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Since there is no battery and no rectifier all voltage on your bike is AC. Why do you ask?
 

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Discussion Starter #3
Is the cdi ac or dc?
Since there is no battery and no rectifier all voltage on your bike is AC. Why do you ask?
Just got this bike and someone made a mess of all the wiring there's only five wires going to CDI Googling it says different things so I wasn't sure now if it's AC or DC I thought someone left one of the wires out because it has six pins and only five wires going to it
 

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Just got this bike and someone made a mess of all the wiring there's only five wires going to CDI Googling it says different things so I wasn't sure now if it's AC or DC I thought someone left one of the wires out because it has six pins and only five wires going to it
Here you go
42461
 

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I got new stater coming and the wires are different color too but 1 of them is a male single plug and the other 3 are female
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Looks like a home made connector bodge-up , but if you have a look at the wiring diagram you can see that the Black/White male connector is the Black/Red male connector on the diagram, the other wires are correct and should have plugged straight into the CDI, do you have the workshop manual?
 

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No and the pigtail from to the cdi box is missing. It was just hard wired to everything. If i knew what these 2 wires from each of these did i could figure it out. Does only 1 of these wires generate 12V?
42464
 

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Wow. You were not kidding when you said someone made a mess of the wiring. Just to clarify what I said earlier about AC voltage. The magneto output to the CDI is AC, however the CDI unit may convert the voltage internally to DC for your ignition coil. I am unsure though as I have heard of some CDI units that use AC to charge the ignition coil. Ropp do you know for sure what method this KX uses?
 

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Interesting. Well in that explanation it is very clear that the diode within the CDI is converting AC to DC but since a diode can only remove one half of the AC sine wave, it will provide pulsed (half wave) DC voltage.

The example Ropp provided is for an ignition system with an alternator but the KX diagram shows a magneto instead of an alternator. This begs the question of what is the difference between an alternator and a magneto and here is were it gets clear as mud. Various sources define them differently. Some say the only difference is that the magneto uses permanent magnets and the alternator does not. This explanation makes sense to me since the word magnet is in the word magneto. But other sources say the difference between a magneto and an alternator is whether the magnets rotate or are stationary. I tend to discount that explanation. Getting back to the point. Since both produce AC, I figure Ropp's example is helpful in understanding how CDI works on either system.

At any rate, we know the KX has a magneto and it has permanent magnets in the flywheel, so the magnets rotate.

To get back to the real problem, I would hope that when the new stator arrives it will have detailed instructions that will help with wiring.
 

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Another spanner in the works about AC and DC CDI's, found this ,another interesting video, the KX250 has a stop button
 

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Hey Ronzzzz,

How certain are you that your KX is a 1988? The reason I ask is because the CDI box in your photos is not from a 1988 KX250. From 1974 right up until 1997, all KX250 CDI boxes used wire pigtails instead of the embedded connectors shown on your photos. I think somebody swapped out your original CDI and replaced it with a much newer one because original one are no longer available.

In order to wire it correctly, we will have to figure out what year and what model the new one came from. Are there any part numbers on the box?
 

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Discussion Starter #15
Awesome thanks. I noticed it does have a kill switch and the idiot who botched this up left that wire off of the cdi box. Luckly i did order the correct ac cdi box. Now i just got to find a pigtail to make it all good 👍
 

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Discussion Starter #16
42502
The guy said its a 1987. I googled vin number and it came out to be a 1988 model this is the new one i ordered.
 

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Looks good. Do you have enough information to make all the right connections now? Has the stator arrived yet? How about some bike pix? Would love to hear this puppy run when you get it going.
 

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I think i got this👍 ill put pics up later on bike. I still need do compression test. May need top end rebuild also. Thanx. Ill keep updated. Luv the older bikes.
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I bought a 1979 KX250 brand new. They were air cooled back then.
I raced it for one season. The bike was good; The rider not so much. 😁
But I had fun.

Good luck with your restoration.
 

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Lol thanks. My last one was a 03 kx250. Long story but i luv getting airborne with the bike ahead of me. Ouch. Lesson learned. Dont ever make a ramp out of flexable sheet metal😬
 
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