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Coil primary wiring 25 Jul 2015 18:25 #682729

  • SWest
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Did you try cutting off 1/4" and retighten them?
Steve

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Coil primary wiring 25 Jul 2015 19:29 #682736

  • DGA
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I took cylinder #1 which has no spark and wound it and it unscrewed out of the coil, and was like you were saying, has a screw in there which winds into the center of the wire.. Wondering about the plug caps now, they are NGK, are those OEM or? Other questions, do these bikes have generally weak ignition? I see some mod ignitions some talk about, does that make a big difference?

My brother had an '81 1100 years ago, was an EFI bike and the system was dead so he swapped it for carbs. It ran ok we thought, and we rode it around awhile, knowing it wasn't running right, but were generally pleased with it. One day he decided to put new plugs in it. Started it and it suddenly ran smooth. Oh crap that thing was fast then, we had been riding it on two cylinders the whole time! I used to like to try to touch the throttle stop in the first three or four gears on it and then watch the street lamp poles buzz past like they were a picket fence.
"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750

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Last edit: by DGA.

Coil primary wiring 25 Jul 2015 19:34 #682738

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Did you notice any green or odd colors at the tips of the wires? Pics of your plugs?
Steve

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Coil primary wiring 25 Jul 2015 22:44 #682765

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No the wire ends looked ok really, copper core wires too. Plugs were brand new, some are a little sooty, none fuel fouled though. I checked the wire and plug boot for resistance and there is some, 500 ohms I recall, Didn't think there should be any with copper core wires.
"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750

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Coil primary wiring 26 Jul 2015 10:10 #682809

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Well this is strange. I have spark to three cylinders. I swapped plug wires around, etc and trimmed to new ends, comes down to one coil has a dead output. Just one. How is that possible? These are aftermarket coils, probably Chinese. Anyone ever see this before?
"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750

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Coil primary wiring 26 Jul 2015 10:44 #682818

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DGA wrote: Well this is strange. I have spark to three cylinders. I swapped plug wires around, etc and trimmed to new ends, comes down to one coil has a dead output. Just one. How is that possible? These are aftermarket coils, probably Chinese. Anyone ever see this before?

I have not seen that before either.
That might mean that inside the coil casting, there is no connection to that one HT lead.... and I am not so sure the other end would fire the third plug on that coil if the other end was grounded.... ???
The HT secondary coil has two ends.... each connected to plug wire.
If one plug wire fires, the other end should fire 180 degrees out of phase.
Bruce
1977 KZ1000A1
2016 Triumph T120 Bonneville
Far North East Metro Denver Colorado

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Coil primary wiring 26 Jul 2015 14:25 #682839

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Well that's better. I forgot I had an '80 KZ750 sitting here in the shop in pieces, so I used a coil off that. Bike goes pretty good now on all four cylinders. Was still lean at low end so I went from 3 to 3.5 turns out on the pilot screws, but it does have 37.5 pilots in it, I will order 40s for it.
"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750

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Coil primary wiring 26 Jul 2015 18:45 #682886

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It's possible for high tension voltage to flow though the secondary loop with the firing of only one of the spark plugs.
Here are two examples:







Old hard cracked worn-out spark plug wires may leak voltage through the insulation and short to or partially short to the engine head.
Fooling with the less than perfect plug wires may randomly leave them in a position where there's more or less leakage depending on their proximity to the engine head, which can produce mixed and widely fluctuating results during testing and riding.

The high tension leakage can get so bad that the rider can feel a buzz when touching metal parts on the bike, such as for example upon switching the petcock to reserve.

Spark plug covers/caps/boots often have a built-in resistor.

Dyna solid core plug wires come with non-resistor caps already built in.

Good Fortune! :)
1973 Z1
KZ900 LTD
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Last edit: by Patton.

Coil primary wiring 27 Jul 2015 18:40 #683059

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I placed the plug directly in the coil itself to check, no spark then either. Something wrong inside the coil itself I think.
Since that I found the other coil has weak spark on one side so I swapped it too, so have two stock coils now. It runs on all four, but does not stretch my arms out like I think it should. Plugs look a little lean, especially since it has three main jet sizes larger at 125. I shut it off and spray water on the headers and cylinder 3 does not steam off as much as the other three cylinders. I need to check compression, any other ideas?
"83 KZ1100 Spectre, '81 Yamaha XV750 Cafe, '74 Kawasaki H2B 750

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