Shop Talk | Driving Light Install

“If it weren’t for the dark I’d really like riding at night.”

Installing a set of accessory spotlights is a practical and aesthetically pleasing way to enhance your cruiser’s appearance, as well as augmenting its OEM lighting. It’s also a relatively inexpensive upgrade, easily performed by anyone that can follow written directions. Nevertheless, like any project that involves moving electrons from end of the bike to another, it must be done properly, or there’s bound to be tears.

Stylistic considerations aside, spotlights fall into four broad categories: Fog lights; driving lights; long-range lights; and flood lights. Since the last two are for specialized applications, like off-road racing and nighttime construction work, we’ll concentrate on the ones most typically used on motorcycles; fog and driving lights.

As the name implies, fog lights are designed to illuminate the road under adverse atmospheric conditions, in particular when rain, snow, dust or, yep, fog, makes it difficult to see. Typically, fog lights produce a beam that’s between 35° and 50° wide, though some of the more aggressive fog lights can reach 90°, and go roughly the length of your standard low beam, though some of the high power ones can extend up to 600 feet.

Because fog lights produce a wide, short, beam pattern, their light isn’t reflected back at you by airborne particles (at least not when they’re properly mounted), so for optimal effect, fog lights should be mounted as close to the road as practical and wired to work in conjunction with your low beams. As a side benefit, the wide light of a fog lamp helps illuminate the edges of the road, especially in corners and tight bends, which makes them just as handy on clear nights.

_…while fog lights are great on those nights when fog comes creeping in, they're not nearly as useful on clear nights when you want to howl at the moon, or just get where you're going without wadding yourself up on some murky road.


Driving lights are used to supplement your OEM high beam. As such, they project a longer, brighter—though somewhat narrower—beam than fog lights. Many of them can project a 20° beam over a mile, and some can produce 170 watts of power, though lights of that intensity aren’t intended for street use.

Driving lights work really well at illuminating distant objects, and they’re also pretty good at blinding oncoming drivers, so if you decide a pair of Retina-burner 1000s are they way to go, use them with some consideration. Driving lights can be mounted just about anywhere you have room for them, though higher is always better and legally, they have to be dimmed with the high beam, so properly installed ones are always wired to work only in conjunction with the high beam.

There are also some dual-filament versions, like the PIAA 525 series, that incorporate a fog and driving function in one light, which comes in handy when mounting space is at a premium or you just don’t want to clutter up your bike with a lot of lights.

Picking the right lights takes some consideration, and obviously, for the majority of us, that includes the aesthetics. Since that’s an entirely subjective thing, I’m not going to comment, except to say choose wisely. Bling is as out of place on an adventure bike as a set of 8 1⁄2 -inch rally lights would be on a cruiser.

First, consider what type of lights will do you the most good. Under most circumstances, I prefer driving lights to fog lights. As I mentioned, while fog lights are great on those nights when fog comes creeping in, they’re not nearly as useful on clear nights when you want to howl at the moon, or just get where you’re going without wadding yourself up on some murky road. But who knows—maybe you spend a lot of time riding across the moors on damp nights, or live in Seattle, in which case fog lights might be the better choice.

If you decide on fog lights, I’d recommend avoiding the traditional amber lens versions. Without entering into a lengthy debate on their effectiveness during inclement weather, I can tell you that many manufacturers are moving away from amber because it reduces the amount of available light on clear nights.

Once you’ve settled on a type of light, check the fine print to ensure it’s compatible with your bike’s electrical system. What you need to know is how many watts of energy the lights use, and how many watts your charging system has to spare. If the former is less than the latter, all is well. If not, look for another set of lights.

The math is simple. Your shop or owner’s manual should list the alternator’s maximum output in watts. Understand that this is what the charging system is capable of producing at cruising speed, not at idle or when trolling around town, so take that into account. Next, you’ll have to figure out how many watts it takes to run the bike. This means adding up all the electrical loads that are placed on the bike when it’s operating. Most manuals don’t list this, so you’ll have to figure it out on your own by adding up each electrical component’s draw. That can get tedious so we’ve supplied a little cheat sheet for you as a side bar.

Once you know how much electrical power is required to run the bike, you can subtract that from the alternator’s output. Whatever’s left is what you have to power up your new lights.

For example, the 2001 Kawasaki Vulcan 1500 FI’s charging system churns out 588 watts. It needs 340 of those to get itself down the road, leaving 248 to power accessories. Most conventional spotlights draw between 55 and 100 watts, although some can go as high as 130. If you pick two 100-watt units, you’re perilously close to overextending your charging system, especially if you do a lot of slow-speed riding with the lights on. By that same token, constantly forcing your charging system to operate at or near its maximum capacity creates a lot of heat, which has an adverse effect on things like rectifiers, regulators and stators, so in this case a better choice might be a pair of 55 watt bulbs; combined they’ll use 110 watts of current, which leaves you with 138 watts in reserve. That’s more than enough, so long as you’re not towing along any beer coolers and a wet bar.

