job. Later a Honda mec - not the same - learned me that airscrew positions may need to differ further than just the +/- 1/8 of a turn Honda prescribes. BTW, in his years long experience the CB500 was the hardest to fine tune of all the CB Fours. This could relate to the special carburetor setting, models for the European continent had. I don't know. Not much later after my trip to Greece, gasoline quality changed dramatically. I remember having read an article by a widely respected professional writer for automotive and motorcycle mags - who himself owned a CB550K3 - in which article he concluded in his last line (in despair?) that "some motorcycles just don't like some gasolines". I have never asked him, but he himself may have been struggling with his CB550K3, after the arrival of the changed gasolines.
Honda never state (as far as I appreciate) that you have to use equal idle circuit settings, just a suggested start point, [...]
I didn't say Honda did, but Honda did give a range of +/- 1/8 of a turn. Some mechanics judged the difference in air screw position amongst the 4 could need to be more than that. I suppose they may have had a reason for that.
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Interesting thread. This fouling at idle - is this when the revs drop after running steadily for 20 seconds and can be cleared by revving the throttle to restablish the steady idle? Mine does have that tendency on the denso plugs but also one cylinder which is cooler than the others so I’m guessing that’s the one that fouls.
I have found on many different bikes cars lawnmowers-that iridium plugs give better starting, smoother idle and avoid fouling on two strokes. It seems there isn’t one available for the 550 - why not ?
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Interesting thread. This fouling at idle - is this when the revs drop after running steadily for 20 seconds and can be cleared by revving the throttle to restablish the steady idle? Mine does have that tendency on the denso plugs but also one cylinder which is cooler than the others so I’m guessing that’s the one that fouls.
I have found on many different bikes cars lawnmowers-that iridium plugs give better starting, smoother idle and avoid fouling on two strokes. It seems there isn’t one available for the 550 - why not ?
Think I'd initially swap the plug lead with it's paired one to see if the cool running transfers with that lead. If it stays where it was, then looking more at that cylinder condition, compression analysis to count that out, idle jet system to ascertain if there's any impairment.
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If there's response by swapping the leads over (within one oil pack) then analysis of why that could happen may give answer.
There's specific performance in the condenser relating to this (if the original system is in place) with it's ability to fire the mixture.
The opposite ends of the coil have slightly different spark characteristics, with also the condition in cylinder from the live one to the wasted spark one maybe causing a bias to disadvantage the live cylinder on compression and give a shift in performance to that cylinder.
Swapping the leads checks for that, also the insulation of the HT too.
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On second thoughts... I may have exagerated a bit. Fouling happens when there has been excessive idling: too many times for extended periods of time. I have made it a habit when bike idles too long, due to traffic, to rev briefly every minute or so. When idling for >15 minutes, without revving at least once, I can not expect plugs to stay deer brown.
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My understanding of spark plug technology is they are designed to be self cleaning at higher revs/temperatures - obviously there is a limit to this function so if the mixture is overly rich right through the range they will soot up.
I suspect throttle blipping was something we used to do to keep the plugs from sooting up at idle to make a clean getaway.
My experience primarily with cars using carbs is that a vehicle used for mostly short journey work fitted with the manufacturers standard plugs would foul up badly needing a good run to clear the carbon deposits.
I particularly remember a disabled customer who ran an Automatic Opel Commodore 2.5 GS (1974) from his home to work a distance of less than a mile. On collecting his Opel from Ashbourne it would not exceeed 45-50 mph flat out. During the course of the journey to our service department in Burton the top speed would slowly improve until it would reach 60-65 mph. After a service the car would drive like it should for a 2.5 litre straight six.
Fitting a different plug type to cope with the short journey used mostly on auto choke was not an option as the customer would drive to Scotland a few times a year where he had family. In reality he wouid have been better driving a car with a much smaller engine.
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Unfortunately I haven't been riding like in the past: looooong stretches >130km/h uninterupted on motorways. It was always great how well the engine responded afterwards.
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Could I suggest something I do,
Take the bike for a run about 15 to 20 miles get it nice and warm
When home, keep the engine running, put on centre stand
Get your long screw driver
Now ,turn one airscrew a quarter turn out,
Check what happens, blip the throttle, OK?
If it struggles,turn to previous settings
But if its OK,do another, repeat, and check
Remember, Modern fuel is different than 50years ago,
It might like a leaner tickover
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I'll put it out there, plug fouling can also be caused by oil burning.
Worn rings or valve stem seals/ guide wear.
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It's not oil. I smell petrol so it's overrich. Fuel is different these days. Maybe Shell is right and you can adjust to leaner and save fuel when you run their V-power, which I do. The problem with these bikes is, they will always run and keep going where a twin simply quits rightaway when something is not in good order.
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Is it possible that you smell unburnt petrol as the oil has fouled up the plugs first - cause oil deposits on the plugs leading to unburnt petrol afterwards. Often you can see no blue smoke in oil burners.
Where rings have been replaced rather than a rebore with some glaze breaking I suspect some running in might be needed before worring about plug colours.
As an aside my 400 that was rebored by Graham has only covered some 230 odd miles - unless it starts misfiring I will not check the plug colours until it has covered about 600 miles. My idle speed is good and even - to date only bench synched the carbs as it's now running so well after my initial mistake on the plug connections when it was a two cylinder bike for a while!
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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.
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If there's response by swapping the leads over (within one oil pack) then analysis of why that could happen may give answer.
There's specific performance in the condenser relating to this (if the original system is in place) with it's ability to fire the mixture.
The opposite ends of the coil have slightly different spark characteristics, with also the condition in cylinder from the live one to the wasted spark one maybe causing a bias to disadvantage the live cylinder on compression and give a shift in performance to that cylinder.
Swapping the leads checks for that, also the insulation of the HT too.
Thanks. the leads on my bike are very stiff. I’ve remade the cap connections but I’m not very happy with them. Definitely thinking of doing the Ash fix. On the other hand it starts well and has no high Rev mis fires which makes me think ignition is ok. I can live with the slight tendency to idle foul and my air screws are out more than 1.5 turns from memory running on shell e5. I’ve improved no 1 cylinder running cool by installing #35 pilot jet and overall the bike runs very well.
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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.
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Why not? If you can design for whole numbers you can design for half way
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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.
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Using the 8-L would make them even more prone to fouling at tickover and low load,
Must be for high load ,like racing
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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 ?
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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.