Diagnosing no spark condition on 82 GS450.

[Guest]

Hey guys, I'm finally getting a multimeter after the ignition on my 82 GS450TX. Previous owner indicated the CDI box was bad, and obviously I'm not getting spark. After poking around a little I noted that when the ignition is on, not only am I getting 12v on the white/orange lead on each of the coils, I am also seeing 12v on both the wires (can't swear to the color right now) coming from the ignition box. So I have 12v at both of the coil connections. And they both go on and off with the ignition switch, and do not change when cranking the engine over.

So on each coil, I was expecting to see 12v on the one connector that runs off the kill switch, and nothing on the other wire (from the ignition box) until you crank it over, at which point you should see some kind of pulse to trigger the coil. At least I think so lol. The capacitor should discharge, sending some short, high-voltage pulse that the coil takes and fires the plug with, no?

So anyway, does that mean my ignition module is toast, or what is the next thing to check here?

TL;DR: Getting 12v on the 2 lines from the ignition box to each coil, and no change when engine turns over.

[Steve]

First thing to check is your terminology.

There is no "CDI" on the bike. Never has been. Anyone who calls it a "CDI" is just plain WRONG.

That magic little box is called the "IGNITOR", which is unfortunate, because it doesn't really "ignite" anything.

If you are familiar with the old-school concept of points, condensors, coils and distributors, you will understand the basic concept of your bike's ignition system. The most obvious difference is the lack of a distributor, there are two coils, instead.

The way that system works is that the points are closed, allowing current to flow through the coil to ground. Inside the coil are windings around a metal core, which set up a magnetic field. When the points open, that magnetic field collapses and that collapsing field sends a rush of current (at a much higher voltage) through a second set of windings to the spark plugs. Got that? Current flows, magnetic field is generated. Points open, field collapses, spark is generated.

Now, take out the points, put in a box full of transistors. Call that box an "ignitor". You now have your bike's ignition system.

There is NO capacitor to discharge, nothing is "triggered to fire".

You are seeing 12 volts on both sides of the coil because they are not connected to ground. It is the ignitor's job to connect them to ground to complete the circuit so current can flow to create that magnetic field.

By the way, what is the "TL;DR:" thing at the end of your post? Looks like some sort of summary, but the letters don't mean anything to me. You need to adjust your thinking in that line, though. Think of the wires going from the coils to the ignitor, not the other way around.

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[gs45082]

First thing to check is your terminology.

There is no "CDI" on the bike. Never has been. Anyone who calls it a "CDI" is just plain WRONG.

That magic little box is called the "IGNITOR", which is unfortunate, because it doesn't really "ignite" anything.

If you are familiar with the old-school concept of points, condensors, coils and distributors, you will understand the basic concept of your bike's ignition system. The most obvious difference is the lack of a distributor, there are two coils, instead.

The way that system works is that the points are closed, allowing current to flow through the coil to ground. Inside the coil are windings around a metal core, which set up a magnetic field. When the points open, that magnetic field collapses and that collapsing field sends a rush of current (at a much higher voltage) through a second set of windings to the spark plugs. Got that? Current flows, magnetic field is generated. Points open, field collapses, spark is generated.

Now, take out the points, put in a box full of transistors. Call that box an "ignitor". You now have your bike's ignition system.

There is NO capacitor to discharge, nothing is "triggered to fire".

You are seeing 12 volts on both sides of the coil because they are not connected to ground. It is the ignitor's job to connect them to ground to complete the circuit so current can flow to create that magnetic field.

By the way, what is the "TL;DR:" thing at the end of your post? Looks like some sort of summary, but the letters don't mean anything to me. You need to adjust your thinking in that line, though. Think of the wires going from the coils to the ignitor, not the other way around.

.

Thanks Steve!

Sorry I'm pretty ignorant on how all this works so bear with me here. I was kinda careful not to call it CDI. I really just meant to point out that's what the PO told me, and to take it with a grain of salt. So you're saying that the igniter box (or whatever we want to call the magic black box) connects that leg of the coil to ground and that causes the spark? Because I think we can establish that isn't happening, so there's either a problem either in the box itself, or there's something the box needs that it isn't getting (like a signal from the timing pickup, or??). Can I ground that wire with a jumper and expect to see a single spark from the plug?


"TL;DR" stands for "too long, didn't read" so yeah it's just a summary. I try to do something like that when I've filled a post up with a lot of details so as not to lose the main point of the post.

[Steve]

"TL;DR" stands for "too long, didn't read" so yeah it's just a summary. I try to do something like that when I've filled a post up with a lot of details so as not to lose the main point of the post.

I find it rather ironic that you basically apologize at the end of a 'long' post with an abbreviation that means it was a long post.

Maybe it would be better to start with "WARNING: long post follows, here is the summary: ..."

Do you have a manual for your bike? If not, do a quick search here on GSR or even just Google "BikeCliff", you will find his site. That is our "library" where all the manuals and tutorials are stored.

When testing, BE CAREFUL with the ignitor (yes, that is the official Suzuki term). DO NOT just ground it out. You can remove the connector that joins the coils to the ignitor and ground each of the coil wires for testing, but do NOT ground the ignitor wires. When you ground the coil wires, you might get a little bit of a spark from the wire when you connect it, but the spark at the spark plug will happen when you LIFT the wire off the ground. In the manual, there is a test for the triggers on the crankshaft, and there is also a test for the ignitor, but follow that one TO THE LETTER, as it tells you to connect a flashlight battery to the inputs, but it is VERY important that you get the polarity correct or you WILL fry the ignitor.

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[Gorminrider]

Excellent description there ^. One thing that comes to mind is that cheapo digital multimeters are really poor at reflecting fast changes so if you are cranking with a battery, it may be that you will not notice the interruption on it.
Also, PO's (previous owners) can steer you down their own dead end. Take nothing for granted.

[Nessism]

Those 450 ignitors weren't very robust. I think when your R/R goes bad and the charging system voltage spikes it takes out the ignitor. Not sure what to suggest other than looking for a good used unit or moving to a Dyna ignition. There is a tutorial on how to make your own 450 ignitor too. Not for the faint of heart though.

[hank3fan]

Those 450 ignitors weren't very robust. I think when your R/R goes bad and the charging system voltage spikes it takes out the ignitor. Not sure what to suggest other than looking for a good used unit or moving to a Dyna ignition. There is a tutorial on how to make your own 450 ignitor too. Not for the faint of heart though.

I can't find the link. Do you mind providing?

[Big Rich]

IIRC, it is possible to replace the GS450 Ignitor with one from a GS500. The spark curve is different, along with the wiring harness, but it would beat trying to make a new ignitor.

[Thumper88]

I was lucky enough to have a parts bike to replace mine, but check these links out:

http://www.thegsresources.com/_forum/showthread.php?171781-82-450-Igniter-Repair-Replace-or-Make&highlight=dyna

http://www.thegsresources.com/_forum/showthread.php?182719-81-GS550T-ignition-replica-for-a-few-euro-!&highlight=diy+ignitor