I tested four different H4
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.)
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
If you're looking for an LED
headlight that is known to work in K bikes you can find one
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
LED vs. Factory - Low Beam
LED vs. Factory - High Beam
LED vs. Xenon 60/55 - Low Beam
LED vs. Xenon 60/55 - High Beam
LED vs. Xenon 100/90 - Low Beam
LED vs. Xenon 100/90 - High Beam
Factory vs. Xenon 100/90 - Low Beam
Factory vs. Xenon 100/90 - High Beam
Xenon 60/55 vs. Xenon 100/90 - Low Beam
Xenon 60/55 vs. Xenon 100/90 - High Beam
Xenon 60/55 vs. Factory - Low Beam
Xenon 60/55 vs. Factory - High Beam
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
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.
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
© 2020 Drake Smith - Please do
not use or reproduce this elsewhere. Feel free to link
to it though.