What killed my CDI coil assembly?

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Jordan
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Joined: Fri Dec 24, 2010 11:29 am

What killed my CDI coil assembly?

Postby Jordan » Fri Jul 13, 2018 12:07 am

I bought and fitted to my Ducati widecase a CDI coil unit made for for an Indian Vespa clone.
It is a pocket-friendly alternative to the original, with identical mounting and wiring details.
This worked well for a while, then suddenly stopped.
I replaced it with an identical unit that I bought at the same time - running OK at present.

What might have caused the Indian CDI unit to fail?
I'm wondering if the Motoplat trigger coil might be producing too much voltage, and whether an added resistor might help?
Any thoughts before I try this?

Of course, it may just be that it was a faulty unit.

graeme
Posts: 593
Joined: Sun Mar 25, 2012 12:00 am
Location: Australia

Re: What killed my CDI coil assembly?

Postby graeme » Fri Jul 13, 2018 10:18 am

“What might have caused the Indian CDI unit to fail?“

Curry? Cheapness?

Jordan
Posts: 795
Joined: Fri Dec 24, 2010 11:29 am

Re: What killed my CDI coil assembly?

Postby Jordan » Fri Jul 13, 2018 10:37 am

Hang on, are you suggesting Ducati electrics are superior quality? :)

I'm interested in the technical reason for the failure.

ecurbruce
Posts: 286
Joined: Fri Apr 01, 2011 12:43 am
Location: Lakeland fl

Re: What killed my CDI coil assembly?

Postby ecurbruce » Fri Jul 13, 2018 5:01 pm

Inductor coil

Hi Jordan,
Since no-one else has replied, I'll jump right in with my two cents worth...

Can you measure the current coming from the motoplat inductor coil? And can you get a data sheet for the cdi unit you have from the www?
When I was designing my electronic ignition, I found that the inductor coil associated with the GM electronic ignition unit would not function at all with my denso ignition module, because of a difference in inductor current output...
If your inductor coil current is too high for the cdi unit, probably a resistor will work, but which one? Maybe Hans will chime in here and tell you which one.
However since your setup was functioning for a period of time before failure, and the replacement is also working, I'm GUESSING- they are a workable match. Also, I'm guessing time will tell...
Again guessing, I'd be leaning toward cdi unit failure until the next failure.

Bruce

Ventodue
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Joined: Mon Mar 08, 2010 3:23 pm
Location: Montpellier, France

Re: What killed my CDI coil assembly?

Postby Ventodue » Fri Jul 13, 2018 6:11 pm

Well, until you've had at least two fail in similar circumstances :D , Jordan, the betting would have to be on it being simply 'a faulty component from new' in the unit - i.e. nothing necessarily connected (ha, ha) to your particular circumstance ...

Craig, waiting for news of a second failure .... :D :D :twisted:

P.s A mate of mine recently went thru 3 solenoids for his Aprilia Falco. It was only then that the supplier discovered the whole batch was faulty ..

Jordan
Posts: 795
Joined: Fri Dec 24, 2010 11:29 am

Re: What killed my CDI coil assembly?

Postby Jordan » Fri Jul 13, 2018 10:08 pm

Bruce:
I think I could measure the current from the inductor, if by that you mean the trigger coil.
But it would be a big, off-bike job. Adding a resistor would be easier, but as you say - how much resistance?

Craig:
Your suggestion to see if the second unit also fails is scientific, and not outrageously expensive.
These Indian CDI units cost pocket money.

Thanks for the thoughts, gents.

ranton_rambler
Posts: 155
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: What killed my CDI coil assembly?

Postby ranton_rambler » Sat Jul 14, 2018 8:51 am

I'm not an electronic engineer, but I do get involved in electronic components via my job. I can tell you that although there are no moving parts in electronic boxes, so you would not expect them to wear out, they can fail due to heat and vibration. There is also the chance of manufacturing defects which don't get picked up before they are shipped out. Good manufacturers do more testing to stop these kind of defects getting out, some others may not.
A couple of examples I have seen:
PCB "washcoat" during manufacture not correctly formulated so flow solder did not work properly. Intermittent drop-outs of power in use. That needed forensic examination of failed PCB's to find it once we'd seen enough failures to get a bit of a pattern.
Thermal expansion in use caused potting compound to expand. This stressed the legs of a component soldered to a PCB and eventually cracked them through fatigue.

Jordan
Posts: 795
Joined: Fri Dec 24, 2010 11:29 am

Re: What killed my CDI coil assembly?

Postby Jordan » Sat Jul 14, 2018 10:05 pm

Electrics: Italian designed, made in India. What could possibly go wrong?


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