4 ohm vs 3 ohm coils

[uteman]

The shop manual that I have for 1980 GS850 with transistorized ignition advises a coil resistance of "About 4 ohms"
I will check mine tomorrow.
Many after-market coils advertised are 3 ohm.
What is benefit (if any)?

The price variation for after-market coils is huge.
I am aware that one gets what one pays for but I would like to hear readers experience and recommendations.
The bike has original coils from 1980

 

[Chuck78]

The 77 750 coils I'm replacing now with Dyna 3 ohm green coils had measured out at 4 ohms... I thought that was curious...
And the generic Dyna instructions say to use 5 ohm coils...or 3 ohm coils with ballast resistors added?????
3 ohm has always been the standard or so I thought.

 

[Steve]

The resistance of the coils will determine how much current flows through them. The amount of current that flows through the coils determines the strength of the magnetic field in the core. The strength of the magnetic field in the core determines the strength of the spark when that field collapses. Most of the earlier coils are spec'ed at 5 ohms because the 2.5-3 amps of current that would flow is about the limit that points can handle without arcing too much when they are opened to create the spark. With transistors replacing the points in the bikes with electronic ignition (Suzuki's 'ignitor'), they could handle more current, so 3 ohm coils were spec'ed, which would run close to 5 amps of current.

Your '80 850 has electronic ignition, so it will handle 3 ohm coils just fine. It will handle 4, 5, even 10 ohm coils, if they even exist. The difference is that the spark will be better with the lower-ohm coils.

.

 

[uteman]

Steve (GS Whisperer):
Many thanks for your informative reply re coils.
Do you have any comments as to coils to purchase given the wide range of prices?

 

[Steve]

As far as brands go, you probably have about the same selection that we do, given the accessability of the interwebs, but I think the overwhelming favorite here is Dyna, with the green 3-ohm coils. My wife's bike came to us with Accel coils, they have done very well. Even the stock coils do well (until they fail).

.

 

[Sam 78 GS750]

Accel and Dyna seem to be the most highly regarded. I've personally used Accel on a couple of old UJMs (GS and Honda CB), and have always been pleased with the quality, performance, and reliability

 

[posplayr]

Accel and Dyna seem to be the most highly regarded. I've personally used Accel on a couple of old UJMs (GS and Honda CB), and have always been pleased with the quality, performance, and reliability

I like the accel coils as well.

These are for a Honda but looks similar

https://www.ebay.com/i/401535393815?chn=ps

 

[uteman]

I have a friends bike here also that needs new plug leads as they are stiff as a plank. Can the old ones be removed from coils?

 

[Nessism]

I have a friends bike here also that needs new plug leads as they are stiff as a plank. Can the old ones be removed from coils?

Yes. There are many older threads discussing how to do so.