wiring circuit

Its probably only me, but the wiring loom as described in the manual seems difficult to understand- largely because its not well labelled and in my case at least my bike has an entire extra generating coil completely missing from the diagram! Secondly, the wiring on my bike has been modified replacing the nacelle light switch with a simpler version from an NSU Quickly which necessitated re-routing the "kill" function. Finally my dip/horn switch is broken and replacements for this unusual 5-wire switch are not available. Consequently the loom will need yet more modification!

Here is my understanding of its function- I needed to get my head round this before I can hopefully try to modify it!

The most striking feature to my mind is the way the headlight bulb holder is used as a junction block to supply virtually everything.

Since there is no battery, in all cases power originates from the magneto/generator which in standard mode has 3 outputs:

a. HT to spark plug

b. Black wire to kill switch

c. Blue wire to t51 of light switch (lights and horn)

HT lead is obvious, it works and will not be considered further.

Kill (ignition off) Circuitry

The black "kill" wire presumably earths the low tension self-induction coil of the magneto thus killing spark generation. In stock wiring this black wire goes to t2 of the light switch. When the switch is turned fully clockwise to kill the motor, t2 is connected internally across the switch to t31 and a black wire extension links that switch  to t31 on the bulb holder which in turn is earthed. 

Kill switch circuitry as described in the manual- current flow for "kill" shown in green

In my bike the kill wire is detached from t2 of the light switch and diverted to an extra button that earths through the handlebars when pressed. The black wire linking  t31 on the switch to t31 on the bulb holder is no longer needed and has been removed. I'm assuming that this setup worked OK and as I haven't got the correct switch I will have to preserve it in some way in any new setup.

Horn Circuitry

Again looking at the standard wiring, power to both lights and horn is provided by  the lighting coil in the generator. I suspect this proved inadequate at some point since my bike is fitted with an extra coil simply to power the horn. However, I will consider how to deal with my setup once I have worked out how it is supposed to work in its original form so for the time being I'm considering the wiring diagrams as provided in the manual. 

In the standard diagram- power from the alternator is fed via a blue wire to t51 on the lighting switch which functions as a junction block to feed the horn via a silver/grey wire. Consequently this will be energised whenever the motor is running regardless of the position of the lighting switch. When the horn button is pressed current flows through the switch and horn and thence to terminal tH on the bulb holder by another silver/grey wire. Terminal tH then connects to earth. This is a junction block connecting the horn return to a grey wire leading to the horn switch (tH). When the horn button is pressed the moving contact is pressed against tH thus earthing to the handlebars completing the circuit through the horn and causing it to sound. Current path when the button is pressed is shown in green below.

Current flow through the horn when horn button is depressed (flow shown in green) independent of lighting switch position.

 

When the lights are "off"- i.e. switch straight ahead in the "run" position, T51 is still connected to the switch arm via an internal copper bridge which transmits incoming power to the moving terminal of the switch. This is then connected by the switch arm to an unnumbered terminal (51b?) and from here a brown wire connects to t51 on the bulb holder. This again acts as a junction block and continues to the horn switch tK which, when not pressed, is earthed via the handlebars. Consequently power from the alternator is simply dumped by constant current flow to earth which seems wasteful. However, the coils will generate power whenever the motor is running and presumably arrangements are needed to dissipate that power to avoid and damage to the coil.  Of course the  horn circuit described above will remain live, as it is independent of lighting switch position and the horn will still sound whenever the button is pressed and power is switched through the horn itself. 

The horn switch itself is very unusual for motorcycles which would usually have a single wire coming in from the horn, and earth this to the handlebars when pressed. The Quick 50 switch acts not only as a horn button but also as a current dump for output from the lighting/horn coil when the horn is not in use and this explains the extra terminal. In my case since the switch is broken I will have to replace it with a more conventional horn dip switch (3 wires) and thus I will have to arrange for output earthing in some other way or risk coil damage. Its further complicated since I have an extra coil purely to power the horn (prevents lights from dimming when the horn is operated?) which must mean I will need to arrange to dump output from the lighting coils too when the lights are not in use?

Note added. The lighting coilsxappear to have been upgraded to 12v, however thexseparate horn coil is still 6v and so a 6v AC horn is needed.

Lights

When the lighting switch is in the "run with lights" position (turned left/anticlockwise) power from t51 in the lighting switch is now connected to t58 in the light switch. This feeds power via a red wire to t58 in the bulb holder. This is a junction box splitting power to a silver/grey wire which supplies the rear light and earths through the light to chassis. Power is also supplied via a white wire to the dip switch terminal 56. This will connect with either 56a or 56b depending on position each feeding power back to the bulb holder to energise one of the two filaments in the bulb and thus to earth through the holder and chassis. Bulb filaments are not shown in the diagram. The second has current flow arrows added to try and make this clearer.

My own bike seems to solve the horn issue by having a separate supply from an extra coil. This means my bike has 3 wires emerging from the generator in addition to the HT lead. In my case these are black (kill),  green (lights) and yellow (horn). I describe what I did to resolve the lighting  switch and horn/kill functions in another post.