Spark plugs

Holister · 1 Spark plugs on Sat Mar 19, 2016 12:27 am

Holister

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My sparkplugs (D7EA) get replaced every 10K km. That's not a routine I have, its when the SPs fail and it's always around that mark give or take a few hundred km. I first notice a slight roughness at startup and after a few days I can feel slightly more vibration thru the bars. I pull the plugs and they look fine... a nice colour, but when I put the meter on them it tells a different story. At least one will read over 100 ohm. Last time I had 3 dud SPs. I chuck the duds and throw 1 or 2 in the tail for emergencies. Never had to use them tho.

I'm now 8K klm into my present set of SPs and this week I get that roughness on startup. I pull the plugs to find 2 are dud. Bugger. I should have another 2K to go. Lucky I have a set I ordered online (half price) coming next week.

This just got me wondering....
What SPs do other members use? There are a few specialty type plugs available.
How often do you replace them?
Does any one else test their plugs with a DMM?

Cheers

duck · 2 Re: Spark plugs on Sat Mar 19, 2016 12:55 am

duck

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NGK DR7EIX. They only last about 40 or 50 thousand miles though.

rawdonball · 3 Re: Spark plugs on Sun Mar 20, 2016 10:55 am

rawdonball

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Hey Kaptain - that's quite an eye opener given that I have same plugs as you run, on all my K bikes and I've only change one set of four plugs (yesterday)! I guess they all run so rough compared to yours that a little rougher goes un-noticed...

Tell me again about the theory? What should new plugs read? Do you start to pick up a drop in insulation resistance as the plug ages and is this associated with weaker spark due to leakage current instead of everything jumping the gap?

Two Wheels Better · 4 Re: Spark plugs on Sun Mar 20, 2016 7:21 pm

― George Orwell, 1984

RicK G · 5 Re: Spark plugs on Mon Mar 21, 2016 12:19 am

RicK G

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Check to see if you have been buying fakes

WoodyAUK75 · 6 Re: Spark plugs on Mon Mar 21, 2016 9:01 am

WoodyAUK75

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Wow, that's unreal Rick! I wonder if the local distributor got a shipment of fakes. I stopped using NGK about 10yrs ago after a couple of bad runs. The local servo gets me X5DCs and I change them when ever I can't remember how long ago I put them in. Then I keep the old ones under the seat because there's nothing wrong with them anyway.

Holister · 7 Re: Spark plugs on Tue Mar 22, 2016 6:04 am

Holister

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@rawdonball wrote:Hey Kaptain - that's quite an eye opener given that I have same plugs as you run, on all my K bikes and I've only change one set of four plugs (yesterday)! I guess they all run so rough compared to yours that a little rougher goes un-noticed...

Tell me again about the theory? What should new plugs read? Do you start to pick up a drop in insulation resistance as the plug ages and is this associated with weaker spark due to leakage current instead of everything jumping the gap?

Rawdon.... No theory. What I'm measuring is the continuity of the electrode in ohms. What happens is the electrode, somewhere along its length from the terminal nut at the top to the insulated tip at the bottom, breaks down and becomes resistive. I'll take an educated guess and say that is because of some minute fracture due to heat and vibration. The wider the fracture the higher the resistance. When the plug is cold its worse. As the plug heats up it seems to conduct better.
What I experience is a slightly harder start and rough idle which disappears when the engine is up to running temp although at higer rpm I feel a very slight increase in vibration. I can usually get about for another week or two but eventually one or more of the plugs will fail completely.
The point of my original post is that I think I should be getting better milage out of a set of plugs.

I've taken some pics of my latest test to show what I'm talking about. These plugs have done 8K km. They're clean and showing no sign of electrode wear. You wouldn't expect any at 8K. If anything I think they look like she's running a little lean. I think my TB rubbers are leaking. #3 looks slightly dirty but that's another issue.

With The DMM set to 200 ohms scale, attach one probe to the terminal nut and probe the insulated electrode with the other. You might need to clean it off or scratch the surface with the probe. As a reference, when you touch the probes together you'll get around 0.3 ohms ie; no resistance apart from a very small amount in the probe wires.

Testing for earth leakage using a DMM is not a viable test because HT votages will easily overcome high resitance. A DMM is operating at less than 9V.

rawdonball · 8 Re: Spark plugs on Tue Mar 22, 2016 6:42 am

rawdonball

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Great post thanks 'My Kaptain"

My K100RS '85 with its brand new set of NGK D7EA plugs from motobins (have I got that right?) is taking multiple goes to get it to idle. It fires early but dies as soon as I touch the throttle - seems like I have the cold is bad / warmer improves, syndrome you were describing..

