Electrics. (Red)

I’ve been dreading and procrastinating on this part of the project for a while. When I was working on my cars as a teenager, I always kept electrical bits as simple as possible. I even stopped working on cars when they became heavily computerized. I never bothered to learn much about how relays, points, and the various circuits worked. It’s odd, because I never had any issues jumping into non-vehicular electronics projects. Something about the automotive aspect made them seem just a little weird. So, I have been delaying the wiring part of this project for a while. Time to just get it done.

One thing that the uninitiated will need to overcome is the excessive complexity of factory wiring. Even a basic motorcycle can have a surprising amount of wire and electrical signals that travel across multiple harnesses, components, fuses and connectors to complete. Add relays, switches, and 3-phase alternating current converting to direct current and you have a lot to process. What’s more, several components can sort of work if wired in different ways, so you can’t always assume you know what a circuit does without some study. Finally, if you’re taking everything off the frame, getting it all back in good order can be a heck of a job. Thankfully, there are modern options for those of us who don’t want to all the way down the OEM rabbit hole.

Since I was starting out with a plan to make a cafe bike, I had the idea of using a MotoGadget mo.unit system for this project. It’s a slick replacement for essentially all of the frame mounted electrical components using a very simple wiring scheme. Some good planning and you can end up with very little wire in your project. It also has some cool features like keyless start, an app, and some nifty configurability for lights. The standard version supports about a dozen circuits which is just enough for the essential components. Much more and you will need to do some planning. It’s a great project for a fully custom build. Red is not that, so I opted for a lesser known R21 option from NWT CycleTronics.

The R21, sold by EME in the US, is based on a more widely used X21 system and is arguably more capable than the mo.unit. It is designed specifically for Airhead models and has the ability to work with OEM switchgear, lighting, and other bits or, it can work happily with custom components. It appears a bit more daunting than the mo.unit at first, but it’s not too steep of a learning curve. NWT really shines here. Once you buy the system, you can send them the full inventory of electrical components you intend to use and they will create a custom wiring diagram for your project. On top of that, they are the gold standard for providing help during your build. I had several emails, a call or two, and one video chat to discuss what I was doing. Their customer service is simply unequalled.

So, where do you start? It’s a good idea to pickup a good quality wiring diagram for your bike in its OEM form. Even if you are ripping out all the wire, it will have some helpful information on wiring up any of the original components you intend to reuse. From there, build an inventory of what you plan to put on the bike in the finished project. From there, you can get your diagram from NWT or begin to design it all yourself.

Another decision to make is how you want to make connections in the system. I wanted something that was highly adaptable, durable, and relatively compact. After some experimentation with Mizu P25 connectors which are incredibly small and water tight, I chose to go with the larger Deutsch Connector DTM series. The DTMs are more durable the P25 and don’t require tweezers and a magnifier to assemble. If you under 40, this may not be as big of an issue for you. DTMs are a plug and receptacle system that are durable, water tight, and easily broken down for revisions. The only down side, is they are a light gray, so planning where connectors end up may be an issue if you don’t want to see them.

Finally, you need to have a strategy for grounding everything. This tends to add a wire to each harness unless you want to find a ground opportunity near the component. I chose to use a centralized grounding bus on the frame and routed everything to it. I just bought a copper bar and cut it to size, drilled out the mounting and grounding holes, and tapped them. This added some wiring clutter, but minimized the total number of connections to troubleshoot later. All of my harnesses are sleeved in expandable mesh, which keeps them orderly and compact while adding some protection.

Once all the key decisions were made, all that was left was actually doing the work. With the R21, this is pretty easy. You get input harnesses for the key switch, handlebar controls, and other miscellaneous items. You also get an output harness for the instruments and an output bus for other components. All you do is lay out the wiring, make temporary connections to verify the wiring diagram will work, then trim all the wire to add the connectors. Once you’re done, a handful of zip ties will keep things in place. In the end, I had a few revisions to make to work out some bugs but everything worked and it took a total of one week of my spare time. That’s about 12 hours going slow and steady, much of thqt crimping connections.

I’ll share that while the R21 is a great option, it does have a couple flaws. First, the outer enclosure it uses is 3D printed and feels a touch cheap. Everything inside is solid state and well made, but the thing reminds me of the result of a hobbyist rather than a production item from a company. Since nobody will see it, this is minor. Another criticism I have is the lack of technical documentation. You get a few nice PDF references for high-level install steps, but you will be out of luck if you want to know how it works. NWT will answer any question, but I think a good number of them would not be needed with more complete technical material. Even so, I would gladly recommend the R21 for others doing a similar project.