Can CDI's Partially Fail

Moshman · Two Stroke Sniffer Joined: 22 Mar 2006 Karma :

My GPZ1000 still won't start. I have checked coils they are fine, i have checked pulser coils they are fine.

I am getting no negative feed to one of the coils. This is fed straight from the CDI it does keep powering up every so often.
The other coil is getting feed and is sparking everytime. I have had the multimeter on the positive feed to the coil and on the wire as it leaves the CDI and there is no voltage there unless i engage starter then it goes up to 15V then drops straight to zero.

My question is can a CDI partially fail, ie supply one coil and not the other. I was always under the impression a CDI unit either works or does'nt.

Any input would be greatfully received as the weather is getting better but my bike isn't.

Moshman · Two Stroke Sniffer Joined: 22 Mar 2006 Karma :

Does anybody know of anywhere near Chesterfield that can test my CDI

iCraig · World Chat Champion Joined: 05 Jun 2004 Karma :

Rather than the CDI sounds like a short or a bad connection to me somewhere.

bish777 · World Chat Champion Joined: 11 Nov 2004 Karma :

check the earth from the coil. Put the negative terminal direct to ground and see if it works.
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GSXR1100J

Moshman · Two Stroke Sniffer Joined: 22 Mar 2006 Karma :

Its the earth to the coil that is suspect. But goes straight from the CDI to the coil. If i put it straight to ground and it sparks does that mean my CDI is faulty

fatboyslim · Derestricted Danger Joined: 20 Feb 2006 Karma :

finpos · World Chat Champion Joined: 13 Sep 2005 Karma :

Assuming you have two coils and two pickups, then what is inside your cdi box is actually two cdis in a single package. So, yes, one half of it can fail.

The "earth" wires between the coil and cdi are actually trigger wires - in normal operation they will be pulsing 12V-Earth every time the pickup reaches it's firing point, and it's this pulse which will cause the coil to spark. By grounding this wire, you are essentially simulating one pulse. So if you get a spark out of the plug when doing that, it should give you (some) confidence that the coil itself is ok - BUT it may still have a problem in normal operation if it cannot recover quickly enough to make the next spark.

The easiest thing for you to do is to swap over the two trigger wires between the coils and the cdis. if the fault then also swaps betweem coils, then the cdi or pickup for that side is burst (try swapping pickups next). If the fault stays on the same coil, the fault is with the coil or associated wiring gubbins.

If you do this, remember you are also trying to eliminate a problem in the trigger wires, so don't feel scared to run a couple of extra wires in parallel between the cdi and coil.

finpos.

Moshman · Two Stroke Sniffer Joined: 22 Mar 2006 Karma :

Thanks folks i will investigate at the weekend.