Motorcycle Repair: Honda Rebel Electrical problem, regulator rectifiers, weather subjects

Question
I have a '96 Honda CMX 250 Rebel that is driven infrequently.  It is also exposed to the elements during the riding season.  I now have an electrical problem that I want to pinpoint.  Bike will not crank on start, makes a clicking sound and the lights start to go dim if at all.  I got a brand new battery and it started right up the first and only time and then the same problem.  The only way to get it started now is if I charge the battery and with the charger still connected, push the ignition switch (takes a few attempts).  I notice that once the bike gets going, there is a lag between the time I push the horn and when it actually sounds and the lights seem to dim intermittently.  I was going to perform some voltage tests but I'm not too sure what I would be looking for.  Thank you for any help you can give me.  

Answer
Antonia, you definitely have some charging system issues there...
That you bought a new battery and it immediately went dead, indicates the probability that the regulator/rectifier is probably at fault, however all components should be checked carefully. You have a stator, regulator/rectifier and rotor as primary parts of the system. Rotors on the end of the crankshaft are seldom an issue unless the key shears off and the rotor is just spinning on the end of the crankshaft.... highly unlikely.
Stators are generally reliable, but should be checked for continuity between the windings and that there is not ground path for them to the stator mounting frame.
Regulator/rectifiers are difficult to check with common tools. You can try to check the diodes with an ohm meter to see if some are shorted or open. A shorted diode will drain the battery overnight.
Leaving a bike out in the weather subjects the electrical connectors to corrosion, so they should all be checked for any connection issues.
More troubleshooting info at www.electrexusa.com
Register at http://www.powersportspro.com/partsfish/login.asp
and check the Rebel microfiche online to see locations of the components. Otherwise, get a shop manual from a dealer or on Ebay.
Bill Silver