upgrade plugs with dyna 3 ohm coils?

Hey guys, let me start out by saying I did try the search bar. I don't know if I used the right phrases or not but I found nothing on this.

My question is: my bike has dyna s ignition, dyna green 3 ohm coils, and 8mm plug wires. I read a while back about a different spark plug and a larger gap setting for the hotter coils, but can't seem to remember where I read it. Does anyone have any if on this? The other mods are Kerker 4 into 1 headers, jetted stock carbs, pod filters.

Some places recommend a little wider gap for CDI because it can make a higher voltage than stock. However, widening the gap doesn't change the amount of energy stored in the coil during the "ON" cycle which is what limits spark energy. I have run CDI for over 30 years on my 750 and I just use the max stock gap which is 8mm (.032").

But to be clear: increasing gap distance increases the voltage at which the E field ionizes the air and allows the spark to jump. That means the coil voltage goes up higher before spark firing which stresses the coil more. I don't know if it improves performance, I have never seen any evidence that it does.

Thanks for the quick reply! So based off of that I should still use the stock spark plugs and keep the 8mm gap? I really don't want to stress out the coils as they're not cheap lOl. I think the other number that was suggested was b8ea as opposed to the b7ea stock plug.

78kz650guy wrote: Thanks for the quick reply! So based off of that I should still use the stock spark plugs and keep the 8mm gap?.

That's what I have run for the last 30+ years.

Then that's the plan! Thank you!

8mm gap sounds a little big. :laugh:

Some say a larger gap gives a little more zing to the motor, and I thought I was imagining it, but it did feel more emphatic with the wider gap. But because it really stresses out the parts, and likely shortens their life, I would say run the stock gap as long as the bike is running well.

Keep an eye on your charging voltage when you change to the 3 ohm coils. They use more power, and some people with 78/79 Kz650's have had some charging issues with the Dyna S and 3 ohm coils. (Converting to 3-phase charging system usually cures that.)