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THE REVIVAL APPROACH TO WIRING AN M-UNIT

"The map may not be the territory, but it sure helps a lot."

The m-Unit is light years ahead of any other power distribution module on the market, and the best thing to come to motorcycle electrical restoration ever, Hands down. Installing one is no small task; if it's your first m-Unit installation and you are not well acquainted with the OEM electrical system, you might expect to spend a minimum of 50-60 hours on this project. So we've put together a series of articles and diagrams to help streamline the process for you.

In my experience, it usually isn't that difficult to get the wires to connect from the correct things and make the system work; the difficulty comes in making it all as simple as possible while looking perfect. If you invest time, in the beginning, to familiarize yourself with your factory electrical system along with the m-Unit and then map out your installation, you'll have some familiarity with the territory before you ever set foot on land. 

 

Minimum required for the task:

1 A legible, accurate, OEM wire diagram 

2 m-Unit

3 Wire to build your new harness

4 Main fuse holder

5 Complete charging and ignition system components

6 Wire loom or tape

7 Heat shrink

8 Crimp tools, Solder, and solder iron

9 Time 

10 Patience

 

the same but different

Nearly all carbureted bikes are going to follow the same basic wiring, with a few exceptions, such as convoluted tour bikes or the era just before fuel injection was introduced. The main differences in most instances will be your OEM ignition and charging system wiring and whether you choose to use kickstand switches, kill switches, charging lights, etc. 

There are, in some cases, more than one way to go about wiring certain elements of the m-Unit and have everything still function. Whether you follow our methods or someone else's, you should try your best to make sure all positive power wires are metered by the m.Unit's circuit protection or an added fuse. 

How do you eat an elephant? One bite at a time...

The best practice is to break this down into bite-sized pieces. Print out multiple copies of your OEM diagram, and on each one, highlight a different portion of your system on each page. Start with just one part, the headlight circuit, for example, and knock that little bit out before moving on to the next. Doing it this way makes it a lot easy to wrap your head around it and easier to retrace your steps should something need debugging. 

One tip for making it easier is to use a highlighter to mark just the wires that connect to the ignition system. For the first pass, don't highlight down the branch circuits, and try to only focus on the wires are connected from "A" to "B" points; most of the wires in the ignition system will be connected this way, and you will come back to the branch circuits later. Once you have all the "A" to "B" circuits identified, you can determine what is going on with the circuits that branch and have multiple connections. On carbed bikes, it is most likely that you have a positive connection that supplies power from the ignition switch and a ground wire that ties into the chassis. On Fuel-injected bikes, it is a bit more complicated with the fuel pump relay and the sensors, but following along with this method, you should be able to isolate the system in the diagram and identify the switched power connections that need to be powered with the "AUX" output.

You can use the blank template included with our Universal m-Unit Wiring Diagram to trace out the various systems of your new wiring harness. 

It helps me to understand how the m-Unit integrates into the system by breaking the wiring up into 3 subsystems.

 

1. Charging - This consists of the wiring from your magneto or stator, Reg/Rec, and battery. The better part of this system will remain unchanged.  If you have an old system with a separate regulator and rectifier or your Reg/Rec is 20+ years old, it is time to replace it with a quality modern component. The materials in older Reg/Rec's have a shelf life and are well past the expiration date. The Reg/Rec deals on eBay/Amazon are often too good to be true, and the lack of quality control may cost you more down the road. If you are installing a Lithium battery of any kind, you need a lithium optimized Reg/Rec, which you can find on our site. 

WHAT YOU NEED TO DO. Using your OEM wiring diagram, trace the wires back from the Regulator Rectifier, determine which wire provides Rectified 12v+ power back to the battery. This wire will need to have the Main fuse between the Reg/Rec and Battery. Do not get confused by the Motogadget diagram, where the 12v+ power to the m-Unit branches from the same Reg/Rec wire to the battery. The 12v M-Unit terminal can be wired directly to the battery or spliced with the Reg/Rec to battery wire. The results of both methods are the same.

 

2. Ignition - This is your Points, Black Box, ECU, whichever you have, and your coils, etc. For most ignition systems, the only amendment to the wiring will be to route the 12v+ power wire that supplies the ignition system to the IGN OUT terminal on the m.Unit. One exception to this is if you have a CDI, Capacitive Discharge Ignition system. If you're not sure whether you have a CDI ignition, you can find instructions on how to determine what you have in our CDI X m-Unit Article. Also, just because your wire diagram says you have a CDI isn't enough to go off of.  Translations from many languages to English regularly use incorrect terminology on their diagrams. Any ignition module may be labeled as a CDI regardless if it's a TI or TCI; I'm pointing at you, Honda. 

 

WHAT YOU NEED TO DO. To wire a stock ignition system with the m-Unit, you need a clear and correct wire diagram for your bike. The basic plan is to keep the OEM system intact and simply supply power from the m-Unit "ignition" output. Start by identifying the spark plugs or coils in the diagram and trace their connections back to the ignition control module or points and then on to any devices connected to it, making a note of any connections that are powered from the ignition key switch. Follow the branches and get an understanding of what is connected to what; usually, this includes kill switches and safety switches. Any connections to the engine sensors, pulser, or trigger coils should be maintained as original, and the only changes that need to be made are connecting the power feed wires to the m-Unit "Ignition Out terminal."

 

3. Ancillary (m-Unit) - The m-Unit acts as a brain that controls voltage for everything on your bike, aside from the charging system. This subsystem also includes all of your lighting, switches, and anything else that has an assigned input or output on the m-Unit.

