CDI compatibility

Hi, I want to ask if a cdi model 2008 would fit to the model 2004 or so say what would be compatible on 2004. I want to replace it because in this cdi the command for taillight broke. Thanks.

Hi, I want to ask if a cdi model 2008 would fit to the model 2004 or so say what would be compatible on 2004. I want to replace it because in this cdi the command for taillight broke. Thanks



On the 2004/2005 model years, the positive lead of the tail light is connected to the main relay, which is activated by the CDI box upon starting the bike.  That being said, I would check your main relay to see if it has gone bad.  The CDI box may be just fine.  In fact, I would bet your problem is the main relay.  The CDI box uses solid state components whereas the relay is mechanical and therefore prone to wearing out over time.  If it turns out being the CDI box, then rather than replacing the box, it would be MUCH cheaper to simply disconnect the positive wire from the main relay and install a switch between the tail light and positive battery terminal.  The only issue with doing this is you'd have to remember to turn the switch off after turning off the bike, or you risk draining your battery.


For those of you familiar with the 2004/2005 wiring, from the diagram, it appears that the only purpose of the "main relay" is to switch power to the tail light.  Is this correct?  If so, it seems a little overkill.  There must be some other reason for using a relay.  My best guess is that the relay is more for accessories connected to the "option" connector.

Edited by mossman77

It will fit but  control of DC is different between the two modules so you may need some wiring changes.  The 04-05 controls tail/fan DC by grounding a relay, the 06+ controls the tail light ground wire. So different wiring harnesses.  Check the part numbers of the ignition modules to see if they are the same.


When you say command do you mean the tail light doesn't work? I would suggest some trouble shooting before swapping out modules.


Component locations:

The relays and ignition control module are behind the left side number plate:

The ignition module is on top of the air box near its forward edge, next aft is the starter relay (having two large red cables going to the battery and starter).  Aft of the airbox is the main relay.

The connector for the fan is inboard of the right radiator.

The rectifier/regulator is inboard of the left radiator.


The main relay controls DC power for the taillight/fan and gets power from the same wire in the harness that provides power for the start button, so if the estart works the relay is probably getting power.


The red wire to the main relay should have battery voltage.

The black wire from the relay provides power for the tail light and fan when the engine is running, if the relay functions.

The green wire from the relay goes to the Ignition Module, which it connects it to ground when the engine is running to operate the relay.


The Owners manual has a wiring diagram as do the Shop Manuals.

The main relay controls DC power for the taillight/fan and gets power from the same wire in the harness that provides power for the start button, so if the estart works the relay is probably getting power.



Just to clarify for the OP, even if the relay is getting power doesn't mean it is working.  You need to test to see if the CDI box is providing a switched ground to the green wire while the bike is running and also that the relay is outputting 12V on the black wire (also while the bike is running).  If you get a good signal from your CDI box but no output from the relay, then the relay is bad or the contacts are dirty.  If you don't get a signal from the CDI box, then your CDI box is to blame.  If it turns out being the CDI box, I would personally just re-wire the tail light, which would be pretty simple.  Let us know when you get to that point and we can go from there.

Edited by mossman77

Thanks for the clarification, this is defective CDI sure because I have two identical motorcycles since 2004 and I did all the tests possible to find the problem does not tail light . I studied and I suspect cdi scheme but was tried last component. I found one for sale on ebay but it was the model 2008 I asked to know if this would work. There is also another reason to change cdi because the plugs are destroyed when acid was the former owner. It has invested a lot in this motor around $ 2500 and is the only thing that is not working.
PS  with other cdi the tail light work. I watch until I find one good sale.


I am attaching two pictures of brothers.



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