MR BRIDGES' MOTORCYCLE DIARIES

YOU MIGHT’VE NOTICED A BIT OF A THEME EMERGING LATELY ABOUT FAILING TO GET TO MY WORKSHOP AND DO ANYTHING MUCH? I DID HAVE AN IDEA ABOUT GETTING THERE AND DOING SOMETHING A BIT PRACTICAL THIS MONTH, BUT THAT PLAN WENT UPSIDE-DOWN QUITE LITERALLY, WHICH LEFT ME WONDERING WHAT TO WRITE ABOUT?

Since I’ve been pondering a couple of wiring jobs I might as well have a look at the basics, and look at a few things that might be classed as ‘tricks’. At one point in my life, it seemed to me that looking at classified adverts’d be a lot easier if they had a section entitled ‘Just Needs Wiring’ as practically every unfinished, part finished, or hardly started project seemed to just need wiring.

I may’ve mentioned before that I don’t like spending money? So, back in the dim and distant past I worked out how wiring was supposed to work, mostly because all I could afford were those unfinished projects. It wasn’t always a great success, but it was definitely wiring, and most of the time it worked and didn’t catch fire. Strangely, one of the reasons it wasn’t always a great success was because I don’t like spending money, and I was utilising wire I’d recovered from a loom from a scrap yard, connectors that my mate was getting from work, and so on. It turns out that working with new materials that were designed with your application in mind makes things a lot easier and more reliable. It also turns out that the packs of connectors and rolls of wire that you see in Halfords and the like aren’t what you want at all. If you flick through the ads in this mag you’ll find one for Vehicle Wiring Products (0115 9305454), who will sell you cable (because apparently it’s not

called wire) a metre at a time in a large array of colours. Since most motorcycles aren’t going to have cable runs of more than two metres, and the 16.5amp cable is 41 pence a metre, then some twometre lengths in eleven different colours is going to amount to nine quid or so (although I’d get a bit more of whatever you’re planning on using as a colour for the earths). Okay, so that requires a certain amount of planning but, unless you’re confident, then wiring something is best approached with a plan anyway.

While you’re buying cable, then you might as well buy some connectors which, apparently, are called terminals, and not connectors. Don’t get the familiar red, blue, and yellow ‘preinsulated’ ones as they’re bulky, and weren’t ever designed for vehicle applications (Fig.1). Factory-style ‘uninsulated’ terminals, used with the correct crimping pliers, are hard to beat for custom motorcycle applications (Fig.2 & 3), and while there’re some better choices from an electrical point of view, those ‘better choices’ are a lot bulkier and harder to hide. Experience with aged Japanese motorcycles’d suggest that uninsulated terminals have a lifespan of around thirty years before they get to be too troublesome, which makes them excellent value for money.

What all this boils down to is that the oft-heard advice to just pick the original loom apart, take out the wire you don’t need, and rewrap it isn’t great advice. I think the two other big misconceptions are the fuse-box and heat shrink. You DO need a fuse-box because the fusebox is, in fact, the power distribution module, and makes life easier. Also, you should NEVER encase the whole loom in heat-shrink as it essentially turns the loom into a stick, and makes it very inflexible, which won’t help with the steering, and over-stresses the cables. Wrapping it in looming tape, or using PVC sheathing (Fig.4), will make for a happier, bendier loom or, if you really must, there’s nylon over-braid which lets the water in and isn’t very kind to paint or polished aluminium (Fig.5). It’s also best to check everything works before you wrap the loom. One of the things I’ve been thinking about wiring (with cable) is the KLR, which has direct ignition like a lot of small bikes. Usually this means you have a weird ignition switch that’s two switches stacked on top of each other. One of these does the battery-powered stuff, the other does the ignition. The ignition one works by running a wire to earth through the ignition part of the switch, closing the connection when the switch is OFF,

meaning that, yes, it turns ON when you turn it to OFF. Apart from being horribly unreliable switches, this also means that when some toe-rag cuts the wires to the switch, the ignition is, in effect, turned ON, and they can bump-start it and disappear over the horizon with it.

