How to Repair a Wiring Harness of Motorcycle

Today we’re going to spend a little bit of time talking about wiring and connections, and the best way to keep your machine performing optimally, and if you run into a problem where a wire has been cut, or bad connection, or corrosion, the best way to address that and correct it long term. Now I’m going to show you a couple of things you should not do when it comes to repairing your harness, then I’m going to give you a couple of options as to a way you can repair it if replacing the entire harness is just really not an option for you. But before we dive into that, let’s talk about your battery connections, because that is typically one of the main areas that corrosion is going to take hold and then make it to where your machine won’t run properly or worse, than that won’t even start.

When you’re getting your machine ready to go for the season, and I’m sure you had a battery tender on it so your battery is good to go, you still want to go ahead and pull the positive and the negative leads off of the battery, make sure that the terminals are actually clean, usually with a wire brush.

Clean the post on the battery, reconnect them, and then it’s a good idea to spray them down with a high quality cleaner and protector. Yamalube makes a great product just for that. Next, let’s talk about fuses. Most importantly, usually when they pop, something went wrong to cause them to blow.

So just cramming in another one– especially one of a higher value– is not going to work out for you long term. These are sized for whatever circuit is on the machine, and if you just put in a larger one to keep it from popping, you’re stressing the harness that it was designed to protect, and you’re probably going to end up frying it. And talking about having to replace or repair something you don’t want to, try to repair a wire that is basically heated up and then burned into all the other wires going throughout your harness. You’re going to end up replacing the harness. There’s just no other way around that.

Now if it pops a fuse and you have the correct amperage in there, that is your machine saying, “Help, I’ve got a problem.

Figure out why this happened.” It could be a short, it could be an overloaded circuit…

whatever it is, you need to run it down because if you just cram in a larger fuse, you’re opening up yourself to damaging your wiring harness and worse than that, potentially catch your machine on fire. So just don’t do it. So what you need to do is take your time and figure out why that fuse actually blew. One other common mistake that I see is when people add on a light bar or sound system, they’re not paying very close attention to where they’re routing their wires. My rule of thumb is if you can at all possible, if you’re going from one end to the machine or the other, follow the existing wiring harness.

Whatever pathway the manufacturer took, it’s probably going to be safe from heat and or pivot points on the machine. It may look easier just to run it in a certain direction, but look what’s around it.


I mean if you’ve got exhaust or suspension pivot points, etc., any type of movement and or heat is going to affect that wire. Maybe not immediately, but it’s going to get to it eventually.

So rule of thumb is follow the existing wiring harness wherever you can. That’s going to be the safest route. Last but not least, you don’t want to tag on to the existing wiring harness. It was designed to carry the load for the machine and that’s it. If you are going to add a load, you need to separate that from the main harness.

The best way to do that is to use a relay. The relay is pretty much nothing but an electronic switch. You can use part of your harness to activate it and deactivate it, such as adding in on the light switch, but by doing that you’re only loading down what it takes to close that relay which the wiring harness can deal with. Now if you connect your new light directly into the existing wiring harness for the lighting system, you’re increasing the load to a level it was never designed to deal with. By putting in that relay you’re transferring the load from the main harness over to the battery where it needs to be to begin with.

Now let’s go through the scenario where you have a cut wire somewhere on your harness, and you’ve actually gone through the process with your volt/ohm meter to track it down, and you’re going, “Do I really want to have to replace an entire harness just for this one connection?” Well if you do it correctly, it won’t be a problem.


Let me show you a couple of things that you do not do. One my favorite you twist them back together and maybe just lay it over. That’s the worst I can think of.

Let’s go one step further. You twist it together, out comes the electrical tape or whatever tape you may have laying around, and then you do something like this. Well guess what? Any stress? Bang, there it goes.

Next another personal favorite of mine: wires are twisted together, look over in your toolbox and all you can find is one of these. No, don’t do this. Especially on an ATV or side by side, because all you’ve done is create a cup for it to fill up with water, or mud, or whatever, and then start corroding almost immediately. One step further: using a butt connector. Now there’s nothing really wrong with using a butt connector, but there’s a problem here.

Now you’re heading in the right direction, but with this particular style of butt connector, once you’ve made your connection, guess what? It is still opened up to the outside air so that is another place where you potentially have corrosion from water intrusion and/or humidity. Now let’s talk about the correct way to do this. This is a butt connector, but there’s a difference here. This is actually a butt connector that has a shrinkable tube around it.

So once you make your connections and get it crimped down, you would use a heat gun to shrink down the tube and that effectively seals the connection inside. Now it is important that you use the right size butt connector to do this and don’t crimp it so hard that you actually damage the shrink tube that goes around it.

Now this is a secure connection. It is protected from the outside environment, it can get wet, it’s not going to bother it. But we can do one step further if we want to truly have a professional connection.

This is my preferred method. What we’re going to do is use a section of heat shrink tubing. The real trick here is to go and put the tubing on before you start your connection. I can’t count how many times I’ve actually forgotten to do that in my checkered past. Strip these back.

The technique I use, we want to meet them about halfway and twist them over like this.

Now use a little bit of solder. Make sure that you get the connection hot enough to where the solder flows into the wire and not just globbed up on the outside. Let it cool down a little bit before you bring up the heat shrink, otherwise it’ll get caught you won’t be able to cover up the whole thing. All right, I think we’re good.

Now bring over your heat shrink, put the connection roughly in the middle. Now the other thing I want to recommend, the heat shrink that you used make sure it has a gel fill on the inside. Because when it shrinks down it’s actually going to heat up that gel and then it’s going to completely encapsulate your connection on the inside. I don’t know about you, but that’s the way I want to see my harness repaired, because that is not going to pull apart.

You’re going to break the wire trying to pull that apart.

But I know that this connection is going to last for a long time. All right guys, that’s going to wrap up this little video. Well listen, if you need any parts or tools for your machine, why don’t you come see us at and we can get you taken care of. If you’re having a little bit of trouble trying to figure out well what’s going on with your machine, drop us a line, send us an email, leave us a comment in the section below.


Perform general repair and maintenance work on motorcycles Assist with washing and detailing motorbikes Diagnose problems with motorbike transmissions Troubleshoot issues with knocking and shimmying Handle maintenance tasks on fuel lines and tires Perform fluid change tasks and ensure that bolts are lubricated properly Confer with customers to determine problems with motorcycles to determine issues Start motorbikes in order to assess impending problems Inspect motorbikes to figure out repair needs Work with apprentices and mechanics in order to diagnose and fix problems Perform both preventative and regular maintenance on motorcycles and mopeds Select appropriate tools to handle repair procedures

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