Technical coil question

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moizeau
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Technical coil question

Post by moizeau »

Looking for some advise and knowledge please.
I've recently bought a 1980 Kwak Z650 (because I don't have a moped). One coil is dead i think. It's got a very weak spark, as in you get a tingle when holding the plug not a smack. I've swapped the the 2 coils over to take the points and condenser out of the equation and the issue stays with the coil, checked it's earth, swapped plugs etc. etc. I've measured the primary winding, it should be around 4 ohms but is 5.8. I'm 99% sure it's dead but before I find another I want to be absolutely sure. I have another 3 bikes, all Kwak, 1 thou and 2 1100's. One is in bits, the GPZ11 Injection, so I can borrow a coil from that without dismantling one of the others. The problem I've got is that the other coils are TCI coils I think because very few bikes are true CDI. The primary and secondary windings are, however, rated much lower. The Z650 should be 4 ohms and 23 K ohms, the GPZ is 1.8 - 2.8 and 10.4 - 15.6 K according to the books. It's very easy to swap it in but I don't want to kill a good coil. I know I can use the Z650 coils in a TCI set up without issue but can't find any info about going the other way round (because no one goes backwards).
Can anyone see any issue if I do this?
Cheers
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xantia_v6
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Re: Technical coil question

Post by xantia_v6 »

I think that there is little danger of damaging a coil, as the secondary voltage is limited by the spark gap in the plug. CDI systems heat the coils less because the spark pulse is much shorter, but the instantaneous current is greater.

Although you are measuring a primary resistance out of spec, it is more likely that the coil has a partial short circuit in the secondary that only breaks down with high voltage and can't be measured statically.
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moizeau
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Re: Technical coil question

Post by moizeau »

Thanks, I'll give it a go then
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moizeau
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Re: Technical coil question

Post by moizeau »

Thanks again, just tried it with GPZ11 coil, started straight up.
Cheers