No spark, trying to troubleshoot CDI or Magneto

[relaxxx]

The first thing I did was try a new plug, no spark.
I tested magneto wires, 330 ohms between black and blue. 2.5 between black and white. This seems to be on par with a good magneto.

I can't find any readings on the CDI between black and blue, nothing readable testing the screw side, numbers jump like trying to read a capacitor.

I read there was supposed to be 75V AC output on magneto black and blue wires. I could only read about 12V rolling the bike forward a couple feet. Not sure if this means It's bad or my digital meter just isn't accurate or if I'm even testing it right because it's just a quick pulse? I did hook some LED lights to the black and white and they did flash when motor turned. Also hooked same LED's to black and blue and LED's flashed very bright.

Is there any test I can do with the CDI? Should I just bite it and order both replacement parts?

 

[Junster]

Have you really checked out the plug wire? Try unscrewing it from the cdi and using a automotive wire. Just cut it off clean and push hard as you screw the new plug wire in. Then put the little screw cap back on the plug so it hooks up to the auto style wire. Leave the white wire disconnected till you get it going again. Hope this helped.

 

[duivendyk]

Moving bike back&forth does not prove much, you are getting an output, your blue/blk coil output is OK I think ,Digital meters use sampling this gives erratic readings on fast pulses.If there is some one out there with a multimeter and this type of CDI that WORKS plse measure between plug wire and ground (black). and report.I would expect between 2-10k Ohm.Then you will be able to compare.

 

[relaxxx]

The plug wire is good. I went ahead and ordered a new CDI as this seems to be the most likely culprit. The cheapest I could find was on ebay # 400050335654, it has a green wire instead of blue. Hopefully it will last more than one season. I was just starting to ride again, now I have to wait a week or two.

 

[spad4me]

I have a question?
Did you look in the magneto case to make sure it is DRY???

 

[duivendyk]

Just for curiosity's sake ,do you happen to remember what it read on the plug connection?

 

[relaxxx]

I did look inside the magneto, I first thought the black wire was shorted but after opening the case i realized it's bolted right to the case so black is ground, Nice and dry inside. Plug wire was like 0.5 ohms.

 

[duivendyk]

I meant from plug connection at the plug cap to ground (black) at the CD unit, not from one end of plug wire to the other.

 

[relaxxx]

Oh, I couldn't get a reading, numbers jumping all over the place. Is it supposed to be a certain resistance?

 

[relaxxx]

Well I got my replacement CDI. hooked it up and still no spark. I thought I saw the tiniest spark while rolling fast but it's kind of hard to tell when the only way to test is holding the spark plug against the motor while running beside it like an idiot.

I guess the only thing left to do is replace the magneto. Kissing goodbye another $30 and week of riding!