Honda-SOHC

SOHC.co.uk Forums => CB500/550 => Topic started by: florence on April 19, 2019, 04:20:12 PM

Title: Spark plugs
Post by: florence on April 19, 2019, 04:20:12 PM
I'm just about to replace my plugs.  Currently has worn out DR7ES but looking at manual it say D7ES.  Does anyone know aht is correct and best place to buy them.  I have aftermarket air filters and laser 4-1 exhaust if that infleunces decision. 1974 CB500/4
Title: Re: Spark plugs
Post by: Nurse Julie on April 19, 2019, 04:34:33 PM
DR denotes the plugs are fitted with resistors. Only fit DR tyre if your plug caps are not resisted. D7EA are non resisted, so you need resisted plug caps fitted. You shouldn't use both resisted caps and plugs together, just one or the other.
Title: Re: Spark plugs
Post by: florence on April 19, 2019, 04:59:22 PM
Hey thanks, I did not know that.  Gosh, I think the caps I have are resistor (NGK) so looks like I should get D7ES.  THanks again,
Title: Re: Spark plugs
Post by: Brian. on April 19, 2019, 05:37:41 PM
Hello Florence,

I bought my plugs a couple of weeks ago, and a set of plug caps, from here:- https://www.gsparkplug.com/

It was the best deal I could find, and they came in a couple of days.

I can definitely second Nurse Julie's comment above regarding not using resistor plugs and resistor plug caps together, it was one of the reasons why my CB550 ran so badly when I bought it.

What probably made mine worse still was that the resistance of the plug caps when checked on a multimeter (if you have access to one) was very high, they should be 5k ohms; two of mine were about 9k ohms and the other was 13.  It's a wonder really that there was any spark at all I guess.

New D7ES plugs and new caps, less than £20 all in, and ignition problems all sorted.

I hope this helps!

Brian.
Title: Re: Spark plugs
Post by: florence on April 19, 2019, 07:15:27 PM
wow Brian, great site, shall order today.  My ignition has been a bit unreliable lately, no.3 keeps cutting out.  Replaced coils which were always bad in the wet.  Now with these plugs should all be good.  Thanks to both of you for great advice.

Steve
Title: Re: Spark plugs
Post by: SteveD CB500K0 on April 19, 2019, 07:34:48 PM
Of course, resistor plugs/caps were required in the 70s because the ignition systems broadcasted in the FM frequency band (98-108 MHz).

Nowadays nobody broadcasts there (not that we care about anyway)

Our bikes would have to be nuclear powered to interfere with DAB or 3G/4G bands


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Title: Re: Spark plugs
Post by: Brian. on April 19, 2019, 07:53:33 PM
wow Brian, great site, shall order today.  My ignition has been a bit unreliable lately, no.3 keeps cutting out.  Replaced coils which were always bad in the wet.  Now with these plugs should all be good.  Thanks to both of you for great advice.

Steve
OK Steve, well, if it's any help, the plug caps I ordered for mine were described on the website as 2no "VD05F black (8052)" and 2no "XD05F black (8072)" and they are a straight swap for the knackered ones that were fitted to me bike when I bought it if that's any help.  Please do check for yourself that they are right for you though, before you part with your money!

Those and four plugs plus P&P and VAT came to £19.46 total.  Which I thought was more than OK to be honest.

Hope this helps!

Brian.
Title: Re: Spark plugs
Post by: Johnwebley on April 19, 2019, 08:27:54 PM
Hello Florence,

I bought my plugs a couple of weeks ago, and a set of plug caps, from here:- https://www.gsparkplug.com/

It was the best deal I could find, and they came in a couple of days.

I can definitely second Nurse Julie's comment above regarding not using resistor plugs and resistor plug caps together, it was one of the reasons why my CB550 ran so badly when I bought it.

What probably made mine worse still was that the resistance of the plug caps when checked on a multimeter (if you have access to one) was very high, they should be 5k ohms; two of mine were about 9k ohms and the other was 13.  It's a wonder really that there was any spark at all I guess.

New D7ES plugs and new caps, less than £20 all in, and ignition problems all sorted.

I hope this helps!

Brian.

 worth bearing in mind,as the caps get used,the resister can burn out,and give a much higher reading,
so if you start getting ignition issues,check the caps as well !!!
Title: Re: Spark plugs
Post by: florence on April 19, 2019, 08:30:46 PM
hmm, D7ES out of stock but they do have D7EA.  Does anyone know the difference?
Title: Re: Spark plugs
Post by: Brian. on April 19, 2019, 08:37:32 PM
hmm, D7ES out of stock but they do have D7EA.  Does anyone know the difference?

Well, I don't; but however you look at it they are wrong in some way & you don't want another set of wrong ones so maybe best hang fire until they come in to their stock, or buy from somewhere else?

