correct spark resistance

[crassius]

yes, I posted that because it was so rare - that one finally died completely after running some more - after hundreds of CDI tests over the years, that was first one to fail, then recover a few times with each recovery lasting a shorter amount of time

for one person to find 5 in a row makes me wonder

 

[gary55]

yes, I posted that because it was so rare - that one finally died completely after running some more - after hundreds of CDI tests over the years, that was first one to fail, then recover a few times with each recovery lasting a shorter amount of time

for one person to find 5 in a row makes me wonder

I know it made me wonder too. I started carefully checking my steps because as a rule the cdi's are pretty sound, the mag's are usually the s**t heads. You know how you do it, you leave a working one in line then switch in and out with those in question. If the one in line works every time, and the ones in question fail then the conclusion is that the ones that are failing are failing. It's hard for me to expound on this.

 

[crassius]

yeah, that's why I built the testing machine that allows me to see spark strength and timing

 

[zippinaround]

hmmm I had fitted a rev counter and a Speedo both wired and were getting interference from the plug so I fitted a ngkr plug it did fix the interference but about a week later my cdi went! this thread woulda saved me a cdi had it been started earlier , i dont even have a multimeter so never test anything. oh well at least now i know.

 

[Frankenstein]

hmmm I had fitted a rev counter and a Speedo both wired and were getting interference from the plug so I fitted a ngkr plug it did fix the interference but about a week later my cdi went! this thread woulda saved me a cdi had it been started earlier , i dont even have a multimeter so never test anything. oh well at least now i know.

So greater resistance generates bigger em currents? I mean I guess that could make sense, but if the CDI just isn't pumping more juice to the wire and plug then shouldn't that field be smaller?

Or is this interference comming from the coil and mag from having excess wattage floating around? Anyone think that looping the mag wires around an iron core like they do for other electronics would reduce interference?

I've even seen those iron loops in the cables of controllers for games and in some USB cables that attach something like a keyboard or external device to a computer. That might be a solution for some people who wish to used digitalized equipment on their bikes.

 

[FurryOnTheInside]

I have read through this thread a few times and perhaps because I have little/no understanding of electronics I still have no idea which type of wire I need!
Is the kit wire (not cap) inherently bad or poor quality? Is there a right and wrong type of wire to go with my NGK iridium plug and NGK non-resistor cap?

 

[crassius]

I like solid copper wire, but solid aluminum wire is OK too.

 

[butre]

the kit wire has poor quality insulation but the wire itself is decent enough.

 

[FurryOnTheInside]

Thanks guys. I will order a metre of copper wire off fleaBay (and keep the kit wire and cap together as spares).

 

[Steve Best]

there's resistance in the spark gap itself. if you run a correct wide spark gap then you don't need any resistor parts in your ignition system.

I have to disagree with this. There is a dielectric (insulation) voltage that the coil has to overcome before a spark will jump, but once current starts to flow there is no resistance. This causes a huge flow of current, which is really hard on electronic components. It also causes a sudden reverse current surge from the back EMF which spikes the CDI from the back direction, several times as the current surges back and forth on the un-resistored back EMF harmonic. Resistor wire and plugs dampen all of this.