Part 4 - Rewiring

When the bike was purchased, only the bare essentials had been wired using the blue and brown wires from some mains flex. Naturally, this was removed. A complete harness was then built using new thin wall cabling. This proved to be a fairly simple task once the customised wiring diagram was developed.

The Ignition System

The bike came with all of the necessary components for the ignition. This included the short wiring stubs the connect between the electronic ignition, coil and magneto. This saved me some time. However, none of the other parts were supplied. For example there was no rectifier and no regulator.

The Magneto Generator

The stator on the TS250 contains three coils (actually it is four as the ignition has a primary and secondary coil wound on the same former). In my case the ignition coil(s) was simply connected to the electronic ignition using the original connectors. However, the two remaining coils, the lighting coil and the charging coil, needed some attention as there were some decisions to be made.

The Rectifier

The rectifier is responsible for converting the alternating current (AC) from the  charging coil to direct current (DC), suitable to charge the battery. The original TS250 uses half-wave rectification, which is a fairly crude approach, however, as it is  effective enough, I simply purchased a new Suzuki rectifier. These items are not expensive and an after market one would have been just as good.

Charging

The charging system involves taking the output from the charging coil and connecting it through the rectifier to the battery. The challenge is selecting the correct connection from the charging coil as there are two.

There is a yellow/white wire and there is a green wire. The yellow/white wire has a higher output than the green wire and is used when the lights are on. The green wire is used when the lights are off. Therefore, this means that the charging circuitry is routed through the light switch.

Buy the correct coloured cable.

Im my case, I have no lights other than a brake light. Therefore, I can keep things simple and simply use the green wire. The diagram shows the full circuitry for my bike, including lights, albeit without indicators. The circuit diagram was created by scanning one from a page of the workshop manual and then simplifying it using Photoshop.

Creating the Wiring Loom

For this I cheated. Once the wires were laid out across the bike, I use a product call Spiral Cable
Binding. This stuff is awesome and makes wiring a bike a breeze. The really good thing is that it makes it really easy to re jig the wiring loom when it is time to add the lights.

All ends were created using soldered bullets and were connected using the single and two way bullet connectors. These are simple to fit especially if you are handy with a soldering iron. Making a small wooden jig to hold the bullets can be a great help.

The Regulator

The regulator is designed to maintain a constant voltage irrespective of the speed the engine is running this helps the bike from blowing bulbs etc.

A regulator can be hard to come by as it needs to be an AC type. The regulator sits across the output from the lighting coil and the earth/ground. To date I have decided not to bother as I do not have any lights at the moment. However, having spent the first 20 years of my career in the electronics industry, I have a mind to build one. If I sort it out I will post details.

UK/USA Differences

The main difference between the US and UK wiring is that in the US the lights were designed to be permanently switched on. This means that the charging circuitry can be much simpler and does not need to be routed through the light switch.