Brian.
Title: Re: Spark plugs
Post by: Nurse Julie on April 19, 2019, 08:38:38 PM
No idea what the difference is but EA will be fine. We use D7 or D8EA on all our old Hondas.
Edit.....and they all run spot on 😀😀
Title: Re: Spark plugs
Post by: Seamus on April 20, 2019, 12:18:19 PM
Out of curiosity, what is the effect of running non resisted plugs and non resisted caps?
I have dyna ignition and coils, non resisted plugs and caps. Should I be running DR77ES.
Title: Re: Spark plugs
Post by: K2-K6 on April 20, 2019, 01:53:20 PM
I feel these combustion chambers were researched and developed to use resisted ignition system.

It's often just referenced to radio interference,  but it changes the length of spark which is intrinsic to combustion chamber design. I don't think they should be run without resistance.
Title: Re: Spark plugs
Post by: Bryanj on April 20, 2019, 04:41:08 PM
D7EA is the new number for D7ES in the NGK catalogue.
Title: Re: Spark plugs
Post by: deltarider on April 22, 2019, 08:08:44 AM
I feel these combustion chambers were researched and developed to use resisted ignition system.

It's often just referenced to radio interference,  but it changes the length of spark which is intrinsic to combustion chamber design.
Any proof for that? The internet is full of unproven claims.
Title: Re: Spark plugs
Post by: SteveD CB500K0 on April 22, 2019, 09:17:17 AM
Basic electronics Delta.

The spark plug acts like a capacitor. Put a resistor in series and you get a low pass filter (low frequencies get through).

This has the effect of rounding off the sharp “attack” edge of the voltage pulse to the plug, softening and lengthening it.

The high frequency interference is caused by the sharp attack edge of the pulse, so soften it and you get less interference.

The shaping of the spark pulse helps the fuel burn (as long as the combustion chambers are designed to use it).

But I’m an electronics engineer not a mechanical so my knowledge stops there!


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Title: Re: Spark plugs
Post by: K2-K6 on April 22, 2019, 09:18:15 AM
It's a much more intricate area than is readily given importance to I feel, and dominated by the bigger and fatter the spark,  then the better it is stance. That seems more marketing huff and puff than based on factual engineering. 

Do you mean with reference to the R&D specifically related to resisted ignition,  or how resistance affects spark and ignition effects?

It may,  by way of logical explanation be more relevant in the thread I was writing about detonation than isolated as it's really an extension of that field from an informative point of view.
Title: Spark plugs
Post by: SteveD CB500K0 on April 22, 2019, 09:23:38 AM
Love how the “D” in R&D gets turned into a smiley


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Title: Re: Spark plugs
Post by: K2-K6 on April 22, 2019, 09:45:13 AM
I crossed over with you there Steve so may seem slightly out of sync.

My D is not showing smiley on Android tablet  :)

Interesting to get electronic engineer view of it. 

As you say the lengthening of spark assists mechanical layout of combustion chamber.  Combustion is often mistakenly viewed as single time event of explosion by people selling "high power" ignition systems.  Reality is its a controlled burn with progressing stages.  These engines have a fairly conservative design (evidenced by the total ignition advance being around 35 degrees) and rely on the squish area pushing unburnt mixture toward the spark location on approach to peak combustion pressure. Any lengthening of spark duration would be a welcome characteristic to facilitate this design.

It follows that if they required suppression for their developing markets, USA etc,  then the engine design would incorporate that element as a primary lead during development, making it logical that they should always be run with resistance to fit that specification.

If you flip the analysis,  and now remove resistance,  the resulting shortening of spark duration should have a detrimental effect on completion of combustion burn.  It can also lead to detonation.
Title: Re: Spark plugs
Post by: deltarider on April 22, 2019, 11:21:28 AM
In all the automotive literature (at least that I have read) there isn't a single hint to this. But... I am always eager to learn. Tell me where I can find it (internet fora excluded) and I will have a look at it. From what I know a 10kΩ dissipates more energy into heat than for instance a 5kΩ resistor. In spite of having asked around multiple times, nobody so far has delivered any proof for this 'lengthening' of the spark duration.
Title: Re: Spark plugs
Post by: Nurse Julie on April 22, 2019, 12:23:08 PM
Blimey, this is all too tech for me. It's s spark plug and it sparks. D7ES's haven't been around for a long while as far as I can remember so the 'new' or 'alternative' or 'superseded' is the EA type which work perfectly well on all our bikes.
Title: Re: Spark plugs
Post by: K2-K6 on April 22, 2019, 01:37:03 PM
I've linked to this before,  be interesting what you feel about it in this context.

https://www.crypton.co.za/Tto%20know/Ignition/burn%20time.html

The statement directly following the graph references spark duration. 
Title: Re: Spark plugs
Post by: K2-K6 on April 27, 2019, 01:27:14 PM
In all the automotive literature (at least that I have read) there isn't a single hint to this. But... I am always eager to learn. Tell me where I can find it (internet fora excluded) and I will have a look at it. From what I know a 10kΩ dissipates more energy into heat than for instance a 5kΩ resistor. In spite of having asked around multiple times, nobody so far has delivered any proof for this 'lengthening' of the spark duration.

