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The instructions for my TriSpark specify resistor plugs or caps.
The Surefire recommends them.
As I remember, when I bought a Rita in '82 Mistral said not to use them.
Oddly enough, BMW uses both resistor plugs and caps for the K100. But that ignition box also controls the fuel injection, totally digital.


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From the instructions that came with my Pazon Sure-Fire;

"We recommend fitting NGK 5K resistor (suppressor) type plug caps (or similar good quality make),
but you can also fit non-resistor caps."

Not real clear direction from the manufacturer.


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Originally Posted by Bob B
From the instructions that came with my Pazon Sure-Fire;

"We recommend fitting NGK 5K resistor (suppressor) type plug caps (or similar good quality make),
but you can also fit non-resistor caps."

Not real clear direction from the manufacturer.

What is not clear? They recommend them... but they dont require them so it wont effect the performance of EI being used.

The reason they recommend them is because they don't know what else you have fitted to the bike which may or maynot be affected by interference, if they didn't recommend it and you had another component which was affected then they would be open to all kinds of abuse... This way they cover their arse.


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Kommando--thanks for that video clip.
I had always wondered how they made a resistor plug as compared with a non resistor plug-- but I guess I was always too lazy to find out.
That clip answers my wondering.
Thanks again!

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why does taking a spark plug apart make him breathe so heavily?

this may solve my magneto problem if they're all this simple.


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Just use B7EV or B8EV plugs instead of ES type.

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...may be is better to switch again to Champion but with my dual plug head I did not found yet a 12mm Champion that worked with the N5 or N3.

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Guy in the video did not clean surfaces and reapply loctite. I believe I would...


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What is the "resistor" part he removed actually made of?
How does it work?

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Resistors are (or certainly were) usually a ceramic cylindrical substrate which is then etched or the like to give a long spiral, the "resistor" bit. There are end caps pressed on as connectors. There are high power resistors which are wire wound. Either way, the resistive part is encapsulated. Why on earth you would want to know how a resistor works, I'm not so sure, I worked in a resistor factory some 50-odd years ago, and I'd be fine never seeing another one, though they end up in some shape or form on every pc board you're likely to find

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I used NGK's for years in my vintage Brits till they got hard to find. I switched to Denso W24ES-U with good results. Copper core wires and NGK 5 ohm caps with the Boyer EI's. Recently solved the old jalopy sparkler issue by selling all the vintage bikes (5) kept my 03 Bonny. I use NGK i-ride-um sparklers that have almost 16k miles on them!!!

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The analog EI systems such as Boyer Mk 3 & 4 don't specifically need resistor plugs or caps, but they ARE often needed if you have an electronic rectifier/voltage regulator. I have a Boyer Mk 4 and a Sparx rectifier/regulator, the one that looks the older zener starburst heat sink, under the headlamp.
The fitting instructions for that one specifically said that resistor plugs or caps should be fitted to avoid disturbance to the regulator from the ignition system..


Bike History: Jawa 50 1956, Bridgestone 50/90 Sport 1967, Triumph T120 Bonneville 1970, Yamaha 125 DT125 Scrambler 1974, Kawasaki 125 KE125 Scrambler 1978, AJS model 18 500 Single 1964. Current bike Triumph T100R Daytona 1972.
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Apparently resisters CAN work with magnetos, because the 1960 650cc Triumph parts book shows one, and it is a separate part inserted in the spark plug's cap, between the cap and the ignition wire.

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Resistor plugs will work with a good mag. If you actually consider what they are doing
the resistor in effect, is giving the mag more work to do, it needs to generate a higher
voltage to overcome the combination of the air gap plus the resistance in order to form
an arc or spark. An ancient or mag in poor condition may not be able to do that and may
arc internally etc.

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the system i use requires the magneto coil to fire four plugs at once. not the best choice for plugs that measure at a higher resistance.

nick, i'll look into the EV plugs. i've used ES for decades, but if they work, they work.


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-with a magneto possible the problem will be trying to start the engine and the at idle; I guess.
I do not want to damage the Motogadget speedometer though I want the magneto to performs right, obviously.

