RETROFITTING a High Intensity Discharge (HID) headlight kit to a motorcycle is more likely to be tricky than doing the same with a car because of the limited options for mounting the bulky 'ballast' boxes. Most ballasts have short-ish electrical leads, meaning that you can't just stick them under the seat or onto your pillion passenger's lap to get them out of the way. Lengthening the wires would be challenging, because the output leads are a special high-voltage type to cope with the 20,000-odd volts of startup zap, and the integrity of the connectors and insulation is critical, especially when exposed to the weather.
It's worth the trouble. HID technology is similar to that used in street lights, pumping out many times more light than an equivalent wattage halogen bulb, with very little heat. On a motorcycle you have considerably more incentive to avoid other objects on the road than when traveling in a car, and you need all the help you can get to stay out of harm's way. A pile of extra lumens out front is one of the best safety mods you can make.
Standard HID kits consume only 35 watts of power yet produce around three times as much light as your standard halogen bulb. 55-watt HID kits are that much brighter again. HID lights have an added bonus for motorcycle applications in that the bulbs use an electrical arc rather than a white-hot filament, making them far more resistant to vibration. They last many times longer. However, HID lamps run at very high voltage, especially when starting up, so they require a special step-up transformer to convert the native 12-volt power into something much higher. This is the job of the so-called ballast.
If you have a choice when purchasing a kit, buy one with a colour temperature of 6000K. This is about the same temperature as the sun's surface and will turn night into pure white daylight. Bulbs with higher colour temperatures are just gimmicks, wasting energy in the blue and ultraviolet part of the spectrum. If you buy one of these kits, you should also add coloured LED strips under your bike's bellypan, and hang fluffy dice from the mirrors.
Bulbs at 5000K or less will produce a 'warmer' light closer to that of incandescent bulbs, which I presume would penetrate fog slightly better (fog lamps are yellow because yellow light is dispersed less by water droplets in the air). But 6000K produces a clean, stark white that really stands out, even in full sunlight.
You do have to be very careful to get the low beam aimed correctly to avoid blinding oncoming traffic. Glare is a big issue with HIDs, especially retrofit kits, which tend to produce a less-distinct cut-off line on low beam. It's even a legal issue in some countries. Please be conscious of this problem and do your best to minimise any adverse effect for other road users. Personally, I find it very disconcerting to be flying blind through the wilderness at high speed because my eyes have been dazzled by somebody else's lights. We don't want the cops cracking down on us either. It's important to keep your headlight lens clean to reduce glare. In some countries, HID headlights are only legal when factory-fitted in vehicles with automatic headlight cleaning systems. Polycarbonate headlight protectors will make things worse, so substitute a wire mesh one if possible. If oncoming drivers keep flashing you, take it as a message that you need to revert to halogen on the low beam. I haven't had it happen yet, but I did choose to tweak the way my bulbs were seated against the reflector to accentuate the difference in aim between high and low beam (described later).
Another quirk to be aware of is that HIDs take a few seconds to come up to full brightness when cold. This is not a problem on machines like the GS, whose low beam remains on at all times. But on other bikes, where you lose the low when switching to high, you'll have a brief transition time of comparative darkness. Some people consider HIDs to be unsuitable for use on high beam for this reason, but kits have improved in this respect. Newer kits brighten more quickly. My high beam is dim and bluish for a few seconds only if it has been off for quite a while. The bulb stays warm and comes back brightly following most encounters with an oncoming vehicle.
You do tend to lose the ability to flash oncoming traffic as a warning. I notice that my kits produce a quick strobe-like flash when switched on from stone-cold, which might be noticed, but would probably be too fleeting for an inattentive driver to be sure about.
Getting down to specifics
The following is based on my experience with the BMW R1200GS and a double 55-watt H7 kit from eBay that uses relatively large ballasts. More recent kits offer ballasts that are more compact, and should be even easier to fit. Much of this guide will be applicable to other BMWs of a similar vintage to mine and will hopefully even provide owners of other brands with food for thought.
Certain HID kits (perhaps earlier designs interacting with earlier bike firmware) will reportedly require a messy relay and resistor fudge to work correctly with the BMW CANBUS system, but I was happy and lucky to find that this kit plays perfectly with the GS's electronics, with no errors reported. In other words, the CANBUS thinks that the halogen headlights are still in place when it does its startup check. Whew.
