Motorcycle Wiring – 10 Pieces of Advice for Your Next Project

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So, I recently had the pleasure of re-wiring my entire motorcycle (1972 Shovelhead).  That might sound a little sarcastic but truthfully, it was a fantastic experience.

The bike’s existing wiring harness was a disaster, mickey-moused together in so many different ways.  Just looking at it was giving me an OCD-induced anxiety attack.  The tanks and seat were off the bike, so there really wasn’t a better time to tear it apart and start fresh.

If you currently have a big project going on with your bike, I would suggest considering whether it is also a good time to visit/revisit your wiring.  If you have a lot of the big parts already off the bike and out of the way, maybe it makes sense from a time-saving perspective?

Anyways, I have to admit that prior to this I had never rewired an entire bike.  Sure, I had wired up auxiliary lights, alarm systems, speakers, etc., but never gutted a bike and started fresh.  Instead of keeping this post in story mode, I am going to make a list of motorcycle wiring advice that hopefully will help you with your own project.

10 Pieces of Motorcycle Wiring Advice from the Shovelhead Wiring Overhaul

motorcycle wiring

(my big takeaways are in italics)

1) Consider your potential motorcycle wiring project in the context of other projects going on.  If you have a lot of big parts already off the bike, consider doing your rewire now while most of the wiring is exposed.

2) Get a good wiring diagram – motorcycle wiring can get complicated.  Clymer and factory manuals generally have them at the back.  The internet is full of them and this other post that I wrote rounds up the best ones I could find out there.  Don’t discount the hand-drawn diagram from a forum or other website.  Sometimes these are more intuitive and easier to follow.  I used one for my Harley.  I also suggest drawing your own diagram of your bike and storing it somewhere safe, especially if there is any customization involved.

3) Use Marine Grade Wire or some other high quality wire for your motorcycle wiring.  The difference between cheap wire and expensive wire isn’t much and it isn’t like you are trying to rewire an entire house or something you plan to do all that often.  The total quantity won’t be that much.  By the way, eBay was fantastic for this.  You can go to any autoparts store also, but I think the price/foot was better on eBay if you can be patient.  I bought the Lawrence Marine Products brand wire from Greg’s Marine.  My buddy Jeff in the coast guard actually recommended the marine grade, and I am grateful for it.

4) Make sure you understand wiring gauge (i.e. thickness).  Bigger numbers indicate smaller wire and smaller numbers indicate bigger wire.  For my Harley, for example, you can use 16 gauge for most things, 10 to 12 for the bigger things (alternator/generator), and 4 gauge on the starter/battery.

5) Get some good insulated connectors.  You will generally need butt connectors, female spake connectors, and maybe a few female spade connectors.  For this, my preference has been Home Depot and Radio Shack.  I find it best to just go there and look through what they have.

6) Get a good pair of ratcheting crimpers.  I bought the Titan Tools Ratcheting Crimper off Amazon, and I have been very happy.  Sure, there are many makes and models out there, but so far these guys have been great.

7) Get heat activated shrink tubing.  Not only is it great for cleaning up the terminal connections, but it is also so much fun to play with.  For this, I suggest going to Home Depot again and getting a spool of uncut consistent diameter tubing.  In other words, lots of the same diameter.  There are tons of variety packs out there that are going to seem very cheap at first, but most of what you will get will be useless (too small or way too big) for motorcycle wiring.  Also, it will be cut into short sections and so there is not way to cleanly insulate a long section of wire.  From my experience, most runs of wire will be one or two wires together, so you need the same diameter shrink tube in most spots and potentially several uncut feet.

8) Get a heat gun.  I also recently bought a Wagner Heat Gun and have been very happy with it.  It even helped me heat up a stuck bolt the other day.

9) Use a terminal board or other way to organize the wires.  You can buy miniature terminal boards at Home Depot and Radio Shack. You might think you can do without, but it keeps things organized and makes certain complicated wiring intersections much easier.

10) Before you start ripping out the wire, I would suggest labeling each end of the wire with masking tape and a sharpie.  Then replace each wire one at a time.  The existing wiring harness might be in bad shape, but the information you can gain from at least seeing where the existing wires go is invaluable.

That’s it folks – my best pieces of advice on motorcycle wiring.  Now go have some fun.  You will be amazed at the feeling of satisfaction you will get at knowing every wire on that bike was run by you!

P.S. If you need a wiring diagram for your motorcycle , you can either (1) check out my post on free wiring diagrams, where I list the best sites for free diagrams, or (2) reach out to me directly, and I will see if I can provide you one.  If you liked my post, please share via social media.

Didn’t find what you needed in this particular post?  Check out the HappyWrench Motorcycle Repair Link Database.  It is a one-stop shop for all your DIY motorcycle repair information needs.

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