I am having the exact same problem... one spark..Did you ever fine the problem? I have gone over the entire bike and cant find where it issue is coming from. I have taken off the regulator to see if I can get and ohms from it and am getting nothing, the above comments said the the bike will run with out it, so should I even keep
messing with it? does any one know a test for it I cant find it in my manual.

 

The regulator/rectifier has nothing to do with spark. Only the charging of the battery and lights. It will start and run fine without it, but you will have no lights and your battery wont charge. If your battery charges fine, and the lights work without a battery installed, it is fine.
From what I've read, the most common no-spark problem on the Big Reds is a bad exciter coil, its easy to check like I said above. Once you eliminate that, all thats left is the coil or CDI. The resistance of the coil is also easy to check. I would check that second.