Motorcycle Wiring and Connectors

Every motorcycle has an electrical system, even if it's nothing more than a magneto and high tension cable to the spark plug. Once lights are involved, and so the accompanying need for a charging system or direct light set-up, the motorcycle needs electrical cables and connections to unite the electrical equipment. With this article we look at some of the common methods of wiring connectors, a few of the horrors and the wire itself.

Unfortunately we can't see electrical current and a wiring diagram for even a relatively simple system, such as found on an early Honda C90 step-through motorcycle, looks already too much like city map. We can of course take the easy but more costly option of handing over our wiring issues to a motorcycle mechanic with experience in electrical-systems, but if we undertake an amount of reading on the subject , we will be able to complete wiring tasks on our motorcycles. And the mention of the city map can make a good starting point. Rather than become befuddled with the wiring diagram, think of the machine's components as destinations on a map and the wires as routes or roads uniting these destinations. It works for me.

Most motorcycle manufacturers' wiring diagrams carry a code system for the color (single or multiple) of tracer cable involved. Baffled as a small boy by a wiring diagram for a Honda C90 and – as they say – 'going off on one' my dad gave me a box of crayons and told me 'calm down' and to add appropriate color to each wire marked on the diagram. Task completed, the diagram looked 10 times clearer and much easier to understand. Using the appropriate colored tracer wires to unite the places (equipment) it was suddenly manageable and the joy of switching on the lights I'd wired, immense. Yes, it's a silly childhood story... but one which helps me even today with complicated modern wiring diagrams.
Often equipment is labelled: alternator, rectifier, pilot light etc. However, on occasions, symbols may be employed for switches snap connectors and earth connections; positive and negative poles will often be represented by + and - . Usually the diagram will carry a table of symbols to help.

While some motorcycle manufacturers labelled cables with identification colors, many use code letters. For example B = Black, U = Blue, N = Brown, R = Red etc. Not all motorcycle manufacturers use the same codes, but again tables are published as a guide.

After the Second World War, more and more European motorcycle manufacturers began adopting the German DIN standard and unless their equipment deviated from the norm, they usually didn't introduce their own variations. European wiring diagrams aren't often as clear, as components such as dynamo, coil, horn etc. were numbered. But again, the vast majority of diagrams carry a breakdown code so if you wish, you can label up the diagram to help.

Most manufacturers used tracer cable following the German DIN standard for both color and cross copper wire sectional area (inner) of cable. Meanwhile in Japan, most post Second World Ware diagrams use symbols; cases tables are again printed on diagram.

Some classic machines were wired with single color wires, often black. This can be confusing, but there is nothing to stop you rewiring with color tracer wires and coloring the wiring diagram to suit. Or, if you wish to stick to all black (or whatever), add colored flags at each end of each cable with pieces of colored insulating tape; on completion of the job and after checking, tear off tags.

For rewiring your motorcycle, appropriate cable choice is essential and above all household cable, even if it's thin, single or multi core, light flex or whatever, has absolutely no place on a motorcycle. Household wires are intended for 220 volt system in Thailand, whereas we motorcyclists are working with 6 and 12 volt systems and some very early electrical lighting equipment on a classic motorcycle may have been of just 4.5 volts.

Cables are graded in relation to the cross section of the copper wire. This grading is in relation to the number of copper inner strands or wire and the diameter of each strand. These rules apply to both Imperial and Metric defined cable.

When designing motorcycle wiring systems, motorcycle manufacturers chose cables which were the minimum size to do the job. They worked to a number of criteria of which two were/are vital considerations: One, the volt drop on full mustn't be too great; two, cable heating must be kept within specified limits.

While it may seem logical to us to use a thicker cable to lessen cable heating, often this is a bad idea, as the thicker the cable the greater the volt drop per meter of cable. Thus choices are seemingly a compromise, though motorcycle manufacturers made these choices for us in period and their selections remain sound.

Unfortunately some of the tracer wire color cable used on older motorcycles are no longer available today, but the electrical specialists in Chinatown are able to help with alternatives of an appropriate copper wire section (grade) with differing plastic out sheath color options or combinations of color.

While connectors are vital to unite electrical cables and equipment, and extra connections may be desirable for example to break/remake the circuit to the rear light which may have to be removed to facilitate rear wheel removal, it must always be remembered each connection point is a potential failure point.

Commonly, bullet, ring and Lucas style connectors are employed on motorcycles, or the wires – usually tinned with solder – are connected directly to wiring posts. Each type of connector has its roles; for example, bullet connectors united with snaps are the perfect method of connecting 'in cable' joints.

Today we have two methods of fixing bullets to cables and/or their inner copper wire – crimping or soldering. Both involve stripping a short length of the other plastic or rubber sleeve. Using a quality made crimping tool it's easily possible to achieve bullet or Lucas fits to cable, which resist all attempts to pull them off. Most motorcycle manufactures in the older days used solder-fitted such components and today you can repeat this if you prefer. In which case there is only one golden rule – never use an acid flux for soldering the connector, as there are risks of later corrosion which will compromise the connection. Instead, use 'electrical' cored solder which is cored with a resin flux.
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