Soldering a Wire

A lot of times when you pick up an old CT90 some part of the wire harness may be damaged and need to be repaired.  While everyone who works in their shop or on bikes and vehicles knows how to solder to some degree, I thought I would provide a little electrical help and share how I go about soldering two wires together to repair a wire harness.

The first thing I will say is that if you plan on bringing old CT90's back to life on a regular basis keep an eye out for old partial wiring harnesses and pick them up when you can.  Being able to salvage sections of wire in the right color and with a pin or socket at the end always makes for a much easier and cleaner repair.

Some people may ask why not just use a crimp style butt connector to join two wires.  While a butt connector would work and be functional, it's not that clean and over the life of a bike I feel a nice soldered joint will hold up much better and less likely to give you a problem when your 10 miles up an old logging road.


The first thing to consider is making sure the final length of the two wires you are going to solder together will actually reach when you finally try and hook it up on the bike.  So before you start cutting and stripping wires make sure you add some extra length so you can screw it up once or twice and still have an acceptable length in the end.


Another thing that I always do to my soldered joints is cover them with shrink tubbing and I use a marine grade shrink tubbing from Harbor Freight. I like to use the marine grade shrink tubbing because it has an adhesive on the inner diameter that flows when you shrink the tubbing which helps seal the joint but also adds strength to the joint so the soldered connection doesn't carry all the load if the wire is pulled on.

Once you have all the wire length figured out and shrink tubbing available go ahead and strip about a half an inch or a little more off the end of each wire and cut a length of shrink tubing the will overlay each end of the soldered joint by about a minimum of a quarter of an inch.

Next slip the shrink tubbing over one of the two wires to be joined and slide it out of the way then take the two wires and overlap and then twist together so the ends wrap at least one wrap around the other wire being joined. If you wrapped the two wires enough you should be able to pick it up without the two wire coming apart. The length of the wrapped joint should be less than three eights of an inch long.

Next apply some liquid solder flux to the joint.

Next take what ever you are using for a solder iron or gun and apply heat to one side of the joint and then touch your solder to the opposite side of the wires.  What you are trying to do is have the heat that is being applied to the wire pull the solder through the joint so that it flows in-between all the strands of the wires so you have a strong electrically conductive joint in the end. Once your done soldering the joint its always good to try and clean any residual flux from the joint as it could lead to corrosion over time.

Once you've cleaned the joint slide the heat shrink tubbing back over the joint and apply heat until it shrinks up around the joint and then you should be good to go.

Helpful Links  (Shop Manuals, Wire Diagram, Model Information, etc.)