I've been thinking about this statement,  and tentatively agree that the fixed resistance in HT circuits doesn't,  in itself, makes the spark duration change.

Change of spark duration appears as a result of resistance across the spark plug gap seems to be accepted as true.  The variations in pressure, fuel mix, atomisation etc, give a variety of changing conditions which alter the ionisation phase (spark propagates across gap) different start and termination qualities then exist.

How true it is I'm not sure,  but it seems that originally resistance in HT was initiated in aero engines to better control the harmful degradation of plug electrodes and so increase service life along with reliability.  Interference of other systems seems to have been a byproduct.

The fixed resistance appears to give a "collar" to bring a minimum threshold at which the secondary coil is charged before release,  a bit like a wier on a river, making available the quantity of volts to reliably cross the gap consistently.
That's interesting on these systems with two plugs on one coil. Firing the non loaded plug may be easier for the coil to exit through (non power stroke and combustion pressure needs less volts) making it vulnerable to reduced sparking on the power cylinder (the important one).  Making sure the two routes out have the same system resistance looks to be intrinsic to power cylinder performance. 

Checking that the caps are matched pairs would seem to be useful as some measured on her have shown discrepancy in the past.
Title: Re: Spark plugs
Post by: Johnwebley on April 27, 2019, 06:56:54 PM


  interesting discussion ,

 I run Boyer ignition,boyer coils and 5K ohn caps.

 I tend to also have 32thou plug gaps,

I am more than happy with starting and power ,
when fitting new plugs ,if set to 27thou the bike feels a little sluggish,


  any thoughts ? comments ?

 
Title: Re: Spark plugs
Post by: Bryanj on April 27, 2019, 09:43:37 PM
I seen to remember Boyer saying to increase gap John
Title: Re: Spark plugs
Post by: K2-K6 on April 28, 2019, 10:31:31 AM
They've a setup that's not fully disclosed,  Boyer that is, making it difficult to comment on their settings.

We've asked them from the forum before but they wish to keep confidential their methods for commercial reasons,  which you can understand.

They obviously know what they're doing,  make very good systems and it's rare to find criticism of them,  so you have to go with their advice or definite individual experience. 

From a general discussion point of view,  the plug gap offers the ultimate resistance in the circuit. So wider gap (with same coil resource)  would imply shorter duration spark,  but if the gap is wider and causes more volts to build in HT circuit before it jumps, then that may in itself provide more resources to prolong arc time.  It seems a very movable set of parameters as each one influences the other.

If it runs best at 32thou,  then I can't see any problem with that. 

They have previously had info on their site (can't find it now) that indicates multi firing of plugs under certain conditions,  it's not clear if that is driven by circuit load sensitive measurements or just run out of their chip controlling strategy to set parameters programmed in.

They also seem to fire all of the plugs all of the time,  which I don't understand the reason for.
Title: Re: Spark plugs
Post by: florence on May 01, 2019, 12:29:23 PM
Thanks to everyone for the advice.  It has paid off, new coils, new plug caps and correct plugs and all runs very sweetly indeed.

Title: Re: Spark plugs
Post by: mike the bike on May 01, 2019, 07:47:05 PM
Reading this thread had got me wondering if my HT caps are within spec.   I need to have a measuring session.
Title: Re: Spark plugs
Post by: deltarider on May 01, 2019, 08:59:38 PM
Reading this thread had got me wondering if my HT caps are within spec.   I need to have a measuring session.
Caps do detoriate over time. I remember back then there were aftermarket 10.000km (6000 miles) service kits* that did not only include sparkplugs, filters and oil, but also plugcaps. Now in my experience they live longer than 10k but they do detoriate and resistance will increase.
*I believe the brand was Dino.
Title: Re: Spark plugs
Post by: florence on May 02, 2019, 03:25:41 PM
I would second that, the old caps had been on for 24 years and I think the plugs were the same age, so it was about time really.
Title: Re: Spark plugs
Post by: JezzaPeach on May 10, 2019, 12:59:16 PM
If you haven’t already bought I got (standard) 4x DR7ES from salvagehunter15 on eBay for £7.12
Title: Re: Spark plugs
Post by: Nurse Julie on May 10, 2019, 01:12:08 PM
If you haven’t already bought I got (standard) 4x DR7ES from salvagehunter15 on eBay for £7.12
Not sure if you have checked (most probably) but just make sure your plug caps do not have resistors fitted before fitting those plugs, which are also resisted.
Title: Re: Spark plugs
Post by: Johnwebley on May 10, 2019, 05:07:12 PM
If you haven’t already bought I got (standard) 4x DR7ES from salvagehunter15 on eBay for £7.12


  Ideally D7EA  are prefered
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