CDI Testing By Guitarman (Read 1,390 times)

[Guitarman]

Is there a way to test a CDI off the bike? Or does it need power to be tested?

[tvnacman]

I test them , by plugging them and starting the engine give it a quick rev listen to the decell then turn the key off . If it shuts off its good . I also listen to start up I will check a few with a timing light , the variable timing cdi's are all checked with a timing light they take a little longer .

John

[poppajon]

A cdi must be connected to a magneto to see what it does. YOU HAVE TO HAVE INPUT TO TEST FOR OUTPUT !!!

[Alleyoop]

Jul 25, 2014 23:51:57 GMT -6 Guitarman said:

Is there a way to test a CDI off the bike? Or does it need power to be tested?

That's like a trick question, explain what problem your having it may have nothing to do with the CDI.

To correctly test a CDI you need special equipment, but you can do some testing to come to a intelligent and logical decision that the problem is MOST likely the CDI.
Alleyoop

[Guitarman]

I'll let you know in a few days. I'm waiting on some parts right now and when I get them in, I'll be checking the CDI.

[Bashan]

Actually you can do a little multimeter testing on them and get a little information. First here's testing an AC CDI (purple) and a DC CDI (black). There's been discussion off and on about whether the two ground ports were any different on the same CDI. The two ports have continuity so NO, they are both grounds for the CDI and either can be used. DC:

AC:

You'll find diodes too as electron flow is directed for the capacitors. There's oddly some between the killport and power port on the AC but no readings on the DC:

And one between the power port and the ground:

Both of those blocked with no voltage the other way (normal).

While the DC showed double the voltage:

The heart and soul of a CDI is the capacitors as they store electricity for the discharge. Without knowing the specifics on the capacitor the testing is vague. But with a multi set to capacitor the reading should start out low, slowly build, and then discharge. If it won't build it's a bad capacitor and just one will do your CDI in.

So you can get a little off of the meter but it is correct there's special instruments to test them and there's always swapping out. Rich