I recently replaced the halogen 55/60w H4 bulb in my 1985 K100 with:
https://www.ebay.com/itm/H4-HB2-9003-920W-138000LM-Fanless-CSP-LED-Headlight-Kit-Hi-Lo-Power-Bulbs-6000K/112562860026?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649Price was right. Came with absolutely no instructions. I think there is a left and a right mount included.
The orientation of the filaments with respect to vertical and focal point is adjustable, if you can find a microscopic allen wrench to loosen and tighten the allen screw which is the size of one #8 birdshot. Vendor, in the interests of customer service, could have at no cost included a proper allen wrench or at least a mention of its size.
I thought the stock 55/60w H4 had good spread and cutoff, low beam was adequate, but needed more illumination for distance on high beam. The headlight fixture is a good one.
The led is brighter, after adjustment of the leds along their longitudinal axis, on high beam than is the halogen. The color is 6000k, which for me is too white/blue. I prefer the halogen's color.
The led low beam close-in illumination is barely equal to the halogen, and its color renders objects it illuminates less remarkable, to me, than the halogen. One of the first few times I rode the bike with the led on low beam, one car from a side street pulled in front of me, obviously didn't see me. A couple hours later at dusk, a pickup truck ran a stop sign to enter the four-lane highway, saw me at his last moment, and slowed. I had both tires skidding on the K100. I think the moral is to use high beam led during daylight hours. Low beam seems visible enough after dark.
The led bulb does fit in front of my fairing mount.
The K100 fixture which receives the bulb is some sort of plastic. I was apprehensive the 80/100w halogen I put in my R100 bike would melt the K100 fixture. The 80/100w bulb does a good job in the R100 fixture.
This bulb has received good reviews in H4 fixtures.
https://advrider.com/f/posts/36565431/