Confusion about how the kill button works

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JimP

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Hi, this is embarrassing, but I can't for the life of me figure out how the stock '74 handlebar mounted kill button is supposed to work!
I believe the button is "normally open", and that it is in the circuit that sends 12v to the ballast resister (the white/yellow wire).
Studying the workshop manual wiring diagram and Old Britts guides, it would seem as if the engine would ONLY run if the kill button was kept depressed!
I know that can't be the case. Where am I going wrong?

Confusion about how the kill button works


Confusion about how the kill button works
 
Hi There
It is push to break the ignition,and hold till engine has stopped.

Kev
 
Yes, that's what I figured, but I wish I could understand the "theory" behind it. The kill button on my Lucas handlebar switch is normally open until I depress it. I can't imagine how 12v are supposed to get to the coils. I hope there is a simple explaination I can understand!
Thanks, Jim
 
I would say N/C at the kill button. Simply put, pressing the button "open"s the circuit.

I swear to God, some of these things on the Nortons are just too simple for us to understand.

I ,myself, am a slow learner and fast forgetter.
 
Thank you for your responses. I wonder if I have a different design Lucas switches from another English motorcycle. Between the LH and RH clusters there are a total of four push-buttons, all of which are "push-to-contact" (see photos below). Do these look like the wrong parts? I'd like to find out now before I restore them! Jim P.

Confusion about how the kill button works
 
I swear to god some things on these Norton are too simple to live with, like the momentary kill button, when crashed mangled under bike so can't reach key and barely the bars with broken neck and elbow w/o hitting nerves that shut off lungs and heart beat so just a one extreme survival effort kill switch touch does not shut it off as gas continues to pour out on ya and over the points sparking under cover with a hole in it...

It should be an on/off period switch for me or such a switch added in too for me.
 
JimP said:
Hi, this is embarrassing, but I can't for the life of me figure out how the stock '74 handlebar mounted kill button is supposed to work!
I believe the button is "normally open", and that it is in the circuit that sends 12v to the ballast resister (the white/yellow wire).
Studying the workshop manual wiring diagram and Old Britts guides, it would seem as if the engine would ONLY run if the kill button was kept depressed!
I know that can't be the case. Where am I going wrong?

Confusion about how the kill button works


Confusion about how the kill button works
Click to expand...

The kill button is normally close circuit. That's why it becomes a problem when the contact gets dirty....the engine won't run. Another great British idea. :)
 
Jim, if both your switch clusters have two normally open (or push to close) switches, then you have two horn and high beam flash clusters. The other cluster (the one you don't have) has the kill and a dummy (inactive). You need to find another switch cluster or do what a lot of folks do and bypass the kill switch because they are a source of trouble.

Stephen Hill
Victoria, BC
 
While we are on the subject of Push buttons,...
What side should the Kill switch be on and what side should the Horn button be on ?
On my 72, the Kill is on the left hand side and the Horn is on the right.
The way my levers are set up, I have to let go of the Throtle to reach the Horn.
I think I would like to change that... Don't have a problem shutting the throtle to stop the engine...
Any thoughts...
AC.
 
My 2 Combats either came that way or I wired them LH kill and RH horn but you make sense switching hands unless trying to make muffler flame throwers or WOT kill tap shifts. OK a rolling back fire would be harder.
I'll have to face this tangled web this week but have put off re-learning its logic so not much to advise, but seems its possible to rewire switch functions pretty easy if slightly confusingly by crossed paths and colors.
 
AussieCombat said:
While we are on the subject of Push buttons,...
What side should the Kill switch be on and what side should the Horn button be on ?
Click to expand...

Norton Service Release N3/3

"Reversal of handlebar switch clusters.

Late 1972 Commando - all models.
Worldwide (for general distribution),
As a direct result of user requests for right hand operation of the direction
indicators, the decision has been taken to interchange the left and right hand switch clusters.
To save changing wiring colour identification at 6 connectors, the functions of kill button
and headlamp flasher and spare button and horn shown in Illustration 2 of the Riders Manual
are also reversed.
New prints of the handbook will include this modified layout but where motorcycles have been
despatched which are at variance to the handbook, the supplying dealer is requested
to acquaint the new owner with the revised layout. From the time of the changeover,
the revised control positions will be:

LEFT HAND
Top button - Headlamp flasher
Lever switch - Dipswitch
Bottom button - Horn

RIGHT HAND
Top button - Spare button
Lever switch - Direction indicators
Bottom button - Kill button

ACTION: Ensure that all new owners of modified models
are suitably briefed."
 
My June of 1972 combat has the lay out for the switches just as the bulletin describes.
I cleaned all my contacts while I had my switches apart. I use dielectric grease on all pivot points.
The point contacts inside the switch are thin and too much cleaning w/ emery will takethe contact surface completely off.
I had to have one wire, I forget which one resoldered as well. It fell off the back of the contact from fiddling with it and old age.
No problems to date. All signals, horn, dip switch, kill switch work as new. They do require some attention but then are good to go.
Be careful disassembling there is a ball and spring the center toggle switch rides on. A little grease will hold it in place on reassembly.
The lucas clusters are rediculously simple but patience on overhaul is a virtue. :shock:
Marshal
 
I just remembered. For all you go karters from the 70's.
Remember the L shaped spring steel on top of the spark plug?
It was attached via a head bolt to the head. You got off the kart and stepped on the flat spring steel stock to ground the spark plug and kill the engine.
Grab it once with your hand and you will never do the again!!! :shock:
In esssence this is what the kill switch button contacts do. They short the engine out.
Sorry, I didn't include in earlier post. :oops:
Marshal
 
OH Boy do I remember those touchy spark plug shorting tabs. I used to tell kids they could kill the engine by peeing on it too, some actually did, once...

Norton kill does not work this way it just cuts power to ignition same as key off or jerking battery lead off, no grounding or shorting involved, Boyer to points.

In Ms Peel a relay handled ign. power load ~5 amp max - so kill-key only handled relay switch current so crusting button contacts didn't have to strain to flow.
 
Thank you all,
I believe I finally get it. The important points for me are 1) the kill switch does work by opening the circuit, and 2) I've got a pair of "same-handed" switches!

Thanks again, Jim P.
 
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