The 1988 Honda Transalp has a single headlight which supplies the high and low beam. It uses a standard H4. I think the low beam is acceptable. But the high beam throws the light long and narrow. You have trouble seeing the side of the road and what is close in front of you.
Changing the bulb to a higher wattage is not recommendable, unless you upgrade the wiring at the same time. You can however put in a more efficient bulb. Like the Philips X-treme or Osram night breaker. These can offer a slight improvement.
Another option is retrofitting a HID-kit. There are some problems with that. This solution is not legal in a lot of places and you often send a lot of glare to oncoming traffic. The beam pattern wont change, so it doesn’t address my main concern. But you will get a lot more light from these kits.
Since I had a LED light bar laying around I mounted it on the bike. I placed it on the stem, so when the handlebars turn, so does the LED bar. Since it had a low current draw I could connect it straight to the original wiring without any measurable voltage drop at the bulb. The LED was bought at dealextreme.com. And here is a link to the product.
It added the lighting close and wide. This was a good combination with the original high beam. But the light output (lumen) was to low. It was specified at 1440 lumen, but I’m guessing it gave about 1000.
If purchasing an extra light for night time usage I would recommend getting something with a higher output.