Dual-Sporting an Off-Road Motorcycle: Dual-Sporting an Off-Road Bike

There's a lot of talk these days about making an off-road bike, such as a Yamaha WR426 or a Honda XR400, into a street legal machine. There are many ways to do this. One way is to buy a ready-made kit. I've gone this route and have been unhappy with the cost, quality and durability of the components. Another way is to do it yourself. That's what this page is all about.

First things first. Nothing you do here is going to change the emissions of the bike to make it meet EPA emissions requirements. If you have a bike built by a large manufacturer, then in order for them to sell the bikes for on-road purposes, they must meet certain emissions standards. If you are reading this, then your bike probably doesn't meet the standards. But these requirements only apply to manufacturers. The EPA doesn't regulate the end user in this regard.

Which leads us to the next topic: state requirements. No matter what the EPA says, in order to get a license plate for your off-road bike, your state has to sell you one. Different states have different requirements. You may or may not be able to get a tag for your bike in your state no matter how street-legal the lights are. But don't give up hope. If you are creative and persistent, there may be a way to do it. Some states restrict these bikes by VIN. These are the hardest states to get a tag in. Some states just want your money and don't care what the bike looked like before you put lights on it. Talk to people in your local area for advice in getting a tag in your state.

The Details

We've talked about the legal stuff and now you just want to make your bike have lights so you can get a license plate so you can connect trails without having to worry about getting fined. This page assumes that your bike at least has a lighting coil already on the bike and possibly a head and tail light. If you have an MX bike, you are going to have to spend some money and get your stator rewound or get a new stator with a lighting coil. I am also assuming that you have the ability to solder and use heat shrink. Don't twist and tape these connections.

Let's start with a shopping list:

18 ga wire (red)
18 ga wire (yellow)
18 ga wire (black)
18 ga wire (blue)
18 ga wire (green)
18 ga wire (brown)
12 volt sealed-lead acid battery, 1.3 amp-hour capacity. Looks like this:

Blue LED (High Beam indicator)
White LED (Tag Light)
Solder
Heat shrink in various sizes
2- 330 ohm resistors (for LEDs)
35 amp 200-volt rectifier
Heat sink for rectifier
4 turn signals
2 3-way switches (one for the high/lo beam and one for the turn signals)
2 brake light switches. The rear brake switch can be either a pressure switch that replaces the banjo bolt or a pull switch that mounts to the frame. The front brake switch should be a pressure switch.
12 volt 2-prong automotive turn signal flasher unit
12 volt motorcycle horn
Extra kill switch (will become horn switch)

Now you've got everything you need to make a basic kit. If you want to go one step further and make the system really look good, you need a real handlebar switch set. I got a switch set off of an '04 GSX-R 600 off of eBay and it really works nicely. It replaces the three way switches, the extra kill switch and even the main switch (which I am also assuming the bike has if it has a lighting system already on it.) These switches can be found new on the internet. Just don't get one of these:

They suck.

Here's a picture of my switch set:

In order to meet most state requirements and to power all of your accessories, you will also want to put a battery in the bike for the lighting circuit. This will necessitate rectifying the current. This will also make your headlights brighter and not dependent on engine rpm to keep it bright. We'll get into all that below.

Wiring Diagrams

The first thing you need to know is how you are going to connect everything. I have put together 3 different wiring diagrams. The first one is a basic diagram that will do everything you need. You can turn the lights on and off with or without the motor running. The second is an advanced system that will automatically shut off the lights when the motor stops running. This is helpful if you don't want to leave the lights on and kill the battery when you shut the bike off but leave the lights running. The third is an override that allows you to turn the lights on when the motor is off (like the basic diagram) with an auxiliary switch. I use this for lighting system troubleshooting and if I need the lights on if the motor is off. Other wise I keep that switch in the off position.
Here are the links to the three wiring diagrams in pdf format. Read below for more detail on how to use them.
Basic Wiring Diagram
Wiring Diagram with Auto-Shutoff Option
Wiring Diagram With Auto-Shutoff and Bypass Switch

Let's Start With the Generator
The generator makes electricity for your bike to make a spark and to power the lights. These are separate circuits and they are both alternating current. The bike is wired to use the frame as a ground (common) and the two separate circuits go to various places through the stock wring harness. We will not mess with the spark circuit. But we will mess with the lighting circuit.

Voltage Regulators
To keep from blowing lights and killing your battery and other components, you will need a voltage regulator (VR). If you have a bike that comes stock with lights, it already has one. This is how it works: AC voltage comes from the generator and varies depending on engine rpm. The VR is wired in parallel with the power and is grounded to the frame. As the voltage exceeds the desired value, the VR "bleeds off" extra voltage to the frame ground and gets hot. (Touch your VR during a ride and see for yourself. Careful!) This is why VRs usually have some kind of heat sink built in or are out in the air flow- to cool them.
There will be 2 wires coming out of the VR. One comes from the generator and the other send current on its merry way to the lights. The VR is bolted to the frame and grounds itself that way so it can bleed off the undesirable high voltage.

I think this is why so many aftermarket VRs die so young. They don't ground to the frame and have no heat dissipation capability. I killed 2 in a short time from this issue. Stick with the stock VR if you can.

