A "HID kit" consists of HID ballasts and bulbs for retrofitting into a halogen headlamp. Often, these products are advertised using the name of a reputable lighting company "Real Philips kit! Real Osram kit! Real Hella kit!", to try to give the potential buyer the illusion of legitimacy. Reputable companies like Philips, Osram, Hella, etc. never endorse this kind of hacked usage of their products.
Nevertheless, it's easy to get "HID kits" from China bearing the (unauthorised, counterfeit) brands of major, reputable companies. See the link below for just a few examples of the many packaging options offered by just one Chinese maker of "HID kits".
http://www.webcitation.org/5mc0CuxTZ
Halogen headlamps and HID headlamps require very different reflectors and optics to produce a safe and effective (not to mention legal) beam pattern because of the very different characteristics of the two kinds of light source, glowing filament VS arc.
When designing the optics (lens and/or reflector) for a lamp, the characteristics of the light source are the driving factor around which everything else must be engineered.
If you go and change the light source, you've done the equivalent of putting on somebody else's eyeglasses: You can probably make them fit on your face OK, but you won't see properly.
The only available HID lamps have a longitudinal arc, arc path runs front to back on the axis of the bulb, but many popular halogen headlamp bulbs, such as 9004, 9007, H3 and H12, use a filament that is transverse (side-to-side) and/or offset, (not on the axis of the bulb) central axis of the headlamp reflector). In this case, it is impossible even to roughly approximate the position and orientation of the filament with a "retrofit" HID lamp.
Just because your headlamp might use an axial-filament bulb, though, doesn't mean you've jumped the hurdles—the laws of optical physics don't bend even for the cleverest marketing department, nor for the catchiest HID "retrofit" kit box.
A relatively new gimmick is HID arc capsules set in an electromagnetic base so that they shift up and down or back and forth. These are being marketed as "dual beam" kits that claim to address the loss of high beam with fixed-base "retrofits" in place of dual-filament halogen bulbs like 9004, 9007, H4, and H13. A cheaper variant of this is one that uses a fixed HID bulb with a halogen bulb strapped or glued to the side of it...yikes!
What you wind up with is two poorly-formed beams, at best.
The reason the original equipment market has not adopted the movable-capsule designs they've been playing with since the mid 1990s is because it is impossible to control the arc position accurately so it winds up in the same position each and every time.
As if the optical mismatch weren't reason enough to drop the idea of "retrofitting" an HID bulb where a halogen one belongs—and it is!—there are even more reasons why not to do it.
The most dangerous part of the attempt to "retrofit" Xenon headlamps is that sometimes you get a deceptive and illusory "improvement" in the performance of the headlamp.
The performance of the headlamp is perceived to be "better" because of the much higher level of FOREGROUND lighting, on the road immediately in front of you, the driver.
However, the beam patterns produced by this kind of "conversion" virtually always give LESS distance light because of the bad focus, and often an alarming lack of light where there's meant to be a relative maximum in light intensity, that’s further away.
The result is the illusion that you can see better than you actually can, and that's not safe.
It's tricky to judge headlamp beam performance without knowing what to look for, because subjective perceptions are very misleading.
Having a lot of strong light in the foreground, that is on the road close to you and out to the sides, is very comforting and reliably produces a strong impression of "good headlights".
The problem is that not only is foreground lighting of decidedly secondary importance when traveling much above 30 mph, but having a very strong pool of light close to you, the driver, causes your eyes iris to close down, WORSENING your distance vision...all the while giving you this false sense of security. This is to say nothing of the massive amounts of glare to oncoming traffic that back dazzle to you, the driver, that results from these "retrofits".
HID headlamps also require careful weatherproofing and electrical shielding because of the high voltages involved, ~25000 volts.
These unsafe "retrofits" make it physically possible to insert an HID bulb where a halogen bulb belongs, but this practice is illegal and dangerous, regardless of claims by these marketers that their systems are "beam pattern corrected" or the fraudulent use of established brand names to try to trick you into thinking the product is legitimate.
In order to work correctly and safely, HID headlamps must be designed from the start as HID headlamps.
Marketers will always be coming up with dazzling new pseudo science, tempting new hype and sneaky new ways of trying to convince you to buy their stuff. It's what they do.
This article will never go out of date, because the problems with HID kits are conceptual problems, not problems of implementation, therefore, they cannot be overcome by additional research and development.
Please note: The above article is not mine, I’m not a light expert in any way but after reading it I was start wondering and made my own tests which confirmed the above, and this is the purpose of it.
I think it deserves a thread of its own rather than just a link that most won’t click on it.
Below are some bulbs I have tested on my bike, OEM, Phillips MotoVision (the orange tinted "Be Seen" stuff), Phillips XP ExtremePower, Bosch PnP HID's and some LED's for rear drive/stop, repeaters and license plate. I also tried some bluish Xenon filled 100W bulbs but they were keep blowing fuses. I got the best results with an Osram NightBreaker, that's a 60/55W with 90% claimed more light output and 10% whiter color, I also changed the headlights cabling with lower gauge (thicker) ones which also helped quite a bit.
Another thing that helps very much is an easy conversion in the left hand high/low beam switch, this conversion keeps the low beam still ON when switching from low to high so you have both beams on, really helps the view on the road at night. Low beam is still just low beam and the flash to pass switch works as normal.
The conversion is described step by step on the following link:
749/999 Headlight Mod
As you can see there are solutions and that "price + shipping lower first" HID conversion kit that is constantly on sale in Ebay might not be the best one.
Linear Mode