The Get-Your-Hands-Dirty Part

Finding a location for your lights is the first hurdle. To get the most out of them, they should be mounted as high and as far forward as possible. Height allows light to work to its best advantage, and a forward mount prevents distracting reflections. Ideally, they should be mounted at eye level, about where your ears are. For most of us that’s an impractical location, so you’ll have to compromise. In some cases an OEM or aftermarket light bar may be available; if it isn’t, there are a variety of aftermarket clamps and mounts available that’ll let you hang the lights just about anywhere you want, from the fork tube to the handlebar. The overriding consideration here is that the lights need to have a solid and secure mount.

While the vast majority of aftermarket light kits are supplied with everything you’ll need—for instance, our PIAA 1100 LED lights came with a wiring harness, relay and switch, which essentially makes them a plug and play installation that only required one splice into the factory harness—the same can’t be said of every light kit. Fortunately that doesn’t mean you’ll have to hack something together.

Most any place that sells aftermarket lights can also supply a universal installation kit. In fact one of the best places to find them is at PEP BOYS, the nationwide auto parts chain. They offer some kits containing everything you’ll need for less than $20, which is cheaper than buying the individual components.

Installing the wiring is as straightforward as it gets. Typically, you’ll connect the spotlight’s main power feed directly to the battery or a dedicated accessory power source, via the light relay and fuse. The control switch, which activates the lights through the relay, should be connected to your bike’s high beam circuit, at least to meet the letter of the law. Though it’s not a strict requirement, I like to pick up the control switch feed inside the headlight, usually by tapping directly into the high beam circuit or through the indicator light. Doing it that way, rather than by splicing into the harness under the tank is generally more convenient, and makes it a lot easier to troubleshoot the system if anything goes wrong.

Route the harness as neatly as possible; the key things are to avoid making any sharp bends or routing the wire over or through a sharp edge that may chafe through. If the harness has to pass through any drilled holes, chamfer the edges and use a grommet to protect the wire, and don’t forget to leave a bit of slack in the harness. A harness stretched tight is one that’s waiting to break. Do yourself a favor and resist the urge to ty-wrap or permanently secure anything until you’re certain the lights work properly and the wiring is properly routed.


Driving lights can suck your battery dry in short order, and they get hot, even the LED versions. You don't want to leave them on any longer than necessary when the engine's off and the bike isn't moving.


Make the final connections to the lights and test the operation. You don’t have to go crazy here; run them through their paces and quit. Driving lights can suck your battery dry in short order, and they get hot, even the LED versions. You don’t want to leave them on any longer than necessary when the engine’s off and the bike isn’t moving. Assuming everything works, you can tidy up all the loose ends and aim the spotlights.

Instructions vary, but to aim your new driving lights, this method works as well as any. Find a level spot—a garage floor or level driveway is perfect—and position the bike 25 feet from the nearest wall. Measure the distance from the floor to the center of the spot light. Transfer that measurement to the wall, then make another mark 1.5 inches below that. The center of the spotlight beam should be adjusted to hit the lower mark, when the rider is sitting on the bike.

The usual blather

All told, this upgrade should take no more than a couple of hours, depending on how much of the bike you strip to install the wiring harness. In this instance I had to remove the fuel tank, which is a bit of a hassle, and it still took less than four hours from start to finish. As far as tools go, figure on the most basic of hand tools, and an electrical test light to help identify the high beam circuit. CR

Common Operating Loads

Although your manual should list these, it probably doesn’t. However, the nice people at Powerlet were good enough to gather them up for you. Here’s where all those electrons go.

High Beam 65 watts
Low Beam 55 watts
Number Plate 5 watts
Brake/Tail 21 watts
Instrument Panel 2 watts
Computer 25 watts
Fuel Pump 60 watts
Cooling Fan 60 watts
Electronic Ignition 50 watts

A common operating load for a standard fuel-injected bike is about 285 watts.
A common operating load for a standard carbureted bike is about 195 watts.

Courtesy Powerlet Products


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Shop Talk | Driving Light Install - Motorcycle Cruiser Magazine
Shop Talk | Driving Light Install - Motorcycle Cruiser Magazine
Shop Talk | Driving Light Install - Motorcycle Cruiser Magazine
Shop Talk | Driving Light Install - Motorcycle Cruiser Magazine