Now to find my DMM!!!!

charlie99 · 9 Re: Spark plugs on Tue Mar 22, 2016 7:39 am

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you may have one or several issues ...looking at plug 3 to start with it looks about right ...perhaps a just a tad rich ... but considering the rest there is something wrong

the rest look to be running lean to blazes ...that in itself will cook a plug very quickly ...perhaps a cooler heat range might be in order till you find the core issue ...for the mix you are presenting to the cylinders and the plug cables - coils are sorted .

meanwhile sorry to say But your testing method is completely flawed .

if a parallel resistance is to earth it could read anything , and it looks that way to me that you've shown in the pics . please tell me that you weren't touching the earthy side as well as the central electrode ??!!

1> you should test the thimble to central electrode WITHOUT TOUCHING THE GROUND ELECTRODE AT ALL . else parallel resistances can confuse the issue . I would expect the resistances to be in the lowish hundreds of ohms if faulty and nearly zero if ok 1.1 ohms sounds about right on a non resistive type plug .

2> you should be testing the central electrode to the earthy side ...I would be expecting meg ohms to hundreds of thousands of ohms resistance but obviously it has baked carbon deep down in there ..away from the tip who knows what it is really.

plugs will suffer from overheating and go partially open circuit as the copper electrode melts inside the ceramic from the extreme temps of a lean plug .

yes your right you cannot expect to see the real resistances under compression load ...without a high voltage source

a multi meter is not the right way to go in this case ...it can prove there is a short or open circuit at low voltage ....but that's it ...at 30,000 volts it means bugger all

point in hand, remember the rd 250 and 350 yamahas ...to flood them is quite easy ....to measure that flood across the plugs was impossible with a multi meter ....

put in fresh plugs and away you go, till the old ones died out or were cleaned

this is aimed at d7ea plugs ...not dr7ea which have about 5000 ohms built in with carbon before the electrode in the combustion chamber

Holister · 10 Re: Spark plugs on Tue Mar 22, 2016 9:50 am

Holister

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@charlie99 wrote:you may have one or several issues ...looking at plug 3 to start with it looks about right ...perhaps a just a tad rich ... but considering the rest there is something wrong

the rest look to be running lean to blazes ...that in itself will cook a plug very quickly ...perhaps a cooler heat range might be in order till you find the core issue ...for the mix you are presenting to the cylinders and the plug cables - coils are sorted .
Yep. I did say they were lean. I've been thinking about trying a D8EA. I tested my leads and coils early last year with a good result. Might look at that again, but leads will be replaced shortly.

meanwhile sorry to say But your testing method is completely flawed . With great respect charlie, I don't think so

if a parallel resistance is to earth it could read anything , and it looks that way to me that you've shown in the pics . please tell me that you weren't touching the earthy side as well as the central electrode ??!!
Nothing was earthed. In those photos I was not touching the SPs. Probe was clipped to the threaded top. I tested them several times and got the same result even after running the bike for a few days in between. I can assure you I am very familiar with using a DMM and testing procedures.

1> you should test the thimble to central electrode WITHOUT TOUCHING THE GROUND ELECTRODE AT ALL . else parallel resistances can confuse the issue . I would expect the resistances to be in the lowish hundreds of ohms if faulty and nearly zero if ok 1.1 ohms sounds about right on a non resistive type plug.
NO WHERE IN THOSE PHOTOS DO YOU SEE ME TOUCHING THE ELECTRODE OR GROUND.
The faulty ones ARE in the "lowish hundreds of ohms".... That's where I'd expect the resistance values to be also.
As far as I can remember, all the new SPs I've measured were < 0.5 ohms

2> you should be testing the central electrode to the earthy side ...I would be expecting meg ohms to hundreds of thousands of ohms resistance but obviously it has baked carbon deep down in there ..away from the tip who knows what it is really.
Correct. But any breakdown of the ceramic insulation would be difficult to detect/measure with a DMM. You'd need a mega to do that. Any resistance you could measure with a DMM would be in the megohm range, as you say, but would mean the plug had already stopped working by that stage.
plugs will suffer from overheating and go partially open circuit as the copper electrode melts inside the ceramic from the extreme temps of a lean plug .

yes your right you cannot expect to see the real resistances under compression load ...without a high voltage source

a multi meter is not the right way to go in this case ...it can prove there is a short or open circuit at low voltage ....but that's it ...at 30,000 volts it means bugger all
Its simply a test to determine the integrity of the SP electrode which I think is quite valid, in the same way you measure the resistance in a lead or coil using a DMM

point in hand, remember the rd 250 and 350 yamahas ...to flood them is quite easy ....to measure that flood across the plugs was impossible with a multi meter ....

