Topic: Graphite Core or Copper Core spark plug wires

[brandEn]

So today I went to get some 7mm spark plug wire so I could make new plugs. I figured no prob, I will just hit the parts store and knock it out. Yea right. Nobody carries copper core plug wires, even a performance hot rod shop and custom Harley shop I went to. In fact the only place I could find that sold bulk wire was Napa and its graphite core.


I got some since it was only like $6 for 8 feet and then came home and ordered copper core. I made the new plugs with the graphite core, NGK 5 ohm resistor caps, and new NGK resistor plugs. The bike seems to run just fine but it got me wondering. What's the difference between the two types of wire and why is copper core preferred on these old bikes?   

[millerza]

I put unshielded wires, dont know if they are copper, on mine but they really screw with my LED taillight.

[bjbuchanan]

go to autozone and look at like the bottom right of the plug wire display. always in the same place

accel super stock wires. copper core, no suppression, nice silicone jacket. I just did this to my coils like 2 months ago. its 20$ or so and you get enough wire to do like 4 bikes no joke

You can use resistor plug caps or use the ones on the wires already and run a resistor plug. I did the latter

oh nevermind

graphite core has some suppression abilities i believe. its not as good as dedicated suppression wires but better. copper core is preferred because it has the least resistance and the system works with it, its the original design

[brandEn]

Wish I would have known that BEFORE I ordered some wire a few hours ago. Oh well. Is that Accel wire available in black or is all yellow?

[bjbuchanan]

all yellow unfortunately but what i did was just put shrink tubing on the wires before i connected them. 1/4 inch i think then some heat and it looks real good. if you want pretty colors you could just get it from autozone as well while you are there, its near the crappy crimp terminals

[Don R]

tractor supply, get a 4 cyl tractor set, it's enough for 2 sets and cheap.

[Irukandji]

AT NAPA

Belden Max ....#700172

[brandEn]

AT NAPA

Belden Max ....#700172

http://www.napaonline.com/Catalog/CatalogItemDetail.aspx?R=BEL700172_0165431295


Nice, Thanks.

[TwoTired]

The original ignition wires were stranded steel core.
I reason this was chosen because the plug caps screw into the end of the wire and copper is really too soft for screw thread abrasion and a reliable long term connection/contact.

Graphite core wire has a resistance rating per foot and is often called suppression wire.
It's not a particularly good idea to have resistance in the plug caps, the spark plugs, AND the interconnect wire, unless there is some really high voltage charging into the spark gap.  The kind of voltage you just don't get with the stock coils and points.

As usual, the ignition circuit should be considered as a subsystem made of individual components.  Changing a part or component of the system generally has an impact on how the entire system functions.  If not under ideal or normal conditions, then perhaps in some extreme condition like age, temperature, system voltage weakness, or points/condenser capability, etc.

Cheers,

[brandEn]

Thanks TT. Great post!

[andrewk]

FWIW, Accel makes wires in a few different colors, and black is one of them.  You may have to special order it from a parts store, though.

Not sure where you'd find stranded steel ignition wire these days, but the copper holds up pretty well in my experience. 

[70CB750]

Could somebody tell me why not use just car cables - boots and everything? No more caps screwing on, available ewerywhere and just use resistor plugs?

I am never afraid to ask dumb question

[bjbuchanan]

Thats what i did, just plain straight boots. You just wanna try to get the stock resistance in the circuit or you burn up the points much faster. I used no resistance boots and a 5k ohm plug to get back to stock for a 750

[Bodi]

Secondary (the spark plug part) resistance shouldn't affect the points. The secondary resistance reduces the peak spark current and extends the spark duration but has little effect on the primary circuit. Reduced spark amperage reduces the electromagnetic energy pulse produced, this reduces interference in nearby AM radios. Having no resistance in the plug circuit can produce enough interference to cause problems with bike electronics as well, electronic ignitions in particular.
The extended spark duration should make for better mixture ignition as well. You shouldn't run all copper wire without resistor plugs or caps. Using resistor caps, resistor plugs, and graphite core resistor wire is not a good plan either. I suggest either resistor plugs OR resistor caps and copper plug wires. Non-resistor plugs can be hard to find, so the idea of using the molded cap wires from a tractor or other vehicle 4-cyl metal core plug wire set and resistor plugs has some merit. Attaching the coils is difficult with the hardwired stock coils, but other compatible Honda bike coils have re-usable coil connectors and Dyna coils use standard automotive coil connectors.

[brandEn]

Bodi thats a great post as well. Thanks. I am learning something. I actually ordered Dyna copper core wires and was going to cut the plug side off so I could use the NGK resistor caps AND resistor plugs. Your post has me thinking maybe I will just keep the Dyna non resisted caps and use only the resistor plugs with my Dyna 3 ohm coils. Pamco ignition so no points.

[754]

 I want to run RED THUNDERBOLT wires on my magneto..might have 3 from way back but they may be too short. If you run skinny wires, and mount coils under carbs, you can run your wires thru the cylinder block, then arc them up to the plugs with straight boots...looks Killer..imo