The 2 plug 6 wire CDIs come in two different designs. One is powered off 12 volts DC, and the other is powered off a moderately high voltage AC which comes from the stator. Unfortunately there is no reliable way to tell the difference between the two by just looking at them. To be sure you need to use a meter to find out which you have:



1) Unplug the CDI, and turn on the ignition. Do not crank the starter motor. Use a meter to measure the *DC* voltage on the pin labeled "AC ignition power" in the wiring harness to the ground pin in the same connector. If you measure 12 volts DC then you have a DC powered CDI.

2) If you don't measure 12 volts DC on the ignition power pin, then switch the meter over to measure AC volts on the 200 volt scale. While cranking the starter motor, measure the AC voltage on the "AC Ignition Power" pin to the the Ground pin. You should see 40 to 80 volts AC. If you measure AC voltage when the starter is turning then you have an AC powered CDI.

Using a meter is the only 100% reliable way to figure out if your CDI is AC or DC powered. But there are some clues you can use that are usually (but not always) correct:

A) DC CDIs tend to be a little larger than their AC powered counterpart. This is because the DC powered CDI needs a bunch more circuitry to convert the 12 volts DC to the moderately high voltage supply that CDIs must have.

B) Most (but not all) DC powered quad ignition systems do not use the kill switch input pin. The CDI connector pin usually has no wire tied to it. AC powered quad ignition systems usually do use the kill switch input pin.

To troubleshoot no spark problems on a 6 pin AC powered CDI it makes sense to start in the middle (the CDI), measure as much as we can and branch out from there. For the CDI to do its thing it needs power, a trigger pulse, and it must must be inhibited via the kill switch input pin.

1) Unplug the CDI. Turn the ignition switch on. Set all kill switches the the "run" position. In the wiring harness, measure the resistance of the kill switch pin to the ground pin on the 20K ohm scale. It should read infinite ohms (same as when the meter leads are hanging free and not touching anything). It should not read zero ohms (shorted).

2) Leave the CDI unplugged. Use a meter to measure the resistance of the AC ignition power pin in the wiring harness to the ground wire on the 2K ohm scale. You should read approximately 400 ohms. What do you measure?

3) In a similar fashion measure the resistance of the Ignition Trigger Pulse pin to the ground pin. You should see 150 ohms or so. What do you measure?

4) Switch your meter over to measure AC volts on the 200 volt scale. Leave the CDI unplugged. While cranking the engine, measure the voltage on the AC Ignition Power pin in the wiring harness to the ground pin. You should measure 40 to 80 volts AC. What do you measure?

5) Set your meter down to the lowest scale you have for measuring AC volts. 2 volts would be ideal, but some meters don't go that low. In that case use the lowest scale you have. While cranking the engine, measure the voltage on the Ignition Trigger Pulse pin in the wiring harness to the ground pin. You should measure 0.2 to 0.5 volts AC. What do you measure?

6) Now plug the CDI back in. Measure the AC voltage on the Ignition Coil pin to the ground pin using the 200 volt scale. If you have to, use a sewing pin to poke through the wire insulation and then put the meter probe on the sewing pin. But don't hold your fingers on the connection during the next test - there may be high voltage here when the engine is turning. With the ignition on and all kill switches set to the "run" position, crank the starter motor. You should see voltages bouncing around at random values and the meter captures all or part of a spark event. What do you see?