2020 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.

K Bike H4 Headlight Bulb "Shootout"

2021 Update- LED H4 Headlight Bulbs

As somebody who likes to ride at night, getting a lot of good light on the road ahead of me matters. I decided to conduct a headlight "shootout" against my garage door comparing four different H4 bulbs side by side.

Headlight Relays: LED headlights use less power than a standard filament bulb, roughly 25 watts vs. the 60/55 watts of a standard bulb. Part of the reason that it's advisable to use headlight relays on a K is to prolong the life of the headlight switch so that all of the headlight current isn't going through the switch. Therefore headlight relays aren't as necessary when using an LED headlight.

However, the other reason for installing headlight relays is to upgrade the wire gauge so that the headlight gets a slightly higher voltage. So if you have the inclination to do so then adding headlight relays for an LED headlight isn't a bad idea.

The test:

I tested four different H4 bulbs:

Factory 60W/55W: This is the bulb that came on K Bikes from the factory.

"Xenon" 60W/55W: These are inexpensive Chicom H4 bulbs that can be had on Ebay for about $8/pair. They are whiter than the factory bulbs.

"Xenon" 100W/90W: Same as above but in higher wattages. Note that the higher wattage is technically illegal but since K bikes have a good low beam cutoff they don't blind oncoming traffic and they don't scatter light like real HIDs which are not designed to run with a regular H4 reflector and lens. Warning: Do not run higher wattage bulbs like this unless you've upgraded the wiring and added headlight relays. (Link to headlight relays page.)

LED H4: H4 LEDs were pretty much garbage for the first few years but lately there are a lot of decent ones on the market. LED headlights generate a fair amount of heat and therefore require a built in fan to cool them.  Many LED H4s have a "huge" fan on the back so you need a lot of clearance behind the headlight and a mounting system that will go around the fan. Early K bikes have a mounting ring with a 31mm hole and most of the LED headlight bulbs with big fans on the rear are much bigger than that.


K bike H4 mounting ring:

Therefore I decided to try an LED H4 that has the fan built into the body of the H4 that requires less clearance and will fit inside the mounting ring:

If you're looking for an LED headlight that is known to work in K bikes you can find one here:



This is a very rudimentary testing regimen.  I did this about 15 feet from my garage door with no light measuring instruments aside from my point-n-shoot camera and my eyeballs.

Here's a picture of my elaborate testing facility. A couple of identical RS/RT/LT headlights and a new, fully charged Odyssey battery. Both headlights are hooked to the same battery at the same time with identical length and gauge wiring so that both headlights get the exact same voltage.


The Results - Side By Side Comparisons

1A: LED vs. Factory - Low Beam

1B: LED vs. Factory - High Beam

2A: LED vs. Xenon 60/55 - Low Beam

2B: LED vs. Xenon 60/55 - High Beam

3A: LED vs. Xenon 100/90 - Low Beam

3B: LED vs. Xenon 100/90 - High Beam

4A: Factory vs. Xenon 100/90 - Low Beam

4B: Factory vs. Xenon 100/90 - High Beam

5A: Xenon 60/55 vs. Xenon 100/90 - Low Beam

5B: Xenon 60/55 vs. Xenon 100/90 - High Beam

6A: Xenon 60/55 vs. Factory - Low Beam

6B: Xenon 60/55 vs. Factory - High Beam


My Wholly Subjective Observations

There are lots of H4 LED headlights on the market these days.  I do not have the time, money or inclination to test them all. The one that I did choose fits well in K bike headlights does a very good job.

As you can see in the pictures, the LED puts out whiter light than any of the other bulbs.

The LED H4 has a nice bright well-defined beam with no light scatter. The tight beam helps put more light farther down the road for riding at night with the high beam on.

The fan in these LEDs is really quiet. I was barely able to hear it when doing my tests.  Even with the engine off you probably won't hear it when it's buried inside the fairing in the headlight.

March 2021 update: I've been running the LED H4s in both RS/RT/LT and K75S headlights for a while now and am quite pleased with how well they work.


If you've had experiences with other H4 bulbs, especially LED, then please let me know and I'll add your comments to the bottom of this page for others to see.

Email: smithduck@gmail.com


2020 Drake Smith - Please do not use or reproduce this elsewhere.  Feel free to link to it though.