Joe Tessitore is a strange guy. Most bike builders hate working with motorcycle wiring, but not Joe. It’s his favorite part of the build, and the source of most of his business. So we’ve asked Joe to demystify the motorcycle electrical system, and provide an easy tutorial guide to sparking your bike back into life.
The most overlooked, forgotten, or avoided aspect of building a custom motorcycle has to be the electrical system.
You can spend lots of time and money building a high performance engine or sculpting beautiful lines. But if there’s no spark, you just built a really nice paperweight.
That’s where the motorcycle wiring harness comes in. There are many different ways to wire your bike, but for this tutorial we’re going to assume that your factory harness is like the ones I usually find: cut, spliced, taped, cracked, and abused by countless previous owners.
We’re going to trash that one and start from scratch with a bare-bones basic harness—one that’s just enough to get you on the road, and should work for most vintage bikes.
Let’s start with the must-haves for your bike wiring:
A new modern regulator/rectifier. This takes the AC current produced by the stator and changes it to DC current to charge the battery. It will also keep the voltage from getting too high and frying your system.
Most often you can find it under the seat area or under one of the side covers. It’s a critical part of your charging system—and the easiest part to upgrade. The old ones worked poorly to begin with, and chances are, the stock one is dead or on its way out. Get a quality one from a company like Rick’s Motorsport Electrics.
Replacing points with electronic ignitions. These send the signal to the coils telling them when to fire the spark plugs. While a traditional points ignition works fine when adjusted properly, it does require periodic maintenance and the know-how to get it dialed in just right.
For this reason many riders choose to upgrade to an electronic unit that is mostly maintenance free once installed. The most common of these are the Pamco and Dyna (below) units. They’re relatively affordable and produce great results. They also eliminate the old condensers, which often fail.
For those with larger budgets or dreams of racing there are higher end optical ignitions like Power Arc which give the most precisely timed spark for optimal power.
A brand new battery. Most street bikes won’t run without one and if the charging system was week or the bike sat for a long time, don’t take the chance. Just replace it.
Quality wire and connectors. I recommend at least 16-gauge thin stranded copper primary wire. Never use solid core made for home wiring (I’ve seen it done). Speaking of blank, nothing says “I built my bike at Home Depot and Pep Boys” like those red and blue crimp connectors. They may do the job, but if you want a professional look, go with proper supplies from Vintage Connections (below). They’ll look the part and match up to existing connectors already on your bike.
Optional goodies for the ambitious.
These aren’t completely necessary but any time you can eliminate a possible failure point in your electrical system, you’ll be ahead of the game.
New ignition coils. These produce the power to fire the spark plugs. They’re usually found under the gas tank. Most running motorcycles still have perfectly good coils that will function well with newer electronic ignitions.
However, if your plug wires are damaged or you suspect a failure, it’s always a good idea to replace them with something new. While companies like Dyna make very good coils, I’ve had plenty of success with less expensive options like Emgo. Don’t expect aftermarket coils to match up to you stock mounts. You may have to fabricate a bracket or two but they’ll still work just fine.
Upgraded stator. The stator produces the power to run your electrical system and keep your battery charged. It’s usually under the left side cover of the engine at the end of the crankshaft. Most older machines had weak charging systems to begin with, and time has only made them worse.
If you find that upgrading the regulator/rectifier still hasn’t given you enough power, it may be time to look into this. It may not be available for all bikes but some of the more common ones like CB350s and XS650s can take advantage of offerings from Rick’s or Hugh’s Handbuilt. These units will put out a lot more charging power and in some kickstart only cases, allow you to run without a battery.
Motogadget accessories. Ah, the pièce de résistance or gold standard for motorcycle wiring. When you’ve spared no expense on your build and want a professional looking installation, Motogadget parts are the ones you reach for.
The m-Unit is a self contained, programmable, and well-labeled electrical heart for the wiring system. It uses electronic circuit breakers, making fuses obsolete. Just hook it up to your battery then run wires out to every electrical component on the bike. Headlight, taillight, turn signals, horn, the lot. There’s even an integrated alarm feature.
Definitely plug and play for someone with a little patience and a free weekend. Motogadget also offers options for electronic flashers, digital gauges, and my personal favorite, RFID keyless ignition.
Now that you have the essentials, let’s get down to business.
It’s best to think of motorcycle wiring like a circle: Power leaves the battery from one terminal, passes through whatever will use that power (lights, horn, coil, whatever), and ends up back to the opposite terminal of the battery.
