Coil Quandry: 3 Ohms vs 5 Ohms

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Dr. Frankenstein
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Coil Quandry: 3 Ohms vs 5 Ohms

#1

Post by Dr. Frankenstein »

Do ohms make a difference in the GL1000? I'm at the stage where I need to start considering some new coils for my '78 GL1000, but Dynas are out of my reach, too expensive. Electricity is not my strong suit, so what difference would it make to use 5-ohm coils vs 3-ohm coils on a stock '78 GL1000? Is there anything out there that's plug-n-play? Is anybody using a good aftermarket coil?
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#2

Post by digger »

Sidecar Bob has an excellent post on using GL1500 coils. https://www.ngwclub.com/forum/viewtopic.php?f=1&t=60509
There are a few other posts on using GL1500 coils as well that you should read up on.
This is a winter project I will be undertaking on my 75 wing. I will be staying with points ignition by the way & not using a resistor per Mike Nixon’s recommendations as he has posted on ignitions.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#3

Post by Whiskerfish »

It would probably be a very minor difference in operation, and if it showed up anywhere it would be during the start sequence. The stock coils are called 3 ohm but most I have measured are actually about 2.5 ohm. The coils are wired in Parallel. In that configuration you divide their resistance in half. So a pair of 3 ohm coils is actually providing 1.5 ohms of resistance. You combine that with a Ballast of approximately 3 ohms and you come up to 4.5 or so ohm total system resistance. The ballast is there to reduce the ignition system current draw when the bike is running.

If this were mine with the 5 ohm coils I would bypass the Ballast (just connect the 2 wires at the end of the ballast to each other) and see how it fires. On the stock setup the ballast is bypassed when the starter button is pushed to provide a hotter spark to get the bike to fire up. As soon as the start button is released the ballast is back in the system to reduce the power draw and reduce the power through the points extending their life. So long as you do not have any extra power demands on the charging system it should be fine. Lot of written on the subject here: https://www.randakksblog.com/ballast-re ... procedure/
and Here: https://www.ngwclub.com/forum/viewtopic ... 64#p246050
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#4

Post by Dr. Frankenstein »

Thanks Whiskerfish! Your description is probably the BEST description I have read about the part the ballast resistor plays in the ignition sequence, and all the rest of the information you wrote about in that NGW thread is very illuminating; I know there's been a lot of posts about the ballast resistor in here, but as I mentioned I'm not the sharpest knife in the drawer when it comes to electricity - "Power, Load Device and Ground" is about as far as I go, so that was very helpful to me.

So if I'm hunting new coils and plugs, 3 to 5 ohms is fine, and you recommend the DR8EIX plugs? That would be a good way to go on the stock '78 GL1000 system? FWIW, I have four new XD05F plug caps...

Honestly, I don't color outside the lines too much when it comes to bike renovation; I figure the original engineers knew way much more about what they were designing than I do when it comes to rebuilding these systems. I have a manual for each and every bike I have and usually stick to it religiously, so your insights are very helpful.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#5

Post by Whiskerfish »

Generally speaking one set of resisters is adequate. So if you have resister caps you should not need resister plugs.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#6

Post by pidjones »

Whiskerfish wrote: Wed Dec 29, 2021 10:15 pm Generally speaking one set of resisters is adequate. So if you have resister caps you should not need resister plugs.
Yes, and so many non-resistor plugs are becoming very hard to find (or, when found turn out to be China clones). Might be best to use non-resistor caps. Many NGK caps can have the resistors replaced by a piece of copper wire or tubing.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#7

Post by tlbranth »

I'd do as Whisker recommended. Bypass the resistor (not needed for decent modern coils). Use Dyna 5 ohm coils or if you can't afford them use GL1500 coils (I believe they are 5 ohm).
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#8

Post by digger »

Whiskerfish, thank you for the informative article on GL1000 ignitions, the time and effort you put into this is really appreciated. I have never read this article before. I now have this copied to a file I keep with my other service literature. Thank you and the others who do so much to keep NGW club up and running.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#9

Post by Whiskerfish »

tumb2 tumb2 tumb2 tumb2 tumb2
"Agreement is not a requirement for Respect" CDR Michael Smith USN (Ret) 2017
"The book is wrong, this whole Conclusion is Fallacious" River Tam
2008 GL1800 IIIA "TH3DOG"
1975/6/7/8/9 Arthur Fulmer Dressed Road bike
1975 Naked Noisy and Nasty in town bike
and a whole garage full of possibilities!!

Psst. oh and by the way CHANGE YOUR BELTS!!!!
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#10

Post by ericheath »

GL1200 and 1500 and many mid 80 Honda bikes are 3 ohm coils. I believe the lower the ohm, the faster the coil can develop a charge. (Saturation/ Dwell time) Maybe it also increased voltage, can’t remember. The 80-81 1100 coils were very low ohm coils. They increased them a bit in 82-83 I think, and added a ballast again. Lower ohms might help at higher rpm as saturation time gets shorter.

That said, I’ve run stock points and coils, Dyna ignition and stock coils, Dyna and Accell coils, Dyna and gl1500 coils. And I had the optical system like C5 with section and bobbin coils with three sparks for event.

At higher speeds, I couldn’t tell any difference. Butt Dyno only. Starting was better with C5. But properly adjusted, the others were all great. Points of course required more maintenance and were more difficult to get set properly. Setting the C5 was by far the easiest.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#11

Post by Don R »

I run a dyna, no ballast resistor and 1500 coils. I think I used a combination of 1500 and 1978 brackets to mount them.
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Re: Coil Quandry: 3 Ohms vs 5 Ohms

#12

Post by Sidecar Bob »

Whiskerfish wrote: Wed Dec 29, 2021 7:42 am The coils are wired in Parallel. In that configuration you divide their resistance in half.
Not quite. They both get power from the same place but each coil finds ground through its own set of points (or module in the Dyna S or similar) so current should not pass through both at the same time.

My write up linked above is about using the GL1500 coils with a Dyna S in an '83 frame so the part about the bracket won't apply to your 1000 but everything else is the same and I did post links about doing the same thing in a 1000 frame.
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