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My 1979 GS 1000 has a Dyna S and Accel coils and 8.8 mm suppression wires installed by the PO. I lost spark on 1 and 4. That coil primary reads open. I do not get a reading from the iron core where the mounting holes are drilled to either output as I would think I would, but see 14K ohms from one output to the other. I have a set of Dyna Green dual-output 3 ohm coils, read about 4.5 ohms across the primary, and nothing across the core to output, one coil reads 14K between the outputs, the other does not. I'm figuring that the Accel coil (the 1 and 4 coil) with the open primary is bad. The Dyna Green that shows 14K ohm between ouputs seems good, but what does anyone think about the one that seems open between the two outputs? Bad? I was going to replace both Accels with the Dyna Greens, but now I don't know. Any opinions? BTW, today is a beautiful fall day; I REALLY wish I was riding instead of troubleshooting!
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1979 GS 1000 -
Having some trouble following exactly what measurements are where based on your description, but an open across either the secondary or the primary means the coil is bad, or that there's a break in the wires somewhere.
The spark plug caps are the secondary side of the coil, so you should see an open between that bracket and either plug cap. (In a good coil, at least.) I'm not sure how your coils are wired on the primary side. Based on the schematics in my manual, the stock coils have two low-voltage wires for the primary and two high-voltage wires for the secondary. The mounting bracket is not part of the system, electrically speaking. Dunno about Accels and Dynas, however.
Since coils rarely go bad, see about disassembling or removing the spark plug caps and repeat the measurements, if you haven't already. -
I shouldn't be the plug caps, as BOTH 1 and 4 have no spark; two completely different wires/caps. The coil with the open primary is the only common factor that seems bad. It's possible the Dyna S pickup for 1 and 4 is failing, but the coil DOES seem like it has an open primary, so it seems like that is the first obvious problem. I'm more concerned if one of the Dyna coils, the one showing no reading between the two outputs, is possibly bad, since my plan had been to change out both. I bought these Dyna coils used a while back from a member here on the GSR, but never had a reason to check them out before.1979 GS 1000Comment
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I'd be inclined to think it is the coil gone bad. You could try swapped the 1-4 with 2-3 and redo the checks. If the problem persists on the 1-4 circuit it's not the coil, if the problem transfers to the 1-3 circuit it is the coil.Originally posted by jknappsax View Post
JAGComment
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The secondary needs a return path from the base of the spark plug back to the coil, this is usually through the mounting tabs. Although the negative terminal could provide the return this would be unusual.1981 GS650G , all the bike you need
1980 GS1000G Power corrupts, and absolute power corrupts absolutelyComment
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The plug caps are what make up the entire secondary side of the coil, so if either wire or cap has a big enough break, neither 1 or 4 will have spark. When the magnetic field inside the coil collapses, a high-voltage current flows from one plug cap, through the spark plug, through the engine head, through the other spark plug, and then back up the other plug cap into the coil.I shouldn't be the plug caps, as BOTH 1 and 4 have no spark; two completely different wires/caps
That's probably where the fault lies, then. Although I'd second JAG's suggestion of swapping the coils if you haven't already.The coil with the open primary is the only common factor that seems bad.Comment
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The wires are Accel suppression wires, without resistor caps, not the original NGK caps, and they read ok with an ohmmeter.1979 GS 1000Comment
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