1980 GS550E only firing 2 cylinders

[bigP]

Hi guys, I've run into a bit of a head scratcher recently while trying to start my 550 up for the first time this season. Firstly I'll just add that the bike was in my indoor garage over the winter, left on a tender.

Ok, so here is the problem I'm having; When I press the starter, I'm only getting the full 12V to one of the coils while the engine turns over. On the other coil, I'm only getting about 1-3V while the engine turns over (also not getting a spark), then it spikes up to 12V right when I let off the starter.
I've been all through the wiring harness with a volt meter and I can't seem to diagnose where this problem is originating from. I've (possibly wrongly) ruled out a bad connection or corroded wire, as I don't see why that would be reducing current while turning over, only to let the full 12V through once I let off the starter. It seems like there is something drawing current from half of the starter circuit (one coil), but only when I'm on the starter switch.

Been all through the starter switch, headlamp wiring, turn signal circuit, and every connector from the coils back to the battery and I can't seem to find the source of what's sucking my power.

Any help is greatly appreciated! I'm itching to get out now that the weather getting nice.

- Peter

[tom203]

Which two cylinders are not firing? Understand that the ignitor makes and breaks the connection to the coils, so you get some funky meter readings as starter cranks over.

[bigP]

Cylinders 1 & 4 aren't firing. I'm only attributing the problem to the lack of voltage to these cylinders because the "2 & 3 cylinder" circuit is getting the full 12V while I'm on the starter. Which all 4 cylinders should be getting (to my knowledge).

[tom203]

Cylinders 1 & 4 aren't firing. I'm only attributing the problem to the lack of voltage to these cylinders because the "2 & 3 cylinder" circuit is getting the full 12V while I'm on the starter. Which all 4 cylinders should be getting (to my knowledge).

Ok. Reverse the connections from ignitor to the ignition coils to see if you now get spark on 1 and 4 ...obviously it won't start, but if you got spark, it probably means one half of your ignitor is dead.
The 550 ignitors seem failure prone, fortunately a dyna S system can save you.

[Redman]

Cylinders 1 & 4 aren't firing. I'm only attributing the problem to the lack of voltage to these cylinders because the "2 & 3 cylinder" circuit is getting the full 12V while I'm on the starter. ..............

Good. You answered one of my question before I asked it.

My other question, when you say measured ## volts at the coil, do you mean voltage to ground or do you mean voltage across the coil (both meter leads on the coils two connection)? I suspect the latter.

The supply of the +12v to each coil is right in parrellel with only a short length of wire in between.

The fact that you notice the symptoms only on one coils and not the other and only while cranking is great troubleshooting.
Assumming you are measuring these voltages across the coil, I too suspect this symptom you noticed this is related to what the ignitor is doing.

If you do prefrorm the test suggested above (swapping connectors or swapping coils), I suggest you do this with all the plugs removed from the cylinders.

.

[bigP]

Thanks for the suggestions guys!
I'm definitely going to try what tom203 suggested and reverse the connections from the ignitor. I am at my parents house for the rest of the week, so likely won't get a chance to do this until Friday night/ Saturday. Regardless, I'll post my results, whether successful or otherwise.

[baesorenson]

My GS1100GL 1 and 4 are not firing. Would this be the same procedure?

[bigP]

Update:
I was not able to get it started unfortunately, but rather I'm more confused now than before...
Cylinders 1&4 are getting the full 12V when the ignition is "on" and when I turn it over, whereas cylinders 2&3 are only getting ~5V when the ignition is "on", and still doing the voltage spike when I let off the starter button. BUT, for some reason cylinders 2&3 are getting spark and 1&4 are usually not (sometimes yes, usually not).

At this point, I'm left thinking it must be a combination of the ignitor and the coils. I plan to drop the bike off at a shop sometime next weekend to see if they can figure it out, before I drop ~400USD into A dyna ignitor and coil setup.

Thanks for the help everyone! I'm afraid this electrical stuff is beyond me.

[tom203]

". BUT, for some reason cylinders 2&3 are getting spark and 1&4 are usually not (sometimes yes, usually not)."

Probably the ignitor (cuz it's a 550), but could be poor connections. A Dyna S igntion setup is about $130. you don't need their ignition coils.I'd quess that any dealer will charge you that amount just for a look. These old critters need personal care to keep them happy.

For the dyna s, you need to know what kind of ignition that your 550 came with..KD or ND- here's the ND unit

https://www.ebay.com/itm/Dynatek-Dyna-S-CDI-Ignition-Suzuki-GS550-GS750-GS850-GS-750-1977-1983-DS3-2-ND/381976040945?epid=171085401&hash=item58ef8bd5f1:g:c2YAAOSw4UtWTlvY&vxp=mtr

[bigP]

I'll pull the ignitor later today and see if I can identify whether its ND or KD.

Side note: is there any chance it could be my CDI box giving me this problem?

[tom203]

I'll pull the ignitor later today and see if I can identify whether its ND or KD.

Side note: is there any chance it could be my CDI box giving me this problem?

Good news there is no CDI ....the ignitor is cigarette pack size box - this takes a signal from the signal coils which are mounted on a metal plate on right side of crankshaft. The ignitor then interupts the current flowing to the ignition coils.
on the signal coil plate ,look for a small logo like "ND" stamped on it. I'd suspect that you hsve the ND setup.