motogadget m-unit into CB250N wiring loom HELP!!
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motogadget m-unit into CB250N wiring loom HELP!!

This is a discussion on motogadget m-unit into CB250N wiring loom HELP!! within the Technical FAQ's forums, part of the Caferacer FAQ's category; I need help! Welding, rebuilding engines, powdercoating, all easy, but I am no Harry Potter when it comes to the dark art of wiring!! My ...

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Thread: motogadget m-unit into CB250N wiring loom HELP!!

  1. #1
    Junior Member Segmant's Avatar
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    motogadget m-unit into CB250N wiring loom HELP!!

    I need help!

    Welding, rebuilding engines, powdercoating, all easy, but I am no Harry Potter when it comes to the dark art of wiring!!

    My loom is a working original mess, since i stripped and got rid of all old parts of my bike im left with an exposed loom which I decided to leave just to finish the bike.

    Now i have more time and the weather is shit ive decided to either:

    1. Extend the loom to hide everything under the tank, keeping the battery and fuses and flasher unit etc in the small battery box i made under my seat. (i have a tiny 4 cell Antigravity battery which is awesome) which i can easily do... probably
    2. buy the m-unit from motogadget to eliminate a lot of the earthing wires, flasher unit, 2 of the three fuses and a few other messy bits probably, just really slimming down the loom


    I really want to use the m-unit but im scared off by the old diagram of the electrics i have, i don't know where to start!

    Ive attached to old wiring diagram, the simple one that motogadget supply as a working plan if anyone would like to draw me one...

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  2. #2
    Senior Member snorkelfork's Avatar
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    Installing an m-Unit on your bike is about as straight forward as an install it gets. Without getting into the nitty gritty here's some info to get you started.

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


    1. Charging - This incorporates the wiring from your magneto or stator, Reg/Rec and battery. This all ties into the m-Unit at the 12V+ connection on the lower right side of the unit.
    2. Ignition - This is your Points, CDI, ECU which ever you have along with your coils, ETC. This will tie into the m-Unit in one place only and that is the AUX outlet on the m-Unit which provides power to this system.
    3. Ancillary (m-Unit) - The m-Unit among it's other features acts as a brain that controls voltage for everything on your bike aside from the charging system. This group also includes all of your lighting and switches, essentially anything that has an assigned input or output on the m-Unit.

    Print out several copies of your OEM diagram. Using markers, trace out on one page the entire charging system. On another Page trace out the entire ignition system. These will remain relatively un molested other than where they derive their 12V power from.

    Toss out any part of the wiring harness that doesn't involve the charging or ignition systems. The wire is old and it was low quality to begin with. Good wire in the lengths you need is cheap and worth the investment.

    Get rid of the OEM switches. They are one of the most common sources of electrical faults on these old Hondas and while they can be made to work with the m-Unit they will never work as they were intended. There are many options for momentary switches on the market now and some of them are very affordable.


    You'll also want to have:

    1 A good wire diagram for the factory connections (also take photos of connector backs for wire locations)
    2 Crimp Terminals that match the pins for your connectors
    3 Wire to replace and extend sections of the factory harness
    4 Main fuse, Gauge Fuse,
    5 Wire loom
    6 Heat shrink
    7 Solder and solder iron
    8 Time
    9 Patience
    10 Focus

    In my experience it 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 look perfect and simple, and having it all in vinyl wire loom. It’s much easier if you just wrap it all after the fact with electrical tape or split weave loom. The biggest tip I can give is to pick one thing at a time and work it out

    Break it down into bite sized pieces. 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.





    Geeto67 likes this.
    ...connoisseur of slack...

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    Senior Member jaguar's Avatar
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    Still REALLY unclear on what the heck these MotoGadgets actually do, and why they are SO expensive.
    Looks like little more then a junction box.
    I am Derby\'s Bitch


    Some times things come around that are so singularly inept it gives you a whole new appreciation for the ept

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  5. #4
    Senior Member miniman's Avatar
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    Quote Originally Posted by jaguar View Post
    Still REALLY unclear on what the heck these MotoGadgets actually do, and why they are SO expensive.
    Looks like little more then a junction box.
    It's a lot more than that. Actually a very clever little box of German engineering.
    Don't let the fact the hipster crowd uses them in abundance cloud your judgement.

