This is another question that gets asked a lot so I'll add it to the FAQ
There are two plugs on the CDI; a four pin plug and a two pin plug. Look at the two pin plug. If there are two wires coming out of it, you can use an XRL CDI. If there is only one wire coming out of it, you cannot.
The second wire on the two pin plug is used for safety reasons on some Honda models. On these models, this pin needs to be grounded for the CDI to work. On the XR650L (XRL) this is used for the kickstand switch. If the kickstand is down and you click the bike into gear, this wire looses it's ground and the CDI stops working which kills the engine. The US NX650 did not have a kickstand switch, so the NX CDI did not require this pin to be grounded for the CDI to work. Since it wasn't required, Honda did not bother to run a ground wire to this pin on some of the NX's, but on others they did. My official Honda wiring diagram shows that this ground wire should be there even though it was never installed at the factory on my bike ('88 US model NX650).
If you only have one wire and need to replace your NX CDI, here are your choices:
1) Find an NX650 CDI - I found an online store a while back that sold reconditioned NX CDI's for about $70, but I can't seem to find the site again. I'll keep looking. If anyone else knows where to find these, please let us know.
2) Run a ground wire to the extra pin - you have two choices here:
A) Find an old Honda wiring harness - Honda used this style CDI plug for many different models. Get your hands on a harness with the right plug (eBay, etc.), cut off the plug but leave a long section of the two wires attached. Splice it into your NX harness. On the four pin connection there is also a ground (green wire). You can splice the two-pin ground wire right into the four-pin ground wire (this is how it is wired from the factory for models that have the two-pin ground connected. At one time I plugged an XRL CDI into my NX so I did this modification to get it to work.
B) Find new wiring components - Cycleswareables.com carries many different electric connectors
. The site is not very user friendly. I believe the plug is an FRS series, part number FRSY-107 (cyclewareables PN CW34-0283KL), the pins would be FRS-102 (CW34-9296KL), and the boots should be FRS-103 (CW34-9297KL). You will also need a crimping device that fits these pins (probably a Molex style crimping device). I haven't tried this method so I really don't know how reliable these part numbers are. If you try this, please let me know how it works out.