Lighting switch and Throttle control

Lighting switch - manner of operation

Although my repaired switch was functional- it wasn't ideal. In particular contacts that should not be connected in some switch positions (see on) were actually connected- all be it with a massively high resistance in the mega-ohm range. I decided to replace the unit and so bought a SO781 switch and new cap specified for the Tiger cub. Most switches of this type are sold with all 10 spades/pins. However, that for the tiger cub has only 9, like the FB original. I wondered how the lighting switch operates as there is little detail in the manual so I decided to determine which terminals were connected and in which switch positions and correlate this with the onward connections of those pins shown in the wiring diagram. Holding the switch so as to view it from underneath (pins up) with the gapped pin at 12 O'clock, I numbered the pins clockwise. The finger below indicates what I'm calling pin 1 and viewed in this way pin 3 is the battery power input. 

Tiger cub switch. Orientation adopted for this blog- pins up, missing spade at 12 O'Clock. Number clockwise Pin 1 indicated by finger

Pin onward connections are as specified using the wiring diagram in the owners manual and are given below, (note: I have also included wire connections made via the loom externally to other pins of the switch).

Pin 1: Power out to Headlamp (main and dip) and wire connection to pin 8 

Pin 2 Power out to Speedo lamp and tail-light

Pin 3 Battery power in

Pin 4 No connection

Pin 5 Power in from alternator (unrectified lighting coil). Wire connection to pin 7

Pin 6 To Ground

Pin 7 Wiring connection to pin 5 (unrectified lighting coil) power in.

Pin 8 Wire connection to pin 1 and power out to Headlamp main and dip

Pin 9 Power out- front parking light

Using my multi-meter I was then able to determine which pins are connected internally in the switch at each of the three switch positions:

Low

2-3-9; 6-7 connected

Off

1-2; 5-6; 8-9 connected

High

1-2; 7-8 connected

In addition to these internal pin connections within the switch and governed by the knob setting, some of the pins are also connected externally to each other through the wiring loom as stated above. Taking all these connections into account allows the switch to operate like so:

Low setting 

Battery power enters via pin 3 this is connected internally to both pin 2 (speedo and tail-light) and pin 9 (front parking). 

Pin 7 (Lighting coil power in) is connected internally to pin 6  which dissipates the output to earth.

Thus all sidelights (excluding speedometer light) are connected and operated from the battery. Obviously this position is intended for use when parked so there is no need for a speedometer light which would simply waste battery power. If the motor isn't turning there is no output from the lighting coils, but if it is then this output is diverted to ground via the inbuilt resistance wire. 

Off setting

Headlights (pin 1) connected internally to pin 2 (stop and tail-light) and connected via wiring to pin 8

Pin 8 connected internally to pin 9 (Front parking light) 

Pin 5 (lighting coil power in) connected internally to pin 6 dissipating power to earth. 

Thus all lights are connected together but there is no power to any of them- coil power being diverted to ground through the resistance wire.

High Setting

Pin 1(headlamp) is connected internally to Pin 2 (speedo and rear light) and externally by wire to pin 8.

Pin 8 connected internally to pin 7 (lighting coil power in).

Thus all the lights (inc speedo light) are connected together and all fed directly by lighting coil output via pin 7, the battery is not used. The feed will be unrectified AC voltage which will vary with motor RPM. I suspect this does not work too well since on my bike both the rear light and lighting switch control showed signs of heat damage.

Should add that I was really unimpressed with the headlamp bulb holder. This features three terminals (Hig beam/low beam/earth) in very close proximity- all are uninsulated bullet connections. The possibility of shorts seemed very high so I replaced it with a more modern bulb holder with better insulation and terminal spacing.

Original FB headlamp bulb holder- uninsulated terminals in close proximity

Replacement bulb holder

Throttle Control

In this bike as obtained the throttle control did work. However the cable was badly damaged lacking much of the outer cover, the twistgrip was loose on the bars and there was no friction lock control. I was able simply to  pull the twistgrip off the bars. Examination revealed poor cable condition and missing friction screw.

Throttle control as received- note missing cover to the throttle cable

Throttle twistgrip seen from below- no grub screw cable looks poor.

I removed the two Allen screws and separated the twistgrip from the cap segments. This revealed the cable nipple held in the rotating part of the grip. I will need a new cable which sadly is no longer obtainable so it will have to be made up using a universal cable kit.

Cable nipple inserted in rotating grip section.

Seen from above.

The cap section should have a friction grip plate which is pressed against the rotating section by the grub screw- sadly both were missing.

The grub screw is an Imperial size- which I didn't have. However it is slightly smaller than M5 so I was able to retap the hole to M5 and use a metric grub screw which I did have available.

Grub screw inserted

I made up a friction plate by cutting a length of steel to slip inside the control. I bent it around a steel rod of the same diameter as the twistgrip to obtain a smooth contour and then marked the position of the grub screw. I used a punch to impress a shallow detent in which the screw could locate. Reassembly and testing showed that the friction plate was functional.

Testing fit of the new friction slide

Friction slide marked with an indentation to act as a detent

Finally I rounded and smoothed off the ends of the friction plate 

The control could now be refitted to the bike to await preparation of a new cable.

Wipac Ducon horn and dipswitch

The existing dipswitch was a wipac ducon incorporating a horn button (earths power to ground via handlebars) which did work. The dip switch however did not work and all three terminals power in power out to dip and power out to main were always connected together. Dismantling the switch showed that the sliding copper contact which connects these terminals was detached.

Copper sliding contact removed note centre bend that accommodates the spring and the bent ends that locate on the slider.

Dip switch slider and copper contact that should be attached. Note spring in centre of the slider.

I think this switch is a make-before-break type that connects both lights temporarily before switching to any one position. This means the headlight i always connected during the dipping process since if it were disconnected then all power would be diverted to the rear light which would blow. I wasnt able to determine exactly how this works, but I noted the small spring in the plastic section and I believe that operating the switch moves the contacts into position connecting all three contacts, but releasing the switch allows the slider to pivot on the spring, disconnecting the main or dipped  beam according to position selected.

 It wasnt immediately obvious how this switch should work and I wasn't able to restore function. Accordingly I bought a repro switch and wired it as shown;

New switch installed

Wiring for repro Wipac Ducon switch

The brown wire connects to the violet wire from the headlamp nacelle. Headlight power (blue) connects to the pink wire from the lighting switch and the blue/stripe wies connect thee red power out to main and dip beam. The switch slips onto the handlebars with a rubber shaped grommet to protect the inside from moisture. I lead the cable into the nacelle ad connected with Lucas bullets