1977 RD400 Cafe Racer conversion project

There was a flash fire near the carbs and the original wiring harness was damaged beyond repair in the fire. The rest of the bike is still good and that is why I am rebuilding it. I found another wiring harness on Ebay for 35 dollars but I have heard good things about the simplicity of the M button and the junction box and switches. But, the price tag for it all is a good $400 dollars. That seems a little steep but it does seem like it makes things easier to wire back together. Another piece of my situation to consider, I am looking to swap out the original headlight for a dual LED headlight (two lights side by side that still fit in the original headlight cradle) so I won't have all the wiring space behind the original headlight like it used to.

There was a guy on here who built his own junction box. It was in one of Ichi's mod of the months posts. It wasn't expensive, it was really clean, and most of all it was easily serviced. I'll see if I can find it.

At the end of the day, you really just need a fuse box and the correct gauge wire/connectors to wire up the components that make the bike run (an M-whatever isn't that). If starting from scratch here are the things I would change about old junky motorskiggle electronics:

- Replace glass fuses with blade fuses. More common, easier to replace, take up less space. If I really wanted to spend the money I would look for a reset-able circuit breaker and never replace a fuse again

- change those old bullet connectors to more modern weather-pack connectors. Half the time chasing e-problems in an old bike is linked to broken connectors or bad corrosion.

- modern solid state electronics pieces. Forget points and old regulator/rectifier pieces, get a modern sportbike combo piece that is easy to replace on the road if you need it. Plus they will do a better job

- upgrade charging system. can't tell you how many old bikes don't break even charge till you are moving.

- sealed battery.

From what I recall of the RD350 which is the closest thing I ever rode or worked on to your bike, they are bone simple when it comes to electrics. My current ride is the polar opposite and has one of the most complex electric and electronics systems ever devised. From what I read on the M unit thingy it does away with relays and I can only assume that it does that by replacing them with solid state electronics. I just took a look at the wiring schematic that I believe applies to your bike and the only relay I cold see was is signal flasher relay. I was curious what the warranty for the M unit is and was unable to find any expressed warranty, just a form to request for service.

I'm with the woodsman on this one, you could probably hire a professional electrician to wire your bike from scratch for the cost of just the M unit and I'm not seeing that it does anything really special to address your wiring problems, it centralizes your wiring connection wherever you chose to locate the M unit and there is nothing to stop you from doing that same thing now, instead of using the traditional headlight shell location.

LED lighting is very cool looking and all that, but realistically anyone who choses to retrofit LED lighting to a 40 year old motorcycle currently comes under the heading of early adopter for that technology. Same as with lithium battery technology. People who pursue bleeding edge technologies are paying a premium to prove the worth of technology that is still in it's relative infancy. That generally spells big bucks and high risk. It might be the greatest thing since sliced bread or it might be a money pit, but it certainly won't save you any money off you household electric bill. Keep us informed how it all turns out in 5 years time.

ok it was 540Nova's central ground bar:

I mean...how freaking clean is this? It's pretty badass

If the M-gaget gets rid of relays, how many relays are we talking about here? headlight, horn, starter, taillight/brake?

still have to do something about the fuses and such.

Let's start at the beginning. Welcome.

RD400s are great little bikes. pretty fast,handle well for the time and are fun to ride. I have owned and modified a few over the years and am in the middle of creating an RD350 drag bike for fun.

Motogadget make some really nice parts and the M unit is a really trick unit. I have looked at them a few times and always decided to save those pennies for other more essential stuff. Wiring on a bike like an RD is simple enough but the stock system is adequate. If I wire a bike from scratch I like to wire in headlamp relays and an ignition relay and fuses for each circuit. I have used a couple of PC8 fuse panels from Eastern Beaver and I like their Sumitomo waterproof connectors and Panasonic mini relays. Main

You can also get electrical parts from

Motorcycle Terminals, Connectors, and Wiring Accessories and

OEM-Type Bullet & Spade Electrical Connectors for 1960's through 1970's Japanese Vehicles... Bridgestone, Datsun, Hodaka, Honda, Kawasaki, Landcruiser, Suzuki, Tohatsu, VW, & Yamaha

Products for flasher cans and rectifiers and LED bulbs

Oregon Motorcycle Parts Products for regulators/rectifiers and connectors.

Fortunately RD's are easy to work on and still lots of parts available from pipes to carbs to reeds and so on. A great place for parts is Economy Cycle in Winthrop harbor
https://www.economycycle.com/ good people and they sell mainly RD stuff. I just bought a pair of RD400 intake manifolds from John at Economy. Good people.