I though I'd share this. A while back, I replaced my M70 stock sealed beam lamp with an H4 kit. Its pretty crowded inside the cone, but I made it work by leaving out the big rubber seal. http://sovietsteeds.com/forums/viewtopic.php?f=23&t=38476&hilit=headlight
That was about a year ago, and Its been working great.
I'm an LED nut though, and have been wanting to try one out. I recently got my old Cyclops flashlight working, which just happens to take an H4 bulb, so I thought I'd start with that. The LED I decided to start with is made by Cyron http://smile.amazon.com/gp/product/B00REQVA34?psc=1
At 12v, the regular H4 uses 4.5A (55W), or 5A (60W) High beam.
At 12v, the LED uses 1.2A (15W), or 1.8A (22W) High beam.
High beam info doesn't seem available, but the light uses 2 LED chips for low beam, and lights up a third for high beam. I assumed that each chip uses the same amount of power.
The lamp came with 4 adapters to fit multiple types of light bulb. I picked the one that matched the H4 shape, and it all went together fairly well.
It has a heat sink and fan on the back, which takes up more room than the standard bulb, but the plug is on a cable, instead of attached at the back, so that helps.
Looking at the light patterns, keep in mind this is a basic flashlight reflector, not a fancy headlight diffuser. So actual results on the bike may vary.
What I noticed was that the LED on dim was significantly brighter than the H4 on dim.
The LED on bright though, was not much brighter than the LED on dim.
Both bulbs on dim showed a bright half-circle in the periphery below the central bright spot.
The LED had a higher than center bright spot than the H4 on dim.
The H4 on bright seems to me, about the same brightness as the LED on bright. Though, the LED is whiter, and has a larger central bright spot.
Both peripheral areas were large and fully circular on bright.
I've heard from several sources that LED Headlights are disappointing as far as the bright setting, and that the headlight angle may need to be moved down to compensate for the different beam pattern. I'd agree the light will probably have to be adjusted down when I get this on my bike. As for the disappointing bright setting, I'd say the issue lies with comparing the LED dim to the LED bright. The LED dim is much brighter than the H4 dim, but the two bulbs on bright seem about the same to me. Except for color.
At some point I'll strap this on my sidecar and do a comparison between it and the actual bike headlight.