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Discussion Starter #1
I have a 300 ex that has no spark, is a full jb mod has reverse inhibitor bypass as well as neutral bypass and cut harness. I have no spark, have checked all connections and plugs. Can put test light in yellow/white wire from stator and get consistent light flashes at cdi plug, have 12v at gray black wires also. I’m thinking it’s cdi but want to make sure before I have to buy another as it’s a performance cdi and it’s not my atv
 

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I do not know what a jb mod is so that's meaningless - at any rate do you have 12v between the black/white wire and grn/wht wires at the CDI unit? If yes, use the chart to check resistances.
4357
 

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Discussion Starter #3
I do not know what a jb mod is so that's meaningless - at any rate do you have 12v between the black/white wire and grn/wht wires at the CDI unit? If yes, use the chart to check resistances.
View attachment 4357
Jb mod is a built atv mx quad so bare minimum wires and parts everything that was unnecessary was cut out. All resistances check out new stator, pulse generator, coil, spark plug boot, spark plug
 

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Discussion Starter #5
Well, all that is left is connections, CDI box and battery.
I came to the same conclusion the old cdi was humming and guy had another cdi but it was a cheap China one compared to the performance one that was 150$ And I just don’t think it’s sending the signal to coil just wanted to make sure I covered everything before I spent the money
 

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You can check the signal to the coil with a peak voltage tester - usually about 100 volts from the CDI box to the coil measured between the blk/yel wire and ground
 

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Discussion Starter #7
Ok now I’m puzzled have replaced the stator pulse generator cdi rectifier coil battery spark plug cap. I have also went through the whole wiring harness and rebuilt it. Only thing I haven’t changed is flywheel, has scratch where pulse generator would pick it up would that be enough for it to not send signal
 

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No a scratch on the flywheel is not the problem - what peak voltages are you getting from the components? You could have weak magnets in the flywheel, but there is no test for that.

Here's the 93-00 ignition system
4373


and here's the 01-06 system
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They are basically identical and the stator and rectifier have no effect on the spark except to control engine RPM when in reverse.

To figure out the problem, you have to know the peak voltages.
 
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