If that circle is ever broken, something won’t work. Here’s the basic step-by-step:
1. Connect the negative (-) terminal of the battery to a clean, bare metal part of the frame. Preferably this would be an engine mounting point. This makes the entire frame a grounding point so every light or accessory can be grounded anywhere on the frame to complete the circle of our electric circuit. On a kickstart only bike, this can be the same size as the other wires (14-16 gauge). If using electric start, it must be much thicker (4-6 gauge).
2. Connect the positive (+) terminal to an inline fuse holder. I prefer the newer blade style over the old glass tubes, and use between 20- to 30-amp fuses.
3. From the fuse holder, we’re running a wire to your ignition switch. It can be a keyed switch or just a toggle if you’re going to hide it somewhere discreet. Either way I recommend something that will handle at least 30 amps as all power to your electrical system is running through it.
4. Now that we have a way turn the power on and off, I like to run one power wire from the front of the bike to back. I call it the backbone. Every powered accessory will tap into this wire. In this case, start with the remaining wire from ignition switch and attach it to the backbone wire.
5. Attach the hot wire from the headlight to the backbone wire and ground the other wire to the frame. Do the same with the taillight.
6. Your front and rear brake light switches each have two wires. Attach one wire to the backbone wire and the other one to the third wire on your taillight (brake light wire).
7. Your coils should have two small input wires (in most cases). Attach one from each (if you have more than one coil) to the backbone wire. The remaining wire connects to your points or chosen electronic ignition. The thick wire with the cap goes to the spark plug—but you already know that, right?
8. If you’re using electric start, connect one of the lugs of your starter solenoid to the positive (+) battery terminal with a 4-6 gauge wire. The other lug connects to the thick wire going to the starter. You also have two small wires or connector tabs on the solenoid. Connect one of these to the backbone wire and the other to your starter switch. Ground the other side of your starter switch to the frame if not already grounded through the handlebars.
9. Now for the charging system. Your new regulator/rectifier should have 3 yellow input wires. Connect these to the wires coming out of the stator (usually from the left side of the engine and the order doesn’t matter). Connect the Red wire from the reg/rec to the positive (+) battery terminal and the green wire to the negative (-) terminal.
Some bikes, like CB750s, will have an additional white field coil wire bundled with the yellow stator wires. On bikes like this, the reg/rec will have additional wires that connect to the field coil wire and powered backbone wire. Be sure to check the instructions that came with your unit.
10. That’s it! Turn the key, hit the starter button, and enjoy the sweet sound of success. You just rewired your bike!
Since this is just a basic system to get the bike running, I’ve left out things like turn signals, horn, and indicator lights. If you’d like to install these as well, just follow the same formula, power from the backbone wire, through your switch, and out to your light or accessory.
Lastly, you can wrap up your wiring masterpiece however you see fit. I like heatshrink tubing, but many people prefer to wrap using electrical tape or plastic wire looms.
Just remember to keep the wires secure and away from any sharp edges or heat sources. Broken or melted wires are the most common source of electrical failure I see.
Connect the Red wire from the reg/rec to the positive (+) battery terminal and the green wire to the negative (-) terminal. Some bikes, like CB750s, will have an additional white field coil wire bundled with the yellow stator wires.How do you read motorcycle wires? ›
- Connectors: Disconnect points for wires.
- Ground: Connection to motorcycle frame.
- Bulbs: Generic "load" (power-consuming component).
- Switch: Opens or closes circuit.
- Diode: Prevents current opposite direction of arrow.
- Fuse: Opens circuit in case of excessive current.
When installing your new battery, simply slide the new battery into place and attach the cables to the terminals. This time, attach the positive side first and the negative side second.What are the 3 wires going to alternator? ›
There are three key wires in the loop: a positive wire for the battery, a sensing wire for voltage, and an igniting wire. The ignition input wire is linked to the engine. The energy detection cable monitors voltage and transmits it to the converter, while the energy wire links the alternator and the engine.Is a motorcycle AC or DC current? ›
Additionally, motorcycles need DC, or direct current, to power the electrical systems. Motorcycle alternators produce AC, or alternating current, requiring the rectifier/regulator to complete the system.Does a motorcycle charge its own battery? ›
The relationship between your motorcycle battery and engine functions much in the same way as a car battery. The alternator is fitted with a regulator that charges the battery while you ride.What are the 3 motorcycle types? ›
The six main types of motorcycles are generally recognized as standard, cruiser, touring, sports, off-road, and dual-purpose.Do I attach the negative or the positive first? ›
“Positive first, then negative. When disconnecting the cables from the old battery, disconnect the negative first, then the positive. Connect the new battery in the reverse order, positive then negative.”How do I identify positive and negative wires? ›
- The positive current must be red.
- The negative current must be black.
- The ground wire, if present, must be white or grey.
