Alternative coils

[Nails]

It chaps my hide that there are no new coils to fit XIIs. God knows, I wouldn't put a used coil in my 1980 GMC pickup! (But I might've stuck in one from an even older Scout.)

First off, for the purposes of this discussion, let's just kinda pretend that I have no earthy idea what I'm talking about with this electrical mambo-jumbo. Okay?

In reality, I have the vast experience of once putting a Nology coil in a thumper, which (I'd like to say) practically doubled the engine's output. But I don't so much like to say that actually the bike ran just like normal, exactly as everybody said it would. So I put "racing" (below) in quotes. In this post, I'm just going for the availability/reliability of a new coil.

Back to the XII. I notice that our coils have a spec of 1.8 - 2.8 ohm in the primary winding ... like basically every other motorcycle "of a certain age" (read "points"). I also notice a lot of coils advertised for other bikes, like say a CB900, look an awful lot like the coils in my XII. They're cheap and surely Chinese, with different threading on the connectors and dubious quality, but I digress. I'm going for quality/reliability here.

I also notice that Dynatek makes a "racing" 3 ohm coil which immediately raises the question, "What's the worse that could happen?" That, in turn, immediately-er raises the answer: "You could fry the igniter."

Back to the coil, I understand that the slightly higher primary resistance (3 ohm instead of about 2.5 ohm) would just result in a higher spark voltage. But my question is, what are the chances that the igniter couldn't abide? (This is another low-risk, high-hazard decision -- slim chance but igniters are pricey.)

Please phrase your replies in simple language for the benefit of others who might not be hip to this electrical mambo-jumbo. Okay?

[Edit: of course, just after posting this, I found a Dynatek 2.2 ohm coil set: https://www.denniskirk.com/dynatek/2-2- ... 200459.sku. Pricey, but worth it to me for reliability. I don't see the primary connectors, and would need to put real (male) ends on the sparkplug wires.]

[SgtSlag]

To achieve maximum power transfer, the two 'ends' have to have nearly equal impedance/resistance, so the closer you are to the specified range, the better. The 2.2 Ohm coil is near ideal (2.5 Ohm), well within the range specified by Kawi. It should be good.

My 1979 Honda CB750K had old, weak, OEM coils. New coils were pricey, so I went for NGK Iridium spark plugs, hoping for the best...

Normally, I had to grind the starter, 4-6 seconds, rest, then grind again, to get the Honda to start. After I installed the new plugs, I hit the button, and the bike was running!!! I literally jumped in surprise!

I went the same route with my XII: no issues starting it, but I wanted some insurance on the ignition system. They're around $10/plug, but that is very affordable insurance.

They've been installed for 11 years, 30,000 miles, without issue. Cheers!

[Mega-Hertz]

ha! i just went through this.
I couldn't find anything OEM for "Lamont" (my bikes first name). so i went with some chinisesum GSXR1100 coils. they work real good.
i can't help but think about, that maybe the LED head lamp i replaced the OEM with sped up the death of my coils.

[SgtSlag]

Coils are high energy, high voltage, high stress components; the engine vibrates, and over time, all of these elements lead to the insulating varnish on the coil's windings to break down, leading to failure. In other words, nothing lasts forever, and the harsh environmental conditions these parts live in, leads to failures.

Back in the early 1970's, everyone loved to bash the cheap Japanese electronics they were buying. Today, everyone loves to trash the, "cheap Chinese crap," they buy on the markets. The Japanese electronics were not really that low in quality, and I don't think the Chinese stuff is as terrible as everyone likes to say they are, either. Cheers!

[cushman eagle]

I looked on Partzilla yesterday and they list the coils as pt#21121 and 21121A for $135.49 each,I did not check for availability