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Old 10-25-2007, 05:41 PM   #1
cwc OP
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Suzuki Ignition/CDI/Stator question

After spending a week in Ciudad Chihuahua waiting for a stator for my 1995 DR350 it occurred to me that I should maybe be prepared for such and eventuality.

The failure on the stator was the winding that provides power to the CDI. Apparently this is not all that uncommon.

I bought a spare CDI and coil, but I don't want to carry a spare stator.

I took some measurements and discovered that the power supply to the CDI was roughly a 20v peak-to-peak square wave and the output of one phase of the charging circuit was roughly a 30 volt p-p square wave.

It occurred to me that I might be able to use the signal from the charging circuit through an isolation device such as a transformer to drive the CDI in a pinch. The current required appears to be about 50ma. peak so there isn't a lot of power there.

Has anyone tried to jury rig something like this?

Does anyone have a schematic so I can see exactly what is going on inside the CDI and/or regulator rectifier?
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Old 10-25-2007, 08:29 PM   #2
strongbad
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As you pointed out, the CDI is a very low-power load for the stator, so I'm very surprised that this one winding failed. How did you determine that the winding is bad?

I would never buy a new stator. I'm comfortable with re-winding them. On the rare occasion when a stator fails, it's the copper winding that fails, so why not save yourself a ton of money and just re-wind it? Magnet wire is cheap and plentiful. Any place that repairs electric motors will usually sell you magnet wire.

I'm very skeptical that your stator is bad. But if it's really bad, just re-wind that one CDI winding. Simple.

About an alternate way of powering the CDI: the CDI needs DC ultimately to work. It takes the AC from the stator winding, rectifies it to DC, filters it, then regulates it. Rather than trying to find another AC source for it, try a DC source. It may work fine with 12VDC. If the CDI input is a full-wave rectifier, the polarity doesn't matter. If the CDI input is a half-wave rectifier, apply the DC one way and see if it works and if not, try reversing the wires.

The only reason the CDI has it's own winding is so that the ignition will work with a dead battery.
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Old 10-25-2007, 10:17 PM   #3
cwc OP
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Thanks for the reply.

Quote:
Originally Posted by strongbad
As you pointed out, the CDI is a very low-power load for the stator, so I'm very surprised that this one winding failed. How did you determine that the winding is bad?

It had no output and the coil was open. A new to me stator made it run.

I would never buy a new stator. I'm comfortable with re-winding them. On the rare occasion when a stator fails, it's the copper winding that fails, so why not save yourself a ton of money and just re-wind it? Magnet wire is cheap and plentiful. Any place that repairs electric motors will usually sell you magnet wire.

I did save the old stator and may rewind it. I have some experience doing that and a good selection of magnet wire.

What do you use to replace the goop that Suzuki uses to keep the wires from vibrating and breaking where the coil ends connect to the wires that go out to the CDI?

I'm very skeptical that your stator is bad. But if it's really bad, just re-wind that one CDI winding. Simple.

Not when you are in Ciudad Chihuahua....or Tubares.

About an alternate way of powering the CDI: the CDI needs DC ultimately to work. It takes the AC from the stator winding, rectifies it to DC, filters it, then regulates it. Rather than trying to find another AC source for it, try a DC source. It may work fine with 12VDC. If the CDI input is a full-wave rectifier, the polarity doesn't matter. If the CDI input is a half-wave rectifier, apply the DC one way and see if it works and if not, try reversing the wires.

That's why I wanted a schematic. I'm a little hesitant to apply a DC voltage not knowing precisely what it's looking at. I had considered that there might be some kind of voltage multiplier that is charging the capacitor.

I think the regulation might occur at the input end. Checking with a scope showed a "big" sine wave at the stator plug when disconnected and a 20 v p-p square wave when connected to the CDI. Maybe this is a clue that if DC will work it better be less than 20v.

I may give that a try though. I can use a current limited 12 v. supply and the CDI that I bought cheap because somebody had shorted the wrong pins on the sidestand relay and dumped 12v into the g/y wire.
Do you have any info on the CDI other than what's in the Suzuki service manual?
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Old 10-25-2007, 10:24 PM   #4
strongbad
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The goop is hot glue. Some stators use it. Some don't. I've never found it necessary.

About the DC input to the CDI. I've thought about it a little more, and you're right. You need a schematic before you try it. If the CDI is deriving timing from the AC windings, then the input has to be AC, and the input has to come from the CDI winding specifically. No other winding will do.

I don't have any schematics or other info on Suzuki's CDI.
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Old 10-26-2007, 06:43 AM   #5
cwc OP
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Quote:
Originally Posted by strongbad
The goop is hot glue. Some stators use it. Some don't. I've never found it necessary.

I'm concerned about long term effects of vibration. I rewound probably 100 BMW alternator rotors before they became available at a reasonable price and virtually all of them originally failed due to vibration in a piece of wire about an inch long.

About the DC input to the CDI. I've thought about it a little more, and you're right. You need a schematic before you try it. If the CDI is deriving timing from the AC windings, then the input has to be AC, and the input has to come from the CDI winding specifically. No other winding will do.

I've thought a little more on that too. I think I will probe (eletronically) a bit and see if I can satisfy myself that I'm looking at diodes or more likely an SCR or similar. If so I think your idea of trying 12vdc might work.

I'm pretty sure the coil we are talking about is power only. The timing is from separate coils.
Thanks for the info and helping me think about this.
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Old 10-26-2007, 08:56 AM   #6
DRZmaui
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While you’re at it, check your Stator and rectifier wire coupler. There is a history of these things going bad. It appears the wires heat up, and melt the connection, this causes them to ground out, and cause all kinds of problems. It pretty well documented in thumper talk. I should know, it happened to me.

To correct it, most people just remove the coupler, and solder, and shrink wrap the connection.
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Old 10-28-2007, 07:53 AM   #7
cwc OP
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New CDI info

FWIW here are some CDI schematics

RG500 http://www.rg500.net/HTML/marc02/s_rg5cdi.gif
XT 600 http://www.transmic.net/gbindex.htm

www.transmic.net has info on building your own and some wierd and interesting links.
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