put in fresh plugs and away you go, till the old ones died out or were cleaned Yes. I remember the old RD very well but I haven't a clue about measuring the "flood accross the plugs"

this is aimed at d7ea plugs ...not dr7ea which have about 5000 ohms built in with carbon before the electrode in the combustion chamber I mentioned I was using D7EA in my OP

Thanks for your input charlie. I think you're right. She's running a bit lean. probably more than I thought. The old girl is coming up for a make-over very shortly. Will be stripping her down to tidy up a few odds and ends such as replace the TB rubbers, new HT leads and a few other jobs.
I've always thought she ran a little hot so this, as you say, is probably why the plugs are not lasting. I might try a set of cooler plugs in the meantime.
Cheers mate Very Happy

92KK 84WW Olaf · 11 Re: Spark plugs on Tue Mar 22, 2016 11:02 am

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I have been using NGK D8EA on the advice of a well known local guy and never had an issue with these. Using them 6 years so go right ahead,

charlie99 · 12 Re: Spark plugs on Tue Mar 22, 2016 3:22 pm

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1> you should test the thimble to central electrode WITHOUT TOUCHING THE GROUND ELECTRODE AT ALL . else parallel resistances can confuse the issue . I would expect the resistances to be in the lowish hundreds of ohms if faulty and nearly zero if ok 1.1 ohms sounds about right on a non resistive type plug.
NO WHERE IN THOSE PHOTOS DO YOU SEE ME TOUCHING THE ELECTRODE OR GROUND.
The faulty ones ARE in the "lowish hundreds of ohms".... That's where I'd expect the resistance values to be also.
As far as I can remember, all the new SPs I've measured were < 0.5 ohms

sorry nigel it looked to me as if you were touching the side electrode and the central electrode at the same time ....the side electrode is the earthy side or ground electrode which I why I posted in the first place

sorry for the rant everybody

I appreciate manipulating the spark plug is rather difficult and getting the multimeter and probe in frame as well
perhaps a better picture like this could have helped delineate the central to the side electrode measurement ?

I get what you trying to do but could be confusing to newbies without prior experience ?

this plug by the way ...with 20,000 ks on it measured about 1.9 meg ohms but still works ...sorta kinda

rawdonball · 13 Re: Spark plugs on Tue Mar 22, 2016 10:27 pm

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"What happens is the electrode, somewhere along its length from the terminal nut at the top to the insulated tip at the bottom, breaks down and becomes resistive"

Good sentence this Kaptain - goes well with Charles99's clarification.

Should get my DMM back today - left it in a car which I then lent to a mate! What hope is there for some of us 'youngsters'...

Holister · 14 Re: Spark plugs on Tue Mar 22, 2016 11:55 pm

Holister

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Charlie. I realise now the point you were trying to make. My probe was in contact with the outer earth electrode. I thought you were refering to me 'touching' parts of the SP (fingers) but I can assure you that nothing was in contact with the ground/shell of the SP. The SP earth was totaly isolated so it did not affect the reading from the centre electrode. Also I had earlier done the measurement ensuring the earth electrode was not in contact... same result. The photos may have been a little misleading (I normally pay attention to those sorts of detail) but I stand by the readings as shown in each. I repeated them several times and they are the same.

I started my bike this morning and the #2 Sp is now totaly open circuit. Fortunately, about an hour later my mail order SPs arrived. How's that for timing.

but unfortunately they are D7EAs. I'll see what I can find locally. I think SuperCheap Auto have the 8s.

Cheers

charlie99 · 15 Re: Spark plugs on Wed Mar 23, 2016 6:29 am

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yes seen them there

it might be time to check the fpr captain

and possibly a leaky injector ? or a good clean up of all the injectors as a first point service ?

klompy the grey brick · 16 Re: Spark plugs on Sun Jul 10, 2016 5:19 am

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Hi guys I believe I know the difference between DR8EA and D8EA the inbuilt resistance suited to the coil that is either 12 or 9 volt....ok I know a bit about it.....so why does NGK tell me to install DR7EA or DR8EA for my K1100 and some of you folk run the no resisted versions.

As pauline would say "Please explain"

Cheers Klompy

92KK 84WW Olaf · 17 Re: Spark plugs on Sun Jul 10, 2016 5:48 am

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As far as I remember, after being corrected on the forum is that the 16 valve engines use the resistor plugs, denoted by the R in the code. 8 valve engines do not, the plug leads differ and incorporate the resistors.