I will try to look for information on that EV series but may be they do not sell its here

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Originally Posted by NickL
Resistor plugs will work with a good mag. If you actually consider what they are doing
the resistor in effect, is giving the mag more work to do, it needs to generate a higher
voltage to overcome the combination of the air gap plus the resistance in order to form
an arc or spark. An ancient or mag in poor condition may not be able to do that and may
arc internally etc.

To keep things in perspective, compare the 5,000 ohm suppressor resistance with the resistance of a spark plug gap under compression.

Also consider that even a poor magneto must put 5,000 volts across the plug gap. 5,000 ohm is not a big resistance to 5,000 volts.

I’ll believe that a suppressor plug cap stops a magneto working when I see it happen.

I’ll probably never believe the theory that the suppressor cap puts some sort of damaging strain on the magneto.


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This aeroplane guy did some rudimentary tests, which don’t really answer the question about any palpable effect of low value resistor (5,000 kohm) in an old bike, but still quite interesting.

http://www.viragotech.com/fixit/Resistor%20spark%20plugs%20and%20resistor%20spark%20plugs%20caps.htm


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Originally Posted by kevin
the system i use requires the magneto coil to fire four plugs at once. not the best choice for plugs that measure at a higher resistance.

nick, i'll look into the EV plugs. i've used ES for decades, but if they work, they work.
EV plugs are no longer made,been replaced by the resistor version ...You can find NOS EV's on Ebay for reasonable money..Or just use NGK Competition plugs like I use...But my race bikes do have 5k ohm plug caps for use with the digital ignition..


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Hi,
Originally Posted by Hillbilly bike
EV plugs are no longer made,
Can you still get EG's (nickel centre electrode) or EVX's (platinum centre electrode) without resistors?

Regards,

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Hi NickL,
I’d invite your comment on these thoughts of mine if you would. It would help my understanding. Thanks.

Until the spark strikes, the plug has effectively infinite resistance.

So the only current flowing through a resistor in either a plug cap or plug while the voltage is rising (either from magneto or coil) is a relatively small quantity of electrons from the secondary coil, driven by the enormous voltage spike into the centre plug electrode.
That electrode and the ground are like a capacitor with the poor dielectric of compressed mixture instead of mica, so a spark occurs only when the charge on the plug tip is sufficient.
Only then, and only very briefly, does a current flow. Once the arc has been created, the ionisation means that the gap resistance has dropped to virtually zero. At this time I could imagine the resistor having an influence on the resulting spark strength and duration, not so much on the spark actually happening in the first place.

Admittedly, if coils or a magneto aren’t able to discharge their sparks, they can be damaged. Most mags have a provision for this, coils don’t as far as I know.

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Ask triton thrasher, he seems to know.
99% of the time a plug is not trying to ionise dry air, it is a fuel mixture.
Spark energy is not just volts.

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Originally Posted by Stuart
Hi,
Originally Posted by Hillbilly bike
EV plugs are no longer made,
Can you still get EG's (nickel centre electrode) or EVX's (platinum centre electrode) without resistors?

Regards,
In the US ,BEG plugs are available in #8 and colder...EVX is discontinued. I used EG plugs in my race bike, then used the NGK competion series that a copper core I believe. No difference in performance....I tried EVX in my street 750, no difference in performance.I never had fouling issues in any bike so any plug does the job.
Again, the discontinued plugs are readily available on Ebay, in mass quanties for regular prices...


79 T140D, 89 Honda 650NT ,61 A10 .On a bike you can out run the demons
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In light of the discontinuance of some of our favorite NGK spark plugs, eg. B6ES,B7ES, B8ES, what does the vintage British motorcycle community think about alternate brands that claim to be a suitable alternative to NGK and Champion? There are other brands out there we are looking at, such as Denso and Autolite. Any interest out there?

- Dave


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I'm sold on Denso. I had a problem on the 68 that only happend upon leaving a certain stop sign after a hard uphill canyon run and needing to to cross four lanes of speeding truck traffic. The bike would stutter a bit. Not much but at certain times it could be heart stopping. I chased that stutter for years. Denso cured it.


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