I've also heard that some kits can be quite noisy. When testing this kit on a car battery, it did produce a noticeable mild buzzing, but mounted on the bike it is completely imperceptible, and certainly nothing you would ever recognise with the the engine running.
The GS has a little free space along the sides of the front 'beak' where you might be able to squeeze compact ballasts in with a bit of fiddling and customising. See this page for example. However, the bomb-proof ballasts in the kit I bought were just a fraction too large to comfortably fit there, I didn't want to make complex carrier brackets, and I preferred not to compromise airflow out through the vents, potentially sending a bit more hot air from the oil cooler towards the rider. I assiduously examined every possibility around the front of the beast to find potential sites for the ballasts. After several false starts (most of the seemingly free space is needed by the forks as they swing around and bounce up and down), I came up with a relatively simple solution.
If you are prepared to make two very simple brackets out of small lengths of flat-section aluminium (which you can find in a hardware store), and if you can relocate the horn slightly, an ideal place for both ballasts on the 1200GS is directly underneath the steering head. This is a good position to add weight to a motorcycle too—well forward but not outrigger.
First course: spaghetti
Another downside of such a retrofit is that you've got to route wires through the back of the headlight enclosure. In the case of the GS, the original design is very neat with the wiring and bulb connectors hidden away inside the enclosure. You access the two bulbs via screw-on plastic dust covers, shown in these enlargable pictures. Unfortunately, we've got to butcher the two dust covers to run power to and from the ballasts. The good news is that the hole cut in the dust covers is the only lasting modification, meaning that you can easily undo your work by procuring a couple of new dust covers. I've heard they're not expensive. I suppose you could even stick blank grommets in the holes too.
The kit I bought came with two beautiful silicone grommets that perfectly matched the circular indentation of the GS dust covers. Maybe your kit will be so helpful. Whether they are supplied with your kit or not, you will need a couple of rubber grommets to make a neat job of it (available from electronics supply shops, for example) by passing four wires through each of them. Once you know the size of your grommets, you can drill out the dust covers using a holesaw of the same size as the grommet's inner diameter. Start with small pilot holes to make sure that the holesaw doesn't drift. If you don't have a suitable holesaw, a flat-blade drill of the kind used for timber might work, or even a series of small holes around the perimeter of your intended circular cutout followed by some thoughtful whittling and filing.
This picture shows the grommet that came with my kit and the high-voltage wires passing through it, as supplied. But for this application, we also need to pass the low voltage wires through the grommet. You can see the blank nipples in the grommet where the manufacturer has anticipated that you might need to do exactly this, but to get the wires through you need to either cut the wires or pull the connectors off. I elected to do the latter, and to solder them back in place.
My kit came with a double-spade connector that effectively mimics the two prongs of the original H7 halogen bulb. This becomes the source of 12-volt power for the ballast, feeding right off the original bulb connector (which in the case of the GS, is hidden in the headlight assembly, hence the need to feed power first out of the enclosure, then back in).
First, I pulled the spades out of the plastic block by pressing a small screwdriver blade against the barb that holds them in place. The picture here shows one spade connector removed. Then I just pulled the spade terminal off the wire using a vice and pliers, poked each wire through the grommet, soldered the wire back onto it's spade connector, and reassembled them into the black plastic holder.
You can, of course, crimp new spade connectors onto the wires if you have them on hand. I didn't, and soldering makes for a better connection anyway. You can also omit the black plastic holder, and use naked spade terminals, but make sure they can't short out against each other...
To save some grief, try fitting the grommet to the dust cover before doing any soldering or re-crimping. This will save you having to pass the big inline connectors through the holesawed opening. I forgot to think about this ahead of time, and found that one of the connectors didn't quite fit. I ended up saying some bad words while flicking molten tin out of my spade connectors before re-soldering them less neatly than the first time. Worse yet, I made exactly the same mistake when wiring up the second light, and actually found that the big connector could indeed be forced through if turned around backwards, but only just.
The plastic connectors used in the kit that I purchased are fancy items with multi-lipped silicone weather seals. The whole deal is claimed to be water and shock proof. It certainly looks it, but time will tell.
Continued: Part 2