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Discussion Starter #1
Hello, I’m new to the forum but I’ve been reading a lot of posts that I found on Google to try to resolve my problem. The people on this forum were very impressive.

No spark started as intermittent problem but now it’s no spark. I’ve followed the manual and a lot of the testing procedures that I’ve seen in this forum for checking voltages, ohms and continuity to no end. Everything checks out. I bought a cheap cdi, it was AC. Bought another one from Amazon and it doesn’t say Ac or DC. I’m going to try baking mine next. I’ve checked the neutral and reverse circuit and grounded them. Nothing.
The only time I see a spark in my tester is if I hold the start button and slowly put it in gear, I get about 3 good sparks. Back to neutral, no spark. Hold button and put it in reverse I get 2-3 sparks. Back to neutral I get 1 spark. The only other odd thing is the neutral light never goes out. It slightly dims when in gear. I hate throwing parts at something when every test shows the OE parts are good. Any help would be greatly appreciated.
 

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Sorry, I missed this post the day you posted it - I need to know which of the 3 models of 300 you have - the plain 300 2x4, the 300EX 2x4 or the 4x4 300FW - they were all DC CDI, but the EX is wired differently than the 300 and 300FW and uses a different CDI box. Put an AC unit in a DC circuit and it will let the smoke out in a short time.
 

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Discussion Starter #4
It’s a plain 300 2wd. I’m gonna bake the old cdi tonight. Could I have let the smoke out of something else now?
 

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To start troubleshooting a no spark issue, first verify you have 12v on the black/white on the two pin plug at the CDI box

There are no tests for the CDI unit, so you have to eliminate everything else first and then blame the CDI unit - they actually seldom fail. More usually it's wiring connections or the stator.
 

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Discussion Starter #6
I have 12v on the Black/white wire at the CDI. I am pretty sure that I have tested continuity through every wire in the ignition system
 

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OK - continuity is fine, but it's output that is important. To accurately test the ignition system, you need a peak voltage tester or oscilloscope. With one of those diagnostic tools, you just have to hope the gambling gods smile upon you.

With a peak voltage tester or o-scope, you can check the output of the pulse coil, the CDI unit and the primary coil.

Where the idea of baking a CDI unit came from is about as useful as freezing a hard drive out of a computer. IT DOES NOTHING OTHER THAN MAKE IT HOT OR COLD! Most CDI unite fail with heat, so what's baking it going to do for it. I recommend you put it in a bowl of water and microwave it.

It's this simple, the CDI unit gets 12v from the battery to charge the Capacitor in the Capacitive Discharge Ignition unit - the pulse (trigger) coil generates a voltage (typically 3 to 5 volts peak - a single pulse goes to the CDI unit) - the pulse voltage triggers the unit to discharge the capacitor through the primary coil - typically an approx. 100v pulse from the capacitor discharges to ground through the coil - this 100v pulse causes the coil (an auto transformer) to generate about a 30 to 40,000 volt pulse to the spark plug causing a spark to jump the gap - with a peak voltage tester or o-scope all these spikes can be measured - without the diagnostic equipment, you have to gamble as to which part is not functioning.

Now the way it work out, the most common problem is connections, especially ground connections. Of the individual components, CDI fails the most often in this system because it is subject to rising and falling DC voltage from the battery as it charges and discharges - the pulse generator almost never fails and the primary coil is simply a pair of windings that don't move, is encased in potting material, almost never gets moisture into it and is not particularly affected by changes in temperature or vibration. The spark plug cap has a resistor in it that can fail and the spark plug it what causes most loss of spark problems.

The best test of the CDI unit is to put on a running machine - if it works on the running machine, then it is good - the second test is to put the running machine's CDI on the non running - if the non running becomes a running vehicle, then obviously the CDI was the culprit.

Good luck
 

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Discussion Starter #8
Had a late day today, I’ll try to run down a meter tomorrow. Does the fact that I only get a spark now when the gearshift is moved from neutral to first or neutral to reverse clue you in to something? Thanks
 

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Discussion Starter #9
I’ll have a DVA Adapter here tomorrow to get those tests done. Can you break down what I’m testing and the readings I’m looking for? The gearshift movement and getting spark is weird to me also.
 

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It's possible to have a poor connection or faulty stator preventing spark - in this case, a faulty rec/reg (shorted diode) on the leg feeding the CDI could cause the problem. Try unplugging the rec/reg and see if that restores spark - if it does test the stator and the rec/reg. Stator output is supposed to be checked with the engine running, but in this case the CDI is only looking for a signal, not a specific voltage , so any voltage reading on the yel/wht wire is sufficient
4392

yel/wht wire is 4th wire on the 4 pin connector as depicted in the graphic - 1 to 35 volts is adequate - if 0v, unplug the rec/reg and recheck while cranking the engine
4393
 

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Discussion Starter #11
I’ve got 6.4v on the y/wh wire at the cdi with the cdi unhooked. I checked the bk/ yl stripe wire at the coil and I get nothing.
 

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When I was testing the coil input I accidentally turned my meter from DC to AC settings and before I turned it back quickly I could see that the meter was getting a reading. Does that verify that I’ve bought another AC cdi?
 

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No - only the seller can tell you if it's an AC or DC CDI, but plug an AC CDI into a DC circuit and it will let the magic smoke out in a short time - when the smoke gets out, you know it will not work after that.

You can't test a coil on DC unless you have a peak voltage adapter on the meter
 

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Discussion Starter #17
The company I bought the adapter from calls it a DVA ( Direct voltage adapter) to find Peak Voltage. Anyway, back to what matters, you may be right that I need another CDI. But I can still get a spark and can read voltage with the adapter on my DMM set to DC when I move the gearshift into first or reverse gear while holding the start button.
 

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Try grounding the wire from the CDI unit that goes to the neutral switch as close the the CDI unit as possible to rule out the neutral switch as a possible cause of the problem - does this pic match the wiring on your ATV?
4407
 

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Grounded the neutral switch wire with no luck. Still no spark.
Well, that just eliminated the neutral switch as a potential problem - that only leaves power on the blk/wht wire, ground on the green wire, the voltage from the pulse generator, the CDI unit, the coil and the wiring.
 
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