    There are a good few videos online that explain them really well.

    In short
    All switch operate almost 0 volts
    Solid stat electrics for the flashers (no flasher module to go wrong.
    Built in protection and self diagnosis on on circuits in case of shorts
    Built in alarm
    Programmable lighting
    Optional rfid (keyless ignition)
    Works on 6-18v dc
    And much more. Like I said very interesting bit of engineering.

    Anyone with half a brain can wire a bike with one.
    Even if they fuck it up the unit will kill the power instantly and tell them using an led what circuit they fucked up on
    Geeto67 likes this.

  6. #5
    Senior Member jaguar's Avatar
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    interesting.
    I am Derby\'s Bitch


    Some times things come around that are so singularly inept it gives you a whole new appreciation for the ept

  7. #6
    Senior Member snorkelfork's Avatar
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    MiniMan beat me to the punch but I'll leave this since I took the time to write it.

    FYI, I work for a shop that installs them and sells them and I'm a believer. While their not right for every bike, if it's an older bike that you ride often and you rely on I believe it's one of the best steps you can do to have more ride time than repair time.

    It's a lot more than a junction box. It's a micro processor with solid state fuses being just one aspect. The recently discontinued V.2 and new Blue models have all the following features while Blue has a bunch of new optional features involving synching with your phone via Bluetooth.

    It removes voltage from the handle bar switches converting them into signal switches much like a computer keyboard significantly reducing the propensity for electrical failures at the handle bars.

    It auto detects shorts, turns off the offending system and a light on the unit indicates where the fault is in the system and resets itself when the issue is resolved.

    It's a sophisticated programable LED compatible turn signal relay.

    It's also has programable brake functions and allows you use a 2 wire LED light as though it were a 3 wire Running light and Brake.

    It has a built in alarm system.

    Built in Starter relay, but not Solenoid*

    Horn relay

    and more, here's a link to the manual m-Unit Blue
    Last edited by snorkelfork; 07-13-2017 at 03:49 PM.
    ...connoisseur of slack...

  8. #7
    Senior Member miniman's Avatar
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    Think of it in terms of carbs to ECU on an engine
    It's a BCU (bike control unit) rather than an ecu. It does everything for the bike using finely tuned electronics to make it reliable and better for everyday use rather than 40 year old electrics.
    Plus if you get the option m-button you convert the system to canbus, which means that all handlebar controls are operated through 1 wire.
    Reducing the amount of wires isn't just for aesthetics, the less wire means less joins which means less points for failure.
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    Last edited by miniman; 07-13-2017 at 04:17 PM.

  9. #8
    Senior Member snorkelfork's Avatar
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    No disrespect intended but I have to disagree with that statement. The m-button is actually very fragile and subject to any number of malfunctions and failures. It's extremely sensitive to EFI and can trigger functions you did not actuate. Often just one input wire will fail causing you to have to pull the entire component and all of your wiring vs just the one wire. There's no way to check continuity should you need to. And it's a hell of a lot more difficult to install that just running under a dozen 22 AWG wires tucked in sleeving through your bars, You can even use super small gauge multi conductor wire if you can source it.
    ...connoisseur of slack...

  10. #9
    Senior Member miniman's Avatar
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    When I got them I always use shielding on the config wire.
    This stops the rf interference.
    I will agree that they are delicate if installed incorrectly say reverse polarity.
    Thankfully the m unit is niegh on impossible to break with normal on bike voltages.

  11. #10
    Senior Member Geeto67's Avatar
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    so M-unit good, m-button bad?

    honestly I am actually blown away with how impressive this tech is, at least how the m-unit is described.

    I think the only problem I have is the expense. I can see this being easy to justify for a high end custom motorcycle from a lot of different standpoints, but for something like a $1500 cb750 honda the $350 cost provides a lot more value in the average ownership/use lifespan of a vintage bike. The one thing I like about old stuff is it is home reparable so despite being 40-50 years old I can still solder my starter switch to fix it, I can still rewire something with new wire, I can change a fuse box. If the M-unit fails 10 years from now what's my recourse? still will it be in better condition 40 years from now than my old fuse box?
    Ever tried. Ever failed. No matter. Try Again. Fail again. Fail better.
    - Samuel Beckett
    A tool is just an opportunity with a handle
    - Kevin Kelly

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