Topic: Sparkplug wires: iron or copper core?

[Deltarider]

Sparkplug wires come with iron or copper core. What's the difference?
BTW, carbon core and our bikes is not a good match.

[Bodi]

I believe it doesn't matter. I would get copper just because it is easily available. If you can only get iron or some other alloy no problem.
Some resistance wires are just fine, but hard to find: 100 Ohm/foot ok, 1000+ Ohm/foot not great, 12K Ohm/foot avoid. But typical resistance wire sold by the foot at your local auto parts store is likely 12K. Stock ignition likes around 10K total, 5K per plug either 5K caps or R plugs. No resistance gives a very short spark - the resistance extends spark duration. Also reduces EMF if that is a concern.

[Deltarider]

[...]
Some resistance wires are just fine,[...]

The resistance is not the problem, it is the carbon that will become brittle.

Stock ignition likes around 10K total, 5K per plug either 5K caps or R plugs. No resistance gives a very short spark - the resistance extends spark duration.No resistance gives a very short spark - the resistance extends spark duration. [...]

I wonder how you know this.

[seanbarney41]

At least around my neck of the woods, it has gotten very hard to get non-resistor plugs...ever since NGK discontinued all of them.

[Bodi]

"I wonder how you know this."
...
Ohm's Law.

[kyle750]

I recently bought 4m of vintage 7mm Packard 440 ignition wire to replace my old, cracked, and in overall poor condition spark plug wires.  The Packard 440 inner wire is silver but my understanding is that it is not steel but stranded copper wire that has been tinned silver to prevent corrosion. I could be wrong.   

[HondaMan]

[...]
Some resistance wires are just fine,[...]

The resistance is not the problem, it is the carbon that will become brittle.

Stock ignition likes around 10K total, 5K per plug either 5K caps or R plugs. No resistance gives a very short spark - the resistance extends spark duration.No resistance gives a very short spark - the resistance extends spark duration. [...]

I wonder how you know this.

One way: a very long time ago (around 2006?) I posted oscilloscope traces of resistor vs. non-resistor plug firings in a rather long post about the differences between the Dyna 3-ohm, TEC 4.6 ohm coils (i.e. early CB750, prior to 1973) and Dyna 5-ohm coils. With the 3-ohm coils I also included traces of the firing with the 2.0 ohm Resistor Pack I had just developed for the bikes that were struggling with low battery problems due to too high currents with the 3-ohm coils. I also used the OEM 5k plug caps and the 10k plug caps (I didn't have any 0 ohm plug caps then) and one trace with an old 7.5k ohm cap pair (which had aged to about 8.1k ohms by the test time) from my own 750's leftovers.

Among the [many] observations I (and others) made from the traces, the spark DURATION was noticeably longer as shown by the oscillations that comprise the discharge back-and-forth across the electrodes: the 3-ohm coils were about 5 back-and-forth excursions between the electrodes with 5k plug caps and sometimes (not consistently) 6 oscillation with the 10k plug caps. With the 4.6 ohm coil the discharge oscillations were 7 times before they couldn't jump the plug gap anymore with 5k plug caps and 8 or 9 (back-and-forth) with the 10k caps. With the 5-ohm coil it ran about 1 more oscillation (10 most of the time) for both the 5k and 10k plug caps. Using the 7.5k-ish plug caps it predictably fell off about 1 plug gap jump compared to 10k caps, but I only ran that test with the 4.6 ohm coils.

At one time that post was in the Thoughts of Hondaman collection that someone made, but I don't think it's there anymore?

[scottly]

No resistance gives a very short spark - the resistance extends spark duration. Also reduces EMF if that is a concern.

This is incorrect. The secondary resistance has nothing to do with the duration of the spark. I don't know where this myth got started?? Think about it, if the resistance of the wires was that critical, what about cars with resistance wires that varied in length by 2 feet or more, or that Hondas worked with 5K or 10K plug caps? The peak secondary voltage as displayed on a scope will be higher with more resistance, but the duration is unchanged. The duration is determined by the L-C time constant of the coil inductance and the condenser.

The sole purpose of resistance in the secondary is for RFI suppression, especially in the AM radio band. Please don't make me drag out my college textbooks again.

[Deltarider]

Scottly, I thank you from the bottom of my heart. Where I have not succeeded in many, many years, hopefully you will.
Here's a question for those who still doubt. There are quite a few owners that run a CDI ignition on our bikes. Although I opted for a transistor ignition myself, they seem to be happy with them. Realise that CDI ignites with a very short peak voltage and there's no spark duration to speak of.
Ask anyone if they have noticed any improvement after adding resistance in the secundary circuit. I have not seen or heard of any. I myself have had zero resistance, 5kOhm and 10kOhm in my wires and never noticed any difference.
If added resistance was sooo important, you would expect Honda to have a few lines on this subject in their elaborate manuals. There are none.
The advice Honda The Netherlands once advised me: have 5kOhm.
Honda France even advised to bin sparkplug caps when over 8kOhm.
Finally, if there's anything I wish to see in this forum, it would be that members stop parroting nonsense.

[Don R]

 I'm running the Gerex CD version of their ignition box. It doesn't fail to fire the plugs. I have 5K caps and solid tractor wires from a farm store kit.