Motorcycle Lighting and Electrical Guide

By Glenn Zetterquist (Zee331)


Motorcycle Lighting and Electrical Buying Guide

Motorcycle lighting and electrical might possibly be the most feared area of aftermarket customization, rivaled only by handlebar swaps, carburetor jetting and fuel management. With this Lighting and Electrical Buying Guide, we hope to put some of your fears to rest thus opening the door to you for future electrical DIY accessory installations such as headlights, turn signals, lightbars, horns, tail lights, etc...

On the surface, motorcycle electrical systems and components can look complicated. As with many things in this life, if we examine the individual components one at a time, it’s not really that scary at all. Let’s begin by looking at the items which make up a “motorcycle electrical system.” Keep in mind that the components may vary from model to model and the best reference is your motorcycles owner’s manual.

Basic Motorcycle Electrical System Components

Basic Motorcycle Diagram

Charging System

Battery: Batteries are the center of your motorcycle’s electrical system. Put simply, the battery stores 12 volt power and delivers this power to any component which requests the power through a switch or circuit. Without a battery, the starter would not turn, which would not allow the motor to fire and therefore the system would not charge or operate correctly.

Stator: The stator on a motorcycle is similar to an alternator or generator in a car or truck. Once the motor starts, the stator generates power and sends this power (which varies depending on RPM) to the regulator rectifier and then back to the battery for recharge and storage.

Regulator / Rectifier: The voltage regulator takes the raw power from the stator, collects it and makes sure the system maintains a consistent voltage to prevent the system from being overloaded.

Electrical Wiring

Battery: As mentioned earlier, the battery is the master of the electrical system. It provides 12 volts of power to every accessory which asks for power.

Fuse / Fuse Block: A fuse (or a fuse block) sits between the battery and the positive lead of any electrical accessory. Fuses prevent power surges from “shorting out” or destroying parts of the electrical system. All factory accessories route to a fuse block and most aftermarket accessories come with an in-line fuse.  

Wiring Harness: The “wire harness” is a group of individual wires wrapped together to form one thick bundle which is routed from the battery / fuse block to various areas of the motorcycle.

Headlight, Tail Light, Turn Signals: These are commonly two or three wire leads off of the wire harness which get power from the battery / fuse block when instructed to do so from the corresponding switch.

Motorcycle Wiring 101.1 Turn Signals (front and rear)

 Hundreds of wire colors have been used for motorcycle wire harnesses over the years and across the brands. Typically, every color designates a different and specific function. Initially this can be very confusing, but when broken down there are really two types of wires: power and ground. Every manufacturer as well as make / model has its own unique color code system.

Two Wire Turn Signal Example Green = Ground
Orange = Left Turn Signal
Light Blue = Right Turn Signal

Three Wire Run & Turn Example Green = Ground
Orange w/ White = Left Running Light
Orange = Left Turn Signal
Blue w/ White = Right Running Light
Blue = Right Turn Signal

Turn Signal Accessory Installation:

Turn signal accessories will come with either two leads or three just like factory harnesses. A two lead light can be used as a running light or a turn signal (not both) unless you install a “Run Turn Brake Controller.”  

Why? One wire connects to a ground wire and the other wire will connect to either a running light wire or a turn signal wire. Wiring a two wire (single circuit) accessory to a two wire system is just as simple as wiring a three wire accessory to a three wire system with one wire to ground, one to run and the last to the turn signals. Now for two very common questions

1: How do you wire a three wire accessory to a two wire harness?
2: How do you wire a two wire accessory to a three wire harness?

Two Wire Set-Up          BM-JY127-LED-BLK Three Wire Set-Up           KY-1431

Answer 1: The three wire accessory can be wired up to the two wire harness but you will have to cap off the third wire from the accessory.

Answer 2. Is the accessory intended to be used as a running light or a turn signal? Test the accessory (light) and find the wire with the brightest light. If used for a turn signal, this wire will attach to the motorcycle turn signal wire and the second wire connects to ground. If used as a running light, you will attach the non-ground wire from the accessory to the power wire.

IMPORTANT: If you are upgrading your turn signals from incandescent to LED bulbs you will need to install a load equalizer or your turn signals will blink 2x faster than normal!

You know the blink that manifests itself when a bulb is burned out? Why is this?

LED bulbs draw much less power than incandescent bulbs and the system thinks the bulb is defective (or burned out) and it sends the warning signal as a fast flash. This can be rectified with the addition of a load equalizer. While very similar, not all load equalizers are created equal. There are 2 amp, 4 amp, self-regulating, model specific, and alarm safe load equalizers, so make sure you get the one which is best for your application.  

