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Discussion Starter #1 (Edited)
I have an 89 VN750 I bought last yr. After it I figured out it was only running on the front cylinder, I pulled the carbs and cleaned them. I also did the ear shave after some profanity towards the air box. Now it's back together and I have narrowed the non firing cylinder as electrical. I get no timing light on either rear cylinder lead or spark. I swapped around coils with no change. I checked igniter box values with a VOM, a few didn't spec. Of course I don't have Kawi tool. Today, I reversed pickups to check if the rear would trigger the front via alligator clips. It does, but I can't get the front to fire the rear plugs. I checked for continuity at all primary coil wires and igniter box as well as pickup plug to igniter box.At this point, I have come to the conclusion that the igniter box is faulty. Any thoughts? I also jumped the - primary wire right to the box. Voltage at both coils was identical at 11.8 not running, ign switch on.
 

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11.8 seems a little low....is you battery weak?
12V and above would be better.

If the battery voltage is low, then the ignition my not work well.
If the voltage at the coils are lower than the battery voltage, you have a worn wiring harness.

check out the coil mod HERE
 

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Discussion Starter #3 (Edited)
My battery was low from starting it, so I charged it up some showing better numbers. I also tried something else. I used the primary wires for the front coil to run the back just to see if it worked via jumpers. No spark. Ran a sep ground to the rear coil along with a + wire right to the + side from the battery along with the black wire from the front coil, no fire. This was a working coil that was on the front. I also swapped spark plug wires and checked resistance. Running the primaries from the rear coil to the front coil produced spark. It sounds like a bad coil now, but I swapped them to eliminate that....A ghost......
 

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I hope you didn't somehow damage the good coil...not sure how you could have to be honest.

It is very rare that a ignition control module goes bad, but I suppose it could be the case.

You need to test each coil and get at least one good coil installed in each position to see what is really going on.....my advice is to go back to the beginning and check the obvious and do one thing at a time to make sure you are not missing something simple.
 

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..have a vulcan good day!
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Coils receive a pulsed ground from the ICM (Ignitor box)...
Full time battery ground to coil will not allow coil to pulse.
WilliamTech
 

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Discussion Starter #6
I grounded to the coil base, sorry. Not the pulse side. I swapped plugs as well just to be sure I didn't get a shorted one that allowed direct ground of the spark. I did get a slightly out of range measurement of secondary resistance at 31.6 kohm on the back coil. Primary right on the money. To me, this points right at the rear coil.
 

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Discussion Starter #7
Found the source of the problem. The harness connector that connects the pickups to the ignitor box under the seat had a poor connection. Cleaned it a little and manipulated the tabs slightly to get a tighter fit, all is well there now. Now to get it back together and adjust/sync carbs. Thanks for the advice.
 
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