To get around that, and make things more reliable, I’m going to use a simple ON/OFF key switch, but run the earth for the ignition to the 30 terminal of a change-over relay (Fig.6), and earth the 87a terminal. All the ‘ignition’ switch will do then is power the relay ON (switched feed to the 85 terminal, earth the 86 terminal), moving the contact in the relay from 87a (earth) to 87 which could be connected to an engine kill-switch and hence to earth (or just left). The snag here is that toe-rags also know that twisting all the wires together often works, as it would in this case.

To provide some protection against that, instead of just running a wire from the main fuse, up to the switch, and then back to the fuse-box, I’m going to run an extra loop of wire up to the switch, and back, then earth the other end of the loop. That’ll mean there’s a good chance that cutting the wires to the switch’ll cause a short across the cutting blades and blow the main fuse and, even if that doesn’t do it, twisting all the wires together will. All in all, it should provide a bit more security as well as being more reliable. The same loop of earthed wire’d work equally well with a conventional ignition set up.

The other ‘trick’ is for making the handlebars cleaner, at the expense of slightly complicating the wiring, and uses, in this case, a VW Beetle headlight relay, although there are similar set ups on Volvos and Renaults I believe, but not necessarily the same relay. There are quite a lot of sets of very clean-looking switch gear on eBay that’re just push-buttons – that might be okay for working a horn, or as a start button (assuming they’d live with the current draw), but aren’t a lot of use for anything else unless you use a relay. If you saw my fiddling around with an Arduino to make a flasher unit, that works with push-buttons, as do HD flasher units, and the M-Unit type of control unit. If all you want to do is have the ability to dip the headlight, then the VW relay (which I’m pretty sure is also used on the Golf and Transporter van if you want to get a used one) is about twenty quid if you’re buying it new (Fig.7). It requires a separate ON/

OFF switch for the lights, and a live feed to the relay. The terminals’re numbered with DIN standard codes, so the 30 terminal is the live feed to the relay. The lights switch sends power to the 56 terminal on the relay, 56a and 56b are connected to the main and dip beams of the headlight, and the S terminal is connected to a push-to-make switch that’s earthed (Fig.8). In use, pushing the button on the ‘dip’ switch with the light switch in the OFF position will flash the main beam as long as the button is pressed, acting as a headlight flasher. With the light switch in the ON position, pressing and releasing the ‘dip’ switch will switch between beams with each button press. The dip switch isn’t taking any real current so a push-to-make micro-switch will work. These used to be about sixty pence each from Maplins, but Maplins is no more, and for most of us that means buying them online and suffering the postage (Fig.9).

The VW headlight relay doesn’t have a DIN standard terminal layout, and mounting it can be a bit of a problem depending on the version you get. Since you do need a fuse-box, and you can get indicator relays with DIN standard terminal layouts, then I’m quite fond of using the combined relay and fuse holder from Vehicle Wiring Products (Fig.10). Each one takes a relay, and three fuses, and they slot together to form a unit (Fig.11). There’s also a matching relay holder without the fuse ways. What appeals to me about them is that they don’t come with the terminals installed so, once the terminal’s installed, the cable’s connected to the fuse. Most other fuse boxes I’ve seen use a spade terminal, so you have the cable crimped to a terminal that slots on to the fuse-box terminal that connects to the fuse. The relay holder has a cable crimped to a terminal that the fuse plugs into, which is better electrically, and tends to be more compact. Another minor consideration is that the fuses are of the blade-type that seems to be the easiest to find these days.

There is one other ‘trick’ to reliable wiring, and that is to earth everything back to the loom. I still meet people that earth everything to the frame because it’s ‘less wires’, except of course it’s exactly the same number of wires – just considerably more connections, and it’s connections that usually cause problems, not wires.

Even Joe Lucas stopped doing that by the 1970s. I tend to run the wires a little long, and then add the terminals once all the wires are run – that helps to keep everything looking tidier, less confusing, and makes fault tracing easier.