The positive wire, also commonly called the hot wire, will typically be black in color. It is the source of the electricity. The electrical current travels from the outlet or other power source on the positive wire, so if it is plugged in anywhere, it should be considered a live (and dangerous) wire.
- Phase 1 - Black.
- Phase 2 - Red.
- Phase 3 - Blue.
- Neutral - White.
- Ground - Green, Green with Yellow Stripe, or Bare Wire.
A: N is neutral ( white wire) L is line or the hot side (black wire).Why is neutral between 1st and 2nd on a motorcycle? ›
As stated in other responses, neutral is in the position between 1st and 2nd gear as a form of logic and safety. In a sequential transmission the sensibility of placing neutral between 3rd and 4th gears creates user difficulty in getting to desired gears after stopping.What happens if you connect the negative terminal first? ›
Never connect the black cable to the negative (–) terminal on your dead battery. This is very dangerous, could result in a possible explosion. Make sure you follow the instructions in your owner's manual when jumpstarting your vehicle.What happens if you disconnect the positive terminal first? ›
It's important to disconnect the negative side of the battery first, otherwise you can cause an electrical short if the positive is removed first.Do you hook up red or black first? ›
Attach the red jumper cables first. Start by clamping one red cable to the positive side of the battery that won't start. Then attach the other red clamp to the positive side of the working battery. Next, clamp one black cable to the negative side of the working battery.What sends the signal to an alternator? ›
These systems are controlled by the vehicle Engine Control Unit (ECU). As the vehicle demands more load the ECU sends a signal to the alternator requesting it to start charging.What sends power to the alternator? ›
Each of these vehicle components has multiple parts at play—all working together to power your vehicle: Your battery powers the starter. The starter kickstarts your alternator.What voltage should a motorcycle charge at? ›
If your voltage is at or above 12.4V — you're good. If your voltage is below 12.4V after a charge — you need a new battery.How many volts should a motorcycle stator put out? ›
It should read anything above 12.0v but under 13.2v but ideally between 12.5 – 12.9 DC volts is required. Any less than this, you may start to encounter starting problems as the Battery will not have enough juice to turn the big twin motor over.
Motorcycle batteries can be jump started from another motorcycle, car battery, or portable battery jump starter. Most motorists keep jumper cables in their car, so it shouldn't be too hard to find someone who is willing to help you out.What amp should I charge my motorcycle battery at? ›
When charging a motorcycle or other small battery, the battery charger should not exceed 3 amps. Most automotive types of battery chargers are not suitable due to higher current output.Can I use car battery to start motorcycle? ›
A large car battery has plenty of energy to fire up a bike within a few seconds, without the need for the engine to be running.What is a code 3 motorcycle? ›
In the old days, we used to call them Code 3 motorcycles. The system worked like this – on the motorcycle's papers, there were three codes: Code 1 meant the bike was new, Code 2 meant the bike was second hand and Code 3 indicated that this motorcycle was in an accident and insurance has written it off.What motorcycle type is best for beginners? ›
A street or a roadster motorcycle can make for a great beginner bike because they are typically easy to handle. Additionally, the seating position is comfortable. These bikes are quick to master, and they can be that perfect generic bike type to get you going.What's the easiest motorcycle to ride? ›
- Harley Davidson Sportster. ...
- Kawasaki Ninja 650. ...
- Triumph Bonneville T100. ...
- Ducati Monster 797. ...
- Suzuki SV650. ...
- Yamaha MT-07. ...
- KTM 390 Duke. ...
- Triumph Street Twin.
When connecting a car's battery cables to the terminals, ensure to put the positive first before the negative cable. This is because the positive cable will not arc if your wrench or spanner touches the car's body in the process of tightening up the cable due to the absence of the ground (negative cable).What happens if you connect positive and negative wrong? ›
The cable on the positive terminal uses +12V while the one on the negative side uses -12V. If the positives and negatives are switched, the battery will try to compensate and make the negative 12 volts into a positive charge resulting in a huge surge of power and an enormous amount of heat to be produced.Which terminal do you jump first on? ›
Start by connecting the positive (often red) clamps of the jumper cables to the positive terminals of your battery. These are often marked, but they can be hard to see. Be sure to look closely to ensure that you are connecting to the right portion of the battery.How do I know which wire is which line? ›
Line Wire - Generally connected to the bottom half of your switch. In some cases, line wires are marked with “line”, “pwr”, or a lightning bolt symbol. Also, on some traditional switches, the line wire is connected with a black or silver screw that is a different color than any other screws on the switch.
