Ok GJ, let me see if I can tackle this one. Just remember that I by no means am an electrical expert. I still get confused with watts, ohms, and amps as far as what they do.
I beleve that wattage is how much power the appliance pulls. As for the bulb in your bike, it pulls (according to what I'm reading on BB's site) 55 watts on low beam, and 60 watts on high.
Just remember about useing household light bulbs. The higher the watts, the brighter the bulb, but the more power they are going to pull.
Now as for the warning from honda. They might be thinking about the wireing for the light. It might not be reated to handle more then 60 watts. In other words, you try to put (or pull) more then that through it you might heat the wireing up.
Now as far as using a lower watt bulb. I don't think there would be any problem except safty. Being seen and such.
Now, one question. Why would you not want to replace the bulb with the same rated bulb? Bike Bandit has them for only $6.60 which is cheep. Figguring that a 9004 bulb, which I beleve is a hi/low beam hologen that is used on most cars now a days, from Advance Auto Parts is $7.97.
The bulb that honda uses is a Stanley bulb. (What? You thought Honda made their own bulbs?)
It should have the Stanley part number stamped somewhere on it. Take that number and see if your parts guys (or gals) can cross referance it to something that they can get.
If they can't, try NAPA. They have their hands in everything from big rigs to lawn mowers, and their nation wide. I know. I worked for them for 3 years as a parts guy. Beleve me, I've looked up some crazy shi......ok I'll keep it clean.....stuff.
*EDIT*
Just did some checking on Sylvania's website

. Check this out.
http://www.sylvania.com/cgi-bin/MsmG...4&hiword=9004+
Look at the first bulb. That looks a heck of alot like the one that goes in your light. Might be worth checking into.
*Now back to my regularly rambling...LOL*
Buy everything that you've been telling me I think that your going to find that the problem is going to be the conection there in the bucket. Even though the contacts on the back of the bulb may look good, they may be loose and not making good contact with the blade on the bulb. It's either that or what I told you earler with the ground. That's going to be the best place to start anyway. When you start looking into it.
And yet again, always glad to help as much as I can.