To increase the time between battery charges on my 1993 Yamaha XJ600S which no longer charges its own battery, I decided to install LEDs on the front running lights and the tail light, as they will be much less of a drain on the battery. As expected, the running lights / turn signals were much more of a success than the tail light.
The tail light is brighter but very small, given the directional nature of LEDs (particularly the older, bulbous type on this cluster). It was the only option available from superbrightleds.com that also had white LEDs for license plate illumination.
The running/turn signal lights work a charm, and their turn-signal state is much brighter than the incandescent bulb, though the electronic flasher (required to make them flash at a normal rate) takes about a second to boot up and start working. An old scooter I had was like that, and I don't do sudden lane changes anyway, so I'm not too concerned about that.
The tail light, though... I wonder if I should just get a tower type that illuminates in all directions, and dispense with the white illumination of the license plate. It may not be legal, but it would be brighter, even on the plate, I reckon. Maybe someone makes a splitter that would allow me to install two tail lights. There's plenty of room for such a thing in this bike's tail light cavity... (ADDENDUM: Actually once I recharged my battery, I was quite surprised at the tail light. It's still not as much contrast between the two states, but it's close, and the instant-on does make up for it a bit. I'd still prefer a larger cluster -- better yet one with extra LEDs that only turn on with the brake -- but I don't see anyone making one that has white LEDs for the license plate.)
You may be wondering why I didn't change the instrument panel lights to LEDs, as those are always-on too... Well, they're not. Those bulbs burned out several years ago, so they're not draining anything! At night, I have a completely dark dash, and just judge my speed by feel/sound.
Parts used, all available from http://www.superbrightleds.com :
LF1-S-FLAT universal motorcycle electronic flasher.
1157-R19W6 -- 19 forward-facing red LEDs with 6 radially-faced white LEDs
1157-A45-T -- 45 amber surface-mount LED tower