See full version: Why do my ignition coil keep going bad after I replace it
At some point, with excessively high voltages, the insulation resistance rating of the rubbers/plastic etc all used to make the ig. components is exceeded, things start to ionize and arc'ing (Tesla coil style) starts happening all over the place. Super high voltages have magically ways of getting out/through stuff
Basically, the CDI Ig. uses the induced voltage (magneto if you will) generated from the flywheel's perm magnets passing by the specific exciter coil's in the stator to charge a capacitor (some use an internal oscillator tanking at some resonate LC freq, whining away). that lives in the CDI box (Switch Box)..The "C" (capacitor) in the CDI box is in series the the primary side winding of the ig. coil. here
Say something like 1:100, so if the cap normally charges to say 200VDC on it the secondary of the ig.s coil would have 20,000VDC [links]
To fire the plug, the charged up cap is discharged (SCR (or FET) grounds the cap via signal from the "other" flywheel stator trigger winding) through the ig. primary coil winding and through the magic of Faraday's Law, the "turns ratio" creates a proportional stepped up voltage on the secondary winding of the ig. coil of say 20KV that arc's at the electrode of the plug. [links]
Was the coil replaced with new, and did it come with a new plug wire?
Have you replaced the spark plug?
Is there a even air gap between stator and flywheel magnets? more
Obviously the only reason any coil opens up is it burns open. And that means too much current flowing through the coil. Is there any ballast resistors missing or anything like that in the top ignition setup? I would swap everything from the top circuit to one of the other cylinders and see how that works out. And I would even change the spark plug as well. If that doesn't fix the top cylinder problem, you need to check what is feed that top coil. That would be the next item to test and/or replace. JMHO
There is no 12 volt *ANYTHING* in your ignition system. The spark come from the CDI. The CDI is powered off a high voltage AC winding on your stator. The CDI is triggered by another lower voltage AC winding on the stator. Then somebody tells you you should have 12 volts at the coil, and then you measure 12 volts. This has me a little worried. here
The following was measured with an oscilloscope at engine idle. At cranking speeds the waveforms would be the same except the amplitude would be smaller, and the time between pulses would be longer. An oscilloscope is just a fancy voltmeter that is able to measure very fast moving voltages and plot them graphically over time. The horizontal axis is time, the vertical axis is voltage: Use the horizontal scroll bar to see the detail on the right of the graph.
Sir it doesn't matter about what you are measuring from the output of the CDI to the coil, with a standard mulit-meter it is inaccurate period. The speed at which the voltage discharges is so fast a standard volt meter will not read it fast enough thus the steady drop in your readings. The CDI fires at and incredibly fast pace, it fires twice per revolution of the flywheel, just imagine how many times that is at just a 2000 rpm idle of the engine.
I also belong to that forum you linked to and if you read the post you'll see he said what you've been told here: here
Below is what the voltage should be on your igntion coil. There are actually two different waveforms because I have two different brand CDI's. Both work fine. CDI's should be considered black boxes that take in the stator high voltage AC, the trigger pulse. the kill switch connection, and then produce an energy pulse that will couple through the ignition coil to fire the plug. There are many, many ways to do this. I think these two examples show how bizzare the differences in designs can be. So what what would your meter show for these waveforms? I have no idea. It depends on how the meter is designed inside. Different meters will read differently. [links]
Attach the black (negative) lead of the multimeter to the outer, negative terminal of the ignition coil. here
Connect the red (positive) lead of the multimeter to the outer, positive terminal of the ignition coil. Turn the reading dial on the multimeter to ohms to measure resistance of the primary pickup coil. (The Greek letter omega denotes ohms.) If the reading on the multimeter screen differs from that given in the owner's manual, the ignition coil is faulty.
Troubleshoot a possible ATV starting problem by testing its ignition pickup coils. Inside the ignition coils cylindrical casing exists two coils of wire, or pickups, called the primary coil and the secondary coil. The primary coil receives voltage from the ATV battery. The secondary coil sends voltage to the spark plugs that start the engine. Each coil has a specific operating resistance specified by the manufacturer. This resistance prevents too much electrical current from passing through the wire, so the correct voltage may be reached by the ignition pickup coils.
Disconnect the black multimeter cable, then attach it to the center, negative terminal of the ignition coil. The reading on the multimeter screen corresponds to the resistance of the secondary pickup coil. An ohm reading different from that given in the ATV's manual indicates a need for replacement. here
[links]
At this point I think something may be wrong with the stator but it puts out a constant 33 volts AC when cranking so it doesn't look like anything's wrong with it. more
They are AC (6-wire) CDI boxes and I've tried 4 of them now. I've been through 3 coils. I'm using a single stage hotter plug to help it fire. more
I can't get a good enough spark to start the engine unless I am getting 12 volts out of that CDI box to the coil, and that only happens for the first few seconds of the life of the CDI and then sometimes if I have the bike sit for a few days and come back, I've noticed I can get a CDI to start back at 12 volts and do the same decline in output voltage. here
The only way I've been able to start the bike is by cranking it with 400 amps real fast a few times until it starts. Once it starts it's good - there is no misfiring or anything and I can ride it as long as I want but as soon as I turn it off I can't get a good enough spark to start it. [links]