1983 GS850G - Changing Ignition Coil Primary Resistance - Will this create problems?

[OldVintage]

Hey guys,

I picked up a 1983 Suzuki GS850G about 9 months ago. This is my first project bike and I've been slowly going through the various systems on the bike and replacing, updating, fixing, modifying as needed. I'm going through the electrical system right now. I'd like to replace the ignition coils as part of a broader complete wiring overhaul. I had my eye on the Dynatek coils, but noticed they don't have any coils with 4 Ohm primary resistance, but they have dual output coils in 3 Ohm and 5 Ohm. I couldn't find anything about tolerances on the primary resistance. The manual I have just says "about 4 Ohms".

Question 1: Has anyone had any success changing the stock coils to Dynatek 3 Ohm or Dynatek 5 Ohm dual output coils? Should I be concerned about changing the primary resistance? Could other sub-systems or components be negatively impacted by this change?

Question 2: Are there other replacement coils that have 4 Ohm dual output coils out there without fixed spark plug cables? So far I've only come across 4 Ohm coils with fixed cables.

Thanks for the help!

 

[Steve]

Get the green 3Ω coils and enjoy the ride.

I think the manual actually specifies 3-5Ω coils, so you're good.

.

 

[Grimly]

The standard electronic ignition coil is around the 3 ohm mark, so it should be ok. There is a much cheaper option, though.

Honda and Kawasaki both used replaceable-wire twin-output coils, that can be picked up for a song on ebay.
I recently got a triple set from a Gold Wing, averaging 8 dollars per coil, plus shipping.
They're 3-ohm MP08 type number. Dead reliable and fitted to literally dozens of Honda models over the years.
I've been using these Honda coils for years now and don't have any negative opinions of them.

 

[OldVintage]

The standard electronic ignition coil is around the 3 ohm mark, so it should be ok. There is a much cheaper option, though.

Honda and Kawasaki both used replaceable-wire twin-output coils, that can be picked up for a song on ebay.
I recently got a triple set from a Gold Wing, averaging 8 dollars per coil, plus shipping.
They're 3-ohm MP08 type number. Dead reliable and fitted to literally dozens of Honda models over the years.
I've been using these Honda coils for years now and don't have any negative opinions of them.
View attachment 59927

The standard coil is 4.3 Ohm from what I've found in the manuals and for replacement parts online. I also measured both of the original ones and measured around the same, between 4-4.3 Ohm. For some of the GT models it calls out 3-5 Ohms, so I figured I could probably go down to 3 Ohm and still be ok. I might pick up some of those Honda ones and give it try. Have you ever checked the temp on them when you get run high RPM?

 

[Brendan W]

Is there something wrong with the old coils?

 

[OldVintage]

Is there something wrong with the old coils?

Not that I could tell. I measured primary resistance on both and they seemed fine. Both were between 4 and 4.3 Ohms. Aside from wanting to replace coils that are 30+ years old, I'm interested in swapping to replaceable-wire coils to replace the spark plug wire with colored options that better fit the overall color scheme. It's not something that's really necessary in the grand scheme of things, but figured if I'm doing a whole electrical overhaul I might as well include the coils in there too.

 

[Rijko]

The standard electronic ignition coil is around the 3 ohm mark, so it should be ok. There is a much cheaper option, though.

Honda and Kawasaki both used replaceable-wire twin-output coils, that can be picked up for a song on ebay.
I recently got a triple set from a Gold Wing, averaging 8 dollars per coil, plus shipping.
They're 3-ohm MP08 type number. Dead reliable and fitted to literally dozens of Honda models over the years.
I've been using these Honda coils for years now and don't have any negative opinions of them.

Very interesting, had not heard this before.
Seems a cheap and good alternative for the 3-Ohm Dyna or Accel coils.

Also, the fact the cables are replaceable is something i like a lot.
( Anyone ever watched in a dark garage the sparklets crawl on the 40-years old cable ? )

How do these fit to the standard GS mountpoints ?

 

[Grimly]

How do these fit to the standard GS mountpoints ?

They're about 10mm short, so all I do is fasten the front hole as normal and fasten the rear one trapped with a couple of washers. Rock-steady fixing.

 

[Grimly]

The standard coil is 4.3 Ohm from what I've found in the manuals and for replacement parts online. I also measured both of the original ones and measured around the same, between 4-4.3 Ohm. For some of the GT models it calls out 3-5 Ohms, so I figured I could probably go down to 3 Ohm and still be ok. I might pick up some of those Honda ones and give it try. Have you ever checked the temp on them when you get run high RPM?

There's some variation, all right. I've generally found the contact-breaker coils to be 4ohm primary and the electronic ignitor coils to be around 3ohm.
Checking in the Haynes Book of Lies, they say they're both the same at 4ohms, but the secondaries differ - the CB secondaries are 15Kohms and the Electronic secondaries are 32Kohms. That would suggest that using CB coils on an electronic ignitor would work, but the spark would be weaker.
Whatever.... anyway, the Honda coils test out around 3ohms primary and around 12Kohms secondary, so <shrug> and they produce a decent spark; they've been stone-reliable, and are currently sporting a set of Sooper-Dooper Hi-Perf blue silicone leads, from a World Champ F1 Team..... <cough> nah, a Hyster fork truck. It took some believing that Hyster were fitting their fork trucks with $300 leads (full retail price). Found them brand-new in box at a swap meet kind of affair. Had to slim them slightly to fit, as they're 8mm thick, and my reluctance to chop the end caps off means that I'm now running resistor plugs. It all works quite well, really.
Can't say I've checked the temps - they're not exactly accessible.

Just as a reference; here is the MP08, and what it's fitted to...
https://www.partzilla.com/product/honda/30510-KT7-013?ref=a758cc579013d398ac98144e983bc79033a2d77e

 

[bwringer]

I've only had the three ohm green Dyna coils on my '83 GS850G for, oh, about 120,000 miles... stock ignition, too.

Not to be hasty, but I think it's working out OK.


Note yellow and orange Accel ignition wires. I picked up a V8 set super cheap from the discount table at Advance Auto about 15 years ago missing a coil wire I didn't need. Still got the other four on the shelf just in case: