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650 coil voltage question

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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I just purchased a 1982 GS650GD and have some questions. Problem...Will not start or even try to fire. Compression is good, 135 per cylinder. Removed carbs and they look very clean so I cleaned the jets and reset the float levels per Clymer specs. The spark seems week on each plug, kinda thin white/blue arc. With 12.5 volts at the Batt I have only 10.0 at the coils. I removed each neg wire from the coils and when I remove the white wire from one coil the voltage jumps back up to 11.8 volts so I tried this wire on the other coil and it also dropped to 10 volts. I then put the wires back on the coils and removed the igniter plug at the fuse terminal location and my coil voltage is 11.8 on both coils. This tells me there is a path to ground through the igniter from the white wire output but when I measure white wire to ground it has no Resistance. Could it be that transistor is firing to ground when I turn on the key? If so how is it possible for this side to fire the plugs at all?

Anyway it seems to me I have a bad igniter. If you guys disagree, please tell me why and what to check for next.

Do any of you guys know of a good salvage yard that may have one? I would go to points if I knew where to buy what I need to do it.

Thanks
JB
 
I suspect the coils itself, had a similar problem with my bike, turned out the coils were going bad... did you measure the primary and secondary resistance of the coils? Ignitor is OK or broken I've been told, not something in between.
 
I'm currently working on the similiar problem with my 1980 GS1000G. I does seem to be weak spark and I also find my O/W wire to the coils have lower voltage than the battery. I was about to concentrate on the ignitor but I've been dicussing my wows at work and found that a coworker had a problem years ago with a dirt bike and we put our heads together. We think it's related to resistance in the battery feed to the coils and It makes sense in my case. The coil battery power is feed to 2 parallel legs via a wire with many connections ( fuses, wires, connectors switches) . One path goes through a large connector twice and via the kill switch then off to the coils via 2 smaller connectors. The other parallel leg goes to the ignitor. When unplugging the ignitor my voltage goes back to 12.4. Looking at this electronically, the voltage across any leg of the parallel circuit will remain the same no matter what the resistance in each leg. The ignitor will have some internal resistance so if you look at the total circuit I believe it might have resistance in the connectors, fuses, switch etc which will act as a series resistance and cause voltage drop to the coils when theinternal resistance of the ignitor is connected.

Before you go out and spend money I would plan on getting a wiring diagram and tracing your battery power from the battery to the coils. Place your negitive meter lead on the battery negitive and touch variuos points along the path to the coils (both sides of connectors and switches) and look for the voltage to drop. If the voltage drops to the battery as soon as the IGN switch is turned on, suspect the battery. If the voltage falls from one side of the connector to the other, suspect that connection.

I plan on spending another 4 to 5 hours tonight to solve my problem and WHEN I find it, I'll let you know.

Good Riding!!!!!!!!!!!!
 
Thanks for the reply guys. I don't know why I didn't get a notification email that this thread had a reply as I think I have that option turned on !

I just replaced the igniter today and have the same problem. There is a hundred bucks shot in the butt! I have purchased coils from e-bay and am waiting for them to arrive. It would help to know just how much voltage drop to expect at the coil + terminals when the ignition is turned on from a good running bike.

I have another question that I can't seem to find the answer to in the Clymer manual. It says the firing order is 1,2,4,3 but does not tell you which cylinder is what number! The guy at Suzuki told me the cylinder numbered 1,2,3,4 from left to right while sitting on the bike and the coil on the left side of the frame fired 1,2 and the coil on the right fired 4,3. If this is correct my plug wires are in the wrong place. I know this doesn't have anything to do with the low voltage problem but it is something I will have to address after I find the LV problem.
 
JB said:
Thanks for the reply guys. I don't know why I didn't get a notification email that this thread had a reply as I think I have that option turned on !

I just replaced the igniter today and have the same problem. There is a hundred bucks shot in the butt! I have purchased coils from e-bay and am waiting for them to arrive. It would help to know just how much voltage drop to expect at the coil + terminals when the ignition is turned on from a good running bike.

I have another question that I can't seem to find the answer to in the Clymer manual. It says the firing order is 1,2,4,3 but does not tell you which cylinder is what number! The guy at Suzuki told me the cylinder numbered 1,2,3,4 from left to right while sitting on the bike and the coil on the left side of the frame fired 1,2 and the coil on the right fired 4,3. If this is correct my plug wires are in the wrong place. I know this doesn't have anything to do with the low voltage problem but it is something I will have to address after I find the LV problem.
Click to expand...

On a good bike the voltage drop is maybe a few tenths at most.

Cylinders are 1 to 4 when sitting on the bike

Left coil fires 1&4
right coil fires 2&3

And read my previous post please.
 
rockinGS I did read your previous post and I agree with you 100%! I guess what I really need to know is what the current draw is on a good bike at the + side of the coils. As you know when resistance increases current decreases and I am showing about 1800 - 2000 MA or 1.8 - 2 amps at 10.5 volts. Maybe I can figure this out if the manual tells me what the coil resistance is. But that would only apply when the neg side of the coil was at ground potential and this only happens when the igniter fires and takes the neg side of the coil to ground through a transistor or some kind of solid state device! My head is starting to hurt!:D
 
I know what you mean about your head hurting :? . I troubleshoot electronics every day at work and this bike is much harder to solve :x . I still have my coil voltage 2 volts lower than battery voltage with the ignition and kill switch ON. I didn't think this would be such a job, so I haven't taken notes to keep my thoughts in order, thus I keep going around and around in my mind :? . I have when measuring ohms from the battery positive connection to the O/W wire connection on the coils 0.5 ohms, which seems too small to worry about but my latest plan is to remove all molex connectors and solder and heat srink to eliminate resistance. I'm even wondering about the wire itself???? I do notice that I seems to get a good spark when I first start cranking and when I stop cranking. This seems related to the current draw of the starter which gives less to the coils. I seem to have many small sparks at the plug while I crank. I wish we could find a member that had this happen to them and see what it took to solve their problem :wink: . Please keep me posted about your progress :D .
 
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