67 Atlas ignition cutoff switch

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Feb 5, 2009
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I am rewiring and updating my 63 Atlas wiring. A previous owner had converted the ignition system to points and coils. The coils were located in the tool tray! Not to mention other issues. I bought a new Lucas wiring loom for a 67 Atlas. I have a new Lucas ignition switch to go with it. The Lucas loom matches the 67 Wiring diagram (Hooray!) I have relocated the coils to the proper location between the battery box and oil tank. The ignition switch is in the stock position by the oil tank. This makes it damned inconvenient to stop the motor in a hurry. The wiring diagram shows a "Ignition cutoff switch" that grounds the wires from the coils to the contact breakers. One isolated wire from each coil grounds through the switch.The new wiring loom has wires to accommodate this switch (or is it a button?) The coil end of the wires is obvious. The switch ends terminates with two bullet connectors coming off the loom up near the lighting switch. I would like to make this feature functional. But I have a few questions that need answered before I can go any further:

1) Is it a switch or button?
2) Is the switch mounted on the bars or of the plate near the lighting switch?
3) Who makes the switch and the part number?
4) Can anyone with an Atlas with a coil ignition post some pictures?

Any help is much appreciated.
 
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If your kill button shortens the contact breaker, I think a push on button shall be used. So that you don't have to remember flipping an on-off switch when trying to start it next time.
I prefer having an on-off toggle switch that cuts out power to the coils. Both on the racers and the street bikes. On magnetos the switch shortens the breaker and on the coil ignition it cuts power to the coils. I'd recommend going that route.
When throttle slide jams half open on a Manx in the middle of a tricky track section, flipping a toggle switch is much easier than constantly pressing a push button. Had to concentrate on avoiding fellow racers and keeping it on its wheels and not to leave the track. Also made it possible to raise my hand to notify the other riders that I was stopping.

Edit. WW1 warbirds had no throttle, so they used a kill button to moderate landing speed. Pressing it too long, engine died. Sometimes pilots too.
 
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There are reliability disadvantages to putting two switches between the battery and the coil. You won’t have to look far on this forum to find problems with kill switches in the ignition power feed.

A kill button that short circuits the contact breaker side of the coils sounds tricky to arrange without electrically connecting the two sets of contact breakers together, which is not what you want.
 
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There are reliability disadvantages to putting two switches between the battery and the coil. You won’t have to look far on this forum to find problems with kill switches in the ignition power feed.

A kill button that short circuits the contact breaker side of the coils sounds tricky to arrange without electrically connecting the two sets of contact breakers together, which is not what you want.
Exactly. But that is what the factory did if I can believe the wiring diagram. And the Lucas wiring loom follows the factory wiring diagram. Most likely I will go with a switch, not a button.
 
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If your kill button shortens the contact breaker, I think a push on button shall be used. So that you don't have to remember flipping an on-off switch when trying to start it next time.
I prefer having an on-off toggle switch that cuts out power to the coils. Both on the racers and the street bikes. On magnetos the switch shortens the breaker and on the coil ignition it cuts power to the coils. I'd recommend going that route.
When throttle slide jams half open on a Manx in the middle of a tricky track section, flipping a toggle switch is much easier than constantly pressing a push button. Had to concentrate on avoiding fellow racers and keeping it on its wheels and not to leave the track. Also made it possible to raise my hand to notify the other riders that I was stopping.

Edit. WW1 warbirds had no throttle, so they used a kill button to moderate landing speed. Pressing it too long, engine died. Sometimes pilots too.
You convinced me to go with a switch, not a button. I will still go with the factory setup of grounding each coil separately as this involves no modifications to the brand new (expensive) Lucas wiring loom. I just need to find the proper switch with the correct look and action. DPST in electrical terms.
I am aware of the WWI method of controlling engine speed. I was an autopilot technician on Vietnam era fighters when I was in the USAF. I still am an aircraft junkie. A friend told me the only hobby that cost you more than riding old Nortons was owning an airplane!
 

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