I had quite a time with the electronic ignition: sometimes it would fire right up, others there was nothing... no spark. With help from the XS650 crowd, and some interesting methodology for finding the culprit, I determined that there was some sort of intermittent break or no-go inside the TCI box...
There was a lot of voltage- and continuity-testing, and finally got it figgered out... I wrote a thread on the troubleshooting sequence, which is posted on XS650: "How to Troubleshoot the TCI Ignition System".
An interesting thing that I used as a test-light was a 12V LED: because they react so quickly to voltage pulses, they can be used to read the "signal" at the TCI box output, a good thing to know when tracing whether there is a signal coming down the pike to the coils!
And this guy is worth its weight in platinum: a simple spark-indicator which hooks up in series, and flashes IF there is a spark... a LOT easier than pulling plugs and grounding them, and much less likely to cause coil damage than a dicey-grounding of a pulled sparkplug!