The protective ground is green or green with yellow stripe. The neutral is white, the hot (live or active) single phase wires are black , and red in the case of a second active.Can you use a black cable for positive? ›
The red one is positive (+), the black one is negative (-). Never connect the red cable to the negative battery terminal or a vehicle with a dead battery.Should the neutral wire be live? ›
Neutral is not necessarily zero and assuming it is will likely get you electrocuted. The general idea is that live supplies the voltage and neutral is the return wire. In most installations the live is at the required voltage and the neutral line is connected to ground at some point (so zero volts relative to ground).What are the three 3 types of wires and their respective color represents? ›
Hot wires: Black, red, orange. Neutral wires: White, brown. Ground wires: Green, yellow-green.What are the 4 types of wire? ›
- Fuse Wire. ...
- Magnet Wire. ...
- Stranded. ...
- Litz Wire. ...
- Tinsel Wire. ...
- Braided. ...
- Wire Harness.
No, the neutral and ground should never be wired together. This is wrong, and potentially dangerous. When you plug in something in the outlet, the neutral will be live, as it closes the circuit. If the ground is wired to the neutral, the ground of the applicance will also be live.What does L1 L2 L3 mean in electrical? ›
L1, L2, and L3 coils are live wires with each on their own phase carrying their own phase voltage and phase current. Two phases joining together form one line carrying a common line voltage and line current. L1 and L2 phase voltages create the L1/L2 line voltage. L2 and L3 phase voltages create the L2/L3 line voltage.How do you tell which wire is hot and which is not? ›
Hot wire is identified by its black casing. This is the main color of hot wire for most homes. However, other hot wires can red, blue, or yellow, although these colors can indicate a different function besides powering an outlet.What is the N 1 rule bike? ›
While the minimum number of bikes one should own is three, the correct number is n+1, where n is the number of bikes currently owned. The idea behind n+1 is that you should own one more bike than the amount you currently own.What does 1 down 4 up mean? ›
One down four up is the shift pattern commonly used on motorcycles of the 70's, 1 N 2 3 4 5. It's usually one of the first lessons learned in riding and captures the pure thrill of riding a motorcycle from the first ride on.
The 2 second rule, as the name suggests, allows at least 2 seconds between you and the vehicle in front. The 2 seconds safety buffer should provide the rider enough time to slow down or stop in many situations. As can be seen in the diagram, the motorcycle rider following the red car has a 2 second gap.Where does the negative wire go on a motorcycle? ›
Connect the red positive terminal on the dead battery to the positive terminal on the live battery. Clamp the black negative terminal on the live battery, but make sure you place the opposite negative clamp on a grounded and unpainted metal surface of your motorcycle. Typically, the chassis is suitable for this.What needs to be safety wired on a motorcycle? ›
In motorcycle-racing competition, rules require safety wiring of various components such as axle pinch bolts, oil-pan drain plugs, oil filter covers and other caps and points of closure.How does the electrical system work on a motorcycle? ›
The alternator creates alternating currents to run the bike and charge the battery. The regulator/rectifier changes, or rectifies, the alternating current produced by the alternator into direct current so it can be stored in the battery and regulates the amount of current produced to prevent overcharging.What are the 3 wires on a motor? ›
For a standard 3-wire motor, the lead wire colors are typically white, red, and black. Black is always connected to neutral (N). Both white and black are connected to the 2 terminals of the dedicated capacitor.Do I need fuse on positive and negative? ›
It is not necessary to fuse both positive and negative leads of the supply. A single fuse will break the circuit sufficiently. Putting a fuse in the negative rail will not really be of help as it is unlikely that both fuses will blow at the same time.What is two main things you should never do on a motorcycle? ›
- Don't tie shoelaces in loops. ...
- Don't watch the speedometer, watch the road. ...
- Watch the tires of the vehicle in front of you (don't trust brake-lights blindly) ...
- Don't change speed in the middle of a corner. ...
- Change gear before an overtake, not during the overtake.
The short answer is no. You only need one—and that's the pull cable.Should feet touch ground on motorcycle? ›
Not at all. Nothing except the fact that not more of us do it. This myth scares people, and that not only produces riders that are not riding to best of their abilities, but it also keeps many potential riders from getting a bike in the first place.What voltage should a motorcycle run at? ›
Motorcycle batteries operate between about 12 and 14.5V — any more than this puts a lot of stress on them. A fried reg/rec means you might see voltages of over 20V when revving high which is bad news for the battery.
Additionally, motorcycles need DC, or direct current, to power the electrical systems. Motorcycle alternators produce AC, or alternating current, requiring the rectifier/regulator to complete the system.Which of the 3 wires is not required? ›
Live, neutral and earth mains wires
In a plug, the live wire (brown) and the neutral wire (blue) are the two wires that form the complete circuit with a household appliance. The earth wire (green and yellow) does not normally form part of the circuit and is included as a safety wire.