The Rectification of the Voldrani
Ok, I know that's a nerdy reference to Ghostbusters but now we are going to think about the rectifier. If you want a battery, LEDs, a regular horn and to have your lights on without the motor running, you will need a battery. One problem: batteries make direct current (DC). Your bike makes AC. How do we rectify the situation? (Pun intended.) With a rectifier. Go to this link to read more about it from people who know way more about the subject than I ever will.

A rectifier is an electronic device that converts AC to DC. It uses a bunch of diodes (little electronic "gates" that allow current to flow in only one direction) in a cleverly arranged configuration to do this. You can get them at Radio Shack but you can also get them from Skycraft. They are cheap and small and can handle up to 35 amps and up to 200 volts.
Here's a picture of one. They're about an inch long on each side.

You will have one wire coming from the VR, which is AC. Connect this to one of the AC terminals on the rectifier. Now find a good place to connect a ground wire to the frame. The place where the VR is connected to the frame would be a good spot. Take that wire and connect it to the other AC terminal on the rectifier. The rectifier will have (+) and (-) terminals. These are the DC current positive and negative terminals which will provide power for all the lights and accessories on the bike and will be connected to the battery.
A note about the rectifier capacity: Your bike makes at the most 15 amps of current unless the stator has been rewound. So why do we need a 35 amp rectifier? Better to have the capacity and not need it than to need the capacity and not have it. The larger the capacity, the cooler they will operate. I use a heat sink on my rectifier just to be safe.

The Battery
Now that you have regulated DC current to play with, all you need now is a battery. I don't know why everyone is so keen on "battery eliminators" and NiCad batteries. The battery I show above is small and inexpensive (less that $20) and is a real sealed lead-acid battery. They can charge and discharge just like a car battery. NiCads don't handle these repeated cyclings very well, in my opinion. And how much juice can you get out of a battery eliminator. Go with a real automotive type battery.

The two wires coming from the rectifier connect directly to the battery- (+) to (+) and (-) to (-). Then run another wire from the battery terminals to the lights. The lights will run off the battery and the generator will charge it as it drains. Use red wires for (+) and black wires for (-).

Here's the battery, rectifier, and relay switch in the air box. The black wires are the AC power and the two red wires are DC (+) and (-). The green wires are for the rectifier switch cutoff.

Taking Stock
Let's take stock of what we have done (and spent) so far:

Connected the voltage-regulated current to the rectifier
Connected the rectified current to the battery.

How much have we spent:

Rectifer- $3.50
Battery- $20.00
Wires and solder- maybe $1

If this would have been a dual-sport kit, it would be $100 so far, at least. See, you're saving money and you know how it works!

Wiring Harness From Scratch
Now that we have power, we must distribute it around the bike. Here's where the shopping list and the wiring diagram comes in. We need to get power from the battery to the front and rear of the bike and to a central switch unit. I installed my battery, relay switch, and rectifier in the air box. They fit nicely in there, they are protected from damage, and are in a central location that is easily accessible.
One way to do it is to run wires everywhere and hope for the best. A better way to do it is to make a wiring harness. You see the first items on the shopping list is a bunch of 18 gauge wires in a bunch of different colors. Here's how they will be used in the main wiring harness:

2 red wires coming off the hot (+) side which will go to the main switch and back.
1 Black for the ground.
1 Blue wire coming from the front brake switch
1 Green wire for the left turn signal
1 Brown for the right turn signal
If you plan to power a GPS or some other accessory, you'll need one more wire in the harness for that
If you want to install the auxiliary lighting switch to bypass the relay, you will need a wire for that.

You can bundle all these up and wrap them in a spiral or split loom wire wrap, or you can tape them up (not recommended) or, you can get wire already bundled with a heavy-duty outside insulator to protect against abrasion. Skycraft sells all sorts of bundled wires. You might have to call them because I don't think they sell 6, 7 or 8 conductor wire online. However you decide to do it, you need about 4 ft of wire to go from the battery to the handlebars and have enough left over to work with.

7-Conductor Wire

You will use the other colors of wires and additional single strands of wires to make the connections to the individual components. Whatever you do, make sure everything is soldered and heat-shrinked for insulation and durability. I have learned this from experience. Click here for more on making wiring harness connections.
Route the wiring harness under the backbone of the frame, over the carb and up into the air box. (I have mine routed in between the upper engine mounting brackets.) The front of the harness can be routed under the VR and will come out behind the headlight shroud.

Front wiring harness

Rear wire routing

Rear wiring harness

Neatly tuck in all wires

Whichever way you decide to go, it shouldn't cost you more than $10 for all the wires. Of course, you may decide to buy more wires than you need to have as extras. I bought 80 feet of good 18 gauge wire at Skycraft for $4. The total length of wire you will use will not exceed 50 feet.

Compare this with the cost of my dual sport kit. The kit cost $400 in 2001. All I have left from the original kit is a wiring harness and 2 turn signals. Everything else has broke or died and not from crashing or abuse. That's one expensive wiring harness!

Tag Light (that's a BRIGHT white LED from Radio Shack):