 A Few  Notes:

Grounds - It is of vital importance that ground connections be stripped of paint and have a clean, uncorroded, uninterrupted path to ground. Handlebar button/switch grounds should be tied together, and a single wire runs back to the m-Unit Main ground.

It is not a bad idea to run most/ all grounds back to the m-Unit main Ground location to ensure they all have ideal continuity.

 

Some things to know about turning your bike on. 

1. The mo.Unit will only recognize a two-position on/off key switch. The parking lights are activated by turning the ignition key to the off position while the Highbeam is activated. If you use a three-position switch, on/off/park, you will leave the 3rd parking position open, making sure to seal off the ends of any terminals or wires to avoid electrical shorts. 
2. The Keyless Go feature is not a replacement for an ignition switch. You will have to have some sort of latching power switch, whether it's a key or hidden toggle switch or button. You will not be able to pair with the mo.Unit without an ignition switch, and you will not be able to start your bike if for any reason you can not pair with the mo.Unit. It's a neat feature but can not be relied on 100% of the time.

Gauge & Indicator lights - The m-Unit handles power distribution and control, so it doesn't really affect much with the gauge and warning lights. Those remain basically the same as stock, with one exception, the power comes from the "AUX" output. This means the oil pressure light gets power from the m.Unit, and then the switch is the sensor on the engine, which closes the circuit when the oil pressure is too low. Basically, the neutral light and oil pressure light use a switched ground configuration, and the high beam and turn signal indicator uses a switched positive configuration. See our m-Unit wiring diagrams for a visual explanation.

 

Wired control switches - DO NOT have power flowing through them. Do not connect these to 12v power. This includes brake switches. The m-Unit is a micro-controller; it reads ground signals sent by a momentarily pressed button and turns on the associated function. This is fundamentally different from all OEM controls. You have 2 wires; one goes to ground, the other goes to the m.Unit input.

 

How the AUX 2 Fan Delay works - Choosing this option in the setup menu will program the AUX outputs to come on along with the Ignition when you switch the key to the on position or otherwise turn the bike on. When the ignition is cut off, the AUX 2 will maintain power in order to continue cooling the engine for 120 seconds after then shut itself off. 

 

DOCUMENT YOUR WORK!!!! -  I can’t stress this enough, do it every time you work on the bike. Keep notes of what you’ve done. Keep documentation for all of your components, wiring diagrams, and notes. You will not retain all of this in your memory and down the road will all be vital information for either you or the new owner. Not to mention, when you email us asking for help the first thing we're probably going to ask for is a diagram of your installation, because how else we going to remotely troubleshoot your bike when we can't even see your work?

 

A frank conversation about the m.Button:

You don't need it... All the hype around this product gives the impression that it's a magic bullet that will make this "intimidating" project so much easier for the uninitiated. Fact is, once you wrap your head around all the steps involved, it's no less tedious or difficult than merely running a small bundle of wires through your bars, keeping in mind that since there's no voltage going through the switches, that wire can be as small as you'd like. 

Not only does the m.Button not make installation more manageable, it also introduces the potential for three vexing and potentially dangerous issues that otherwise couldn't occur. 

1. m.Button Mechanical failure. They can break for no apparent reason causing one or more control functions to not respond.  
2. Phantom switch activations. Radio Frequency Interference from the ignition coils triggering switches to turn on or off on their own accord. 

 

Electronic Fuel Injected (EFI) Bikes:

 

Carbureted bikes will be much easier to tackle than a fuel-injected motorcycle and are an excellent place to start before taking this on. Rewiring a fuel injected bike is a big project, and the planning stages are vital to a successful install. Every Make and model follows different rules for power management, so a mo.Unit diagram for a BMW K1100 will not be applicable for a Ducati Monster, much less a BMW R1100. It isn't necessarily that difficult if you know what you are doing, but it takes a lot of time, patience, and homework. 

 

Beginning around 2010, another challenge you may encounter is an immobilizer. The bottom line is that you can't remove certain components in many situations without triggering the immobilizer. The most common solution is to replace the OEM ECU with an aftermarket ECU or piggyback module to remove the security feature.

 

As you near 2015 and on CANBUS protocols become more prevalent and make mo.Unit installs impossible or, in the very least, so complicated and impractical that it makes installation unfeasible. 

 

The biggest tip I can give is to pick one thing at a time and work it out, i.e., TPS sensor, get that connected, then oil temp sensor, then starter solenoid, etc. By tackling it one bit at a time, it isn't as overwhelming. If you work from the sensor back to the ECU, you can get the routing and cable lengths just right and then re-crimp with new terminals and install them back into the connector. 

If you aren't relocating electrical components, you might be able to leave the main factory loom for the ECU/EFI mostly intact and just clean up the rest of it. But if you want a clean harness, you'll want to start from scratch.

 

If the ECU has integrated safety systems for things like the side stand or clutch switch, you will need to short those circuits to ground to always be in the ready state. The mo.Unit will now be managing the power to the starter motor, and you can reintegrate the kickstand and clutch switch into the mo.Unit wiring if desired. 

 

This is the stuff you need to keep. This list is based on the simplest system possible and does not include "safety interlocks" like the clutch switch, side stand switch, etc. We often eliminate these things, but it does become the rider's responsibility to make sure the bike is in neutral, or the clutch is in before pushing the start button, and also side stand is up before riding off...its usually not that big of a deal but some people really want the built-in safeties, and that's okay too. 

 

Must Keep or replace with new:

• ECU/ECM
• Ignition coils 2x
• Starter solenoid
• Starter motor
• Pickup coils
• Alternator
• Regulator / Rectifier
• Fan Motor
• Thermo switch for fan motor

 

m-Unit Blue/Basic Universal Wiring Diagram

m-Unit V.2 Universal Wiring Diagram