Dual coil resistance - I think the manual is wrong

[dogbunny]

On page 184 of my Clymer manual there is a DIAGRAM that shows how to test the SECONDARY resistance of the dual-tower coils that were used from 1980 - on. In the diagram, the test is performed with the plug caps ON. The text says:

"Measure the coil secondary resistance between both PRIMARY () leads. The secondary winding resistance should be 10,500 - 15,500 ohms."

Okay, the word "primary" has to be an obvious typo.

But, here's the real question: I have several 1980 and later dual-tower coils. If I remove the plug caps and preform the secondary test, I get about 12,500 ohms on every one, which is right in the middle of the specs. That is with the caps OFF. The diagram on page 184 shows the caps ON when performing the secondary test.

Each of the caps on the dual-tower coils is about 9-10,000 ohms, so, if I measure the secondary with the caps on, I get about 30-33,000 ohms.

I am pretty sure my coils and caps are good, I just think the manual is misleading. Can someone please clarify this issue for me? I am very close to firing up my first TCI engine, and I would really appreciate your responses. Thanks.

[pamcopete]

dogbunny,

I believe that the original stock plug caps were not resistor caps and they were molded on. Perhaps your caps are aftermarket (NGK's?) with resistance. In any event, about 12,000 Ohms for the secondary is correct without caps or with non resistor caps.

However, those caps are a bit high in resistance, which is typically what happens to resistor caps over time. They should be 5 to 7K.

[dogbunny]

pamcopete, thanks for the response.

I was just about to post a follow-up question about the resistance of original equipment single-tower caps versus dual-tower caps. I have several of each. The caps that were on single-tower coils all read about 5K. The caps that were on dual-tower coils are all about 9-10K. My question is: were different caps specified for the different coils?

I think I already pretty much have pamcopete's answer which I greatly appreciate, but I would like to hear from others.

BTW, before I got into all these specifics, I did conduct a spark test on this TCI, dual-coil bike that I am working on, and I did get what appeared to be a good spark. That was with a coil that read 33K from cap-to-cap. That was 12.5K for the coil with an added 10K for each cap.

I have enough info to proceed with my project, but I would REALLY like to know what is supposed to be what. Thanks.

[dogbunny]

Okay, one more update.
I performed another spark test, this time with 5K caps, so the total cap-to-cap resistance was about 22.5K ohms. The spark looked a whole lot better than when I had the 10K caps on with the total cap-to-cap resistance of 33K. The spark now had some blue in it, whereas before it was totally orange.

But, I would still like to please hear from others about what should be what.