I have D8EA in my K100 [8 valve] and can't seem to find D7EA here. They are cheap and cheerful but do not seem to have a very long life.

charlie99 · 18 Re: Spark plugs on Sun Jul 10, 2016 6:53 am

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klompy

the k1100 and 16 valve units have a very different coil impedance on the primary ...thus making the secondary a higher voltage to the plugs
yes the k1100s do have the same resistive type leads, but the ignition durations and current available is a little different because of the step up ratio

so lets predict that the wattage available from the lower primaries is higher ...ie 12 divided by 1.5 ohms (or something ) gives a current of about 6 amps x 12 volts = 72 watts pulsing ...where as the k100 is somewhere less ... the amount of spark energy available can be further current limited by the r series plugs so that a higher spark voltage is achieved ..( but a little less current involved ) which could make the electrodes last longer as the pitting phenomenon is less pronounced ...and the mixture is differently mapped once you go to the motronic rather than the le jetronic computers and the extra induction available on the 4 valve / per cylinder valve units

does that help ?

RicK G · 19 Re: Spark plugs on Sun Jul 10, 2016 6:55 am

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The ignition systems are very different and using DR7EA will keep the coils very happy.

92KK 84WW Olaf · 20 Re: Spark plugs on Sun Jul 10, 2016 7:01 am

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@RicK G wrote:The ignition systems are very different and using DR7EA will keep the coils very happy.

For the K1100RS....

klompy the grey brick · 21 Re: Spark plugs on Sun Jul 10, 2016 7:21 am

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and K1100LT :O)

RicK G · 22 Re: Spark plugs on Sun Jul 10, 2016 9:28 am

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Yeah both

Gaz · 23 Re: Spark plugs on Sun Jul 10, 2016 7:41 pm

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As a useful reference for this discussion, here is page 74 of the BMW Riders Manual for the K1100 RS/LT regarding spark plugs.

The cross reference to NGK is DR7EA and like Rick G my bike has been happy having used these for 100,000km on my K1100LT changed at intervals such as "gee it's a fair while since I've changed the plugs" and have had no trouble.

Cheers

Dai · 24 Re: Spark plugs on Sun Jul 10, 2016 8:58 pm

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Gaz80 wrote:changed at intervals such as "gee it's a fair while since I've changed the plugs" and have had no trouble.

You too eh? Very Happy

Chassis number	0019026
Vehicle code	0503
Series	K589
Model	K 100 RS 83 (0502 ( 0503 )
Body type	K 100 RS 83 (0502
Catalog model	ECE
Production date	1984 / 07
Engine	0513)

Chassis number	0019026
Vehicle code	0503
Series	K589
Model	K 100 RS 83 (0502 ( 0503 )
Body type	K 100 RS 83 (0502
Catalog model	ECE
Production date	1984 / 07
Engine	0513)

1 Spark plugs on Sat Mar 19, 2016 12:27 am

Holister

2 Re: Spark plugs on Sat Mar 19, 2016 12:55 am

duck

3 Re: Spark plugs on Sun Mar 20, 2016 10:55 am

rawdonball

4 Re: Spark plugs on Sun Mar 20, 2016 7:21 pm

Two Wheels Better

― George Orwell, 1984

5 Re: Spark plugs on Mon Mar 21, 2016 12:19 am

RicK G

6 Re: Spark plugs on Mon Mar 21, 2016 9:01 am

WoodyAUK75

7 Re: Spark plugs on Tue Mar 22, 2016 6:04 am

Holister

8 Re: Spark plugs on Tue Mar 22, 2016 6:42 am

rawdonball

9 Re: Spark plugs on Tue Mar 22, 2016 7:39 am

charlie99

10 Re: Spark plugs on Tue Mar 22, 2016 9:50 am

Holister

11 Re: Spark plugs on Tue Mar 22, 2016 11:02 am

92KK 84WW Olaf

12 Re: Spark plugs on Tue Mar 22, 2016 3:22 pm

charlie99

13 Re: Spark plugs on Tue Mar 22, 2016 10:27 pm

rawdonball

14 Re: Spark plugs on Tue Mar 22, 2016 11:55 pm

Holister

15 Re: Spark plugs on Wed Mar 23, 2016 6:29 am

charlie99

16 Re: Spark plugs on Sun Jul 10, 2016 5:19 am

klompy the grey brick

17 Re: Spark plugs on Sun Jul 10, 2016 5:48 am

92KK 84WW Olaf

18 Re: Spark plugs on Sun Jul 10, 2016 6:53 am

charlie99

19 Re: Spark plugs on Sun Jul 10, 2016 6:55 am

RicK G

20 Re: Spark plugs on Sun Jul 10, 2016 7:01 am

92KK 84WW Olaf

21 Re: Spark plugs on Sun Jul 10, 2016 7:21 am

klompy the grey brick

22 Re: Spark plugs on Sun Jul 10, 2016 9:28 am

RicK G

23 Re: Spark plugs on Sun Jul 10, 2016 7:41 pm

Gaz

24 Re: Spark plugs on Sun Jul 10, 2016 8:58 pm

Dai