Ignition Coils

[Syd]

Hi Folks

1980 GS 1000 G

I'm at the point in my bike rebuild where I'm checking/installing the electrics. I tend to check and inspect as much as possible 'on the bench' before installation.

After the wiring loom installation it is time to check/install the ignition coils. So I've checked the impedance values in my manual and it states...

Primary - 3 to 5 ohms.
Secondary - 31 to 33 K-ohms.

The numbers for Primary I'm getting are - both coils showing 3.8 ohms (Nice)

The numbers for Secondary are - Left coil 11.9K ohm and Right coil 0.0K ohm. OK, so the left looks low and the right, well, dead.

Test performed with plug caps on and off, same readings.

First things first. Search GSR Forum for any information coil related. From what I can gather, it appears the thing to ensure, is replacement coils meet the factory spec impedance as there may be risk of damage to the TDI unit.

I note on the forum the mention of Dynatek 3 or 5 ohm coils. Unfortunately for me, the cost is prohibitive due to exchange rates, shipping and Australian additional taxes.

So it's off to an interweb search to find replacements.

Iv'e found an eBay seller here in Australia that I've purchased from before. They have coils listed specifically for the 1980/81 GS1000G that fit my budget. Their listing shows the impedance as - Primary 5.11 ohm and Secondary 17.55K ohm. Those numbers look odd considering the information in the workshop manual.

OK that's the ramble, now the question.

Is 5.11 ohm for Primary a bit on the high side and 17.55K ohm considered too low? What I am not clear on, is which side of the coil could cause damage to the TDI if the impedance is not satisfactory.

Any advice would be greatly valued.

[unfocused]

I have a 78 GS1000 engine mounted in a 77 GS750 frame using the original GS750 wiring harness:

In my case I run an after market electronic ignition. To prevent any issues, I researched and went with 95 Katana style coils that are 4.3 ohm.
I've noticed an improvement with my charging system and the engine runs well. I also installed a relay for direct battery voltage to my ignition system so I don't pull my power from the wiring harness. The original power source for the ignition is now my switch wire for the relay.

[Grimly]

Fit a pair of Honda MT-08 coils and be done with it.

[rphillips]

Thinking Suzuki coils are pretty solid. I've rarely heard them even mentioned. I'd hate to replace one with only 44 yrs. service, must have been a problem with materials or workmanship.

[Syd]

I have a 78 GS1000 engine mounted in a 77 GS750 frame using the original GS750 wiring harness:

In my case I run an after market electronic ignition. To prevent any issues, I researched and went with 95 Katana style coils that are 4.3 ohm.
I've noticed an improvement with my charging system and the engine runs well. I also installed a relay for direct battery voltage to my ignition system so I don't pull my power from the wiring harness. The original power source for the ignition is now my switch wire for the relay.

Thanks for the info regarding '95 Katana style coils. I've been looking into this as a viable option although I do not have an after market electronic ignition system (yet).

Do you know if these coils would be suitable as a direct replacement with the stock TDI system?

[grcamna2]

I'm having a similar issue on my 81' GS450.

I want to be sure that replacement coils have the same impedance(3-5ohms?)as my stock coils.

[unfocused]

Thanks for the info regarding '95 Katana style coils. I've been looking into this as a viable option although I do not have an after market electronic ignition system (yet).

Do you know if these coils would be suitable as a direct replacement with the stock TDI system?

I can only imagine yes. However, I am not familiar with the TDI system.
One other option I have interest in is the coils from a DT115 outboard engine.
Reasoning: I can have all four coils fire with the same polarity and have the coils on the same side of the engine as the cylinder

[Forden]

Are these impedance specs (Primary - 3 to 5 ohms. Secondary - 31 to 33 K-ohms.) the same for a '78 GS750E? My service manual doesn't seem to list them, only advises to use an "electro tester" to measure spark distance... Didn't find the resistance spec in Clymer either.

Thanks.

[tom203]

With plug caps removed, over the secondary will yield about 13kohm….plug wire to plug wire. With installed caps of 10kohm each, cap to cap will yield cap to cap 33kohm. If you use the more common 5kohm plug cap, you’ll get about 23kohm cap to cap.