Load Equalizer Installation: Most load equalizers will have three wires. One will connect to ground and the other two will connect to left and right turn signal wires.  

Motorcycle Wiring 101.2 Headlights

Effective headlights might possibly be one of the most important accessories on your motorcycle as they allow you to see and be seen. Headlight upgrades are very simple and in many cases they can even be cost effective. Most motorcycle headlights bulbs are either H4, H7 or H9.  They can be identified by the writing on the bulb as well clues at the connector. H4 bulbs have three posts, H7 bulbs have two posts, and H9 bulbs have housings shown below.

Pia H4 Bulb PIAA POwer Sports H7 Putco Halogen H9 Bulb

In most cases, stock (or standard) bulbs are rather weak in power but high in wattage, which can put a drain on the electrical system of your motorcycle. These simple bulbs can be upgraded to hi-output bulbs which generate more light output using lower wattages. Upgrades such as this can be done through the bulbs themselves (such as the images above) or the bulb can be replaced with an HID or LED system.

When it comes to LED headlight and driving light replacements, Kuryakyn leads the way with their Phase 7 series of lights. Pictured here is the 7” LED headlight and 4.5” LED Passing Lamps. See the You Tube installation here: Phase 7 Installation

HID kits come complete with a HID bulb, wire harness and ballast that produce 3x greater light than halogen and 10x greater light than a regular bulb. Watch Video

Another cost effective way to “enhance your oncoming visibility” is the addition of a PathBlazer from Kissan. This simply plugs in between your stock bulb or upgraded bulb and modulates the high beam from 100% ON to about 17% OFF multiple times a second. Watch the PathBlazer video.  

Motorcycle Wiring 101.3 Driving Lights

Headlight upgrades are great, but if you are looking to cast the most light possible, a driving light set is a must. Historically, motorcycle driving lights have been limited to traditional 4” spots referred to as a “lightbar.”

While lightbars are effective, they are not the perfect look for every type of motorcycle. In the spirit of customization, we now have driving lights which mount to forks, highway bars, floorboards, and just about anywhere imaginable. Driving light kits come in halogen, HID, and LED options.
When researching driving lights, be sure to verify if the kit comes with wire harnesses for a clean and simple installation. Most wire harnesses come complete with an on/off switch, relay, fuse, and a wire loom ample for the job. Our favorite aftermarket driving light harness is from Kuryakyn part number KY-2202.

Why is a harness important?

Many driving lightbars have no harness and are expected to be wired to the headlight High or Lo beam. The problem there is twofold:

1: There is potential to short out or overload the stock headlight circuit as the load is being at least doubled.

2. A standalone harness will allow you to run the driving lights
in the daytime, nighttime, with high beams or low beams. A wire harness puts you in control.

Motorcycle Wiring 101.4 Taillights

Motorcycles get rear ended on a regular basis and it can only make sense that a portion of these accidents are caused by the lack of light our bikes emit from the rear. Most motorcycles have a single small bulb assigned the task of making you visible and telling others you are braking and slowing down.

Today there are many modern options to help light-up the tail section of your motorcycle making you more visible to the traffic to the rear. A few of our favorite options are as follows:

1. Run Turn Brake Controllers are fantastic devices that turn a single filament or single circuit turn signals on the rear of the bike function as running lights, turn signals and brake lights. This is quite possibly the quickest and easiest way to “light up the rear” of your bike.
*NOTE: If your stock turns are amber, you will need to swap the lenses for red.

2. LED Bulb Replacements come in many forms and are simply a replacement for your dim OEM bulb.

3. Tail Light Housing & Light Replacements are the best way to customize your bike while increasing your visibility at the same time.  The Tombstone Tail Lamp has been a staple accessory in the motorcycle world for generations. Today Kuryakyn has stepped up the game with an LED Tombstone for Harley Davidson as well as Tombstone for Metric applications which allow the addition of modern turn signals.

Conclusion: The lighting of your motorcycle could the most important and often used lifesaving accessories of your motorcycle. Being able to see and being able to be seen are crucial elements of our motorcycling lifestyle. Choose your accessories wisely and choose the accessories which will best enhance and illuminate your ride.

We hope this electrical and lighting buying guide has shed some light on this very important and often scary topic. Until next time, take care and ride safe.

Kyle and the Cruiser Customizing Team