Kill Switch Question

[TomK]

I don’t have a kill switch on my bike, and shutting it off is kind of sketchy because my ignition switch (just a toggle switch-kick only) is buried behind my oil tank. I have to reach down between the fender and oil tank and feel around for it. Not a problem on startup, but not so easy when I’m sitting on the bike while it’s running (and can’t find neutral).

So, I would like to mount a kill switch on my handlebars. I have GMA controls (clutch and front brake), so the easiest, best looking option would be to add a GMA switch kit to one of them. The problem is that the switches are the standard spring-loaded, momentary push-to-close button switches and not rocker switches. So, I couldn’t use them as a run/off switch.

I’m no electrician, but shouldn’t I be able to run a single wire from my coil (where the points wire connects) to one contact on the push button switch and run the other contact on the switch to ground to work as a kill switch? Wouldn’t that ground out the coil and kill the motor? Any reason not to do it that way? 16ga wire would be enough to handle the load, right?

Thanks

[JBinNC]

IF you have a points & condenser ignition, then YES you can do that and it's been done millions of times. Hook up the switch to the point side of the coil.

You can also use it for clutchless, full throttle upshifts if you practice a little.

Jim

[TomK]

Awesome! Thanks a lot.

You shouldn’t have told me this, though.

You can also use it for clutchless, full throttle upshifts if you practice a little.

[JBinNC]

Awesome! Thanks a lot.

You shouldn’t have told me this, though.

I'm evil like that.

Jim

[TomK]

Kill Switch Install

I finally got around to installing a kill switch. After looking at the price of the GMA switch kit, I decided to go with a MUCH cheaper one from Lowbrow.

Here’s where I decided to mount it:


There’s room on the left between the grip and clutch lever housing.

I drilled and tapped the holes (#8):


It is a 2-wire switch but I cut one short to just ground it to the handlebars under the switch body. I tested it beforehand by running a jumper wire from the coil to the bars and it worked.


The hardest part was fishing the wire through. I used a white wire so I could see it and then spliced it to the switch wire and pulled it through.


Here’s the final result:

[TriNortchopz]

With that wire grounding on the handlebars, does ground go through neck bearings to the frame, or do you have a ground wire somewhere else between the frontend and the frame?

[Down]

With that wire grounding on the handlebars, does ground go through neck bearings to the frame, or do you have a ground wire somewhere else between the frontend and the frame?

Was just about to ask the same thing. You definitely need to run a ground wire to the bars ASAP if you don't have one. Otherwise you run the risk of welding your neck bearings and that is not good.

[DoomBuggy]

Maybe I've been lucky, but in 50 years of riding I've never had an issue with the kill going to the bars without a ground wire going to the frame

[TriNortchopz]

Maybe I've been lucky, but in 50 years of riding I've never had an issue with the kill going to the bars without a ground wire going to the frame

For a short interval such as a kill switch it may not be much of an issue, but if you have your headlight grounded only to the frontend, without a ground wire back to the frame, the ground will be through the bearings - not effective, and can lead to galling of the bearing... a ground wire would provide the path of least resistance.

[JBinNC]

H-D never used a ground wire back to the frame, until the evo era. Best to use a ground wire for the headlamp, to avoid the voltage drop through the bearings. There is not enough current through these systems to damage the bearings, so that is not an issue. For the ignition ground it is a non-issue on any grounds (pun intended HaHa).

Jim

[TomK]

Thanks for the knowledge. My headlight has a ground wire that I ran back to a common ground point.

[10scDust]

I have a 1973 FX I bobbed down with a round swing arm, old 2 piece K model bars, foot clutch, 2" under springer, etc.
I wanted to keep as much old school parts and effect as I could, it has a remote starter push button hidden in a side air scoop.

My dilemma was adding a kill switch because of trying to stop the bike going into a trailer, jockey shift and all, got hairy for me at times.
I was going to use the handlebar push button as an engine kill.
Here was my thinking, and I may be in err of it, and running an electronic Dyna S ignition in the cone.
I was afraid to ground out at the coil where battery side comes in because I figured it could weld the stop button, or worse after that said cause an electrical fire, I didn't try that.
I was also afraid I could fry the ignition module connecting on the other side of the coil, so I didn't try that either because I'd have to buy another module & wire it in.

So I connected to the spark plugs, that didn't work.
I figure the resistance of the wire to my push button acted like an amperage/voltage sink, drawing power from the plugs to make them spark.
If I got the engine running, just touching the wire lead to the spark plug killed that cylinder, this without a complete circuit to ground (i.e. the button not pushed completing circuit to ground).
So that is what I figured, high voltage/low amperage to the plugs, and the added wire robbed that spark signal. Still not exactly sure.

My next step was to eliminate the push button idea, as it was stock on the bars for a starter button, so I purchased a toggle switch to interrupt power to battery side of coil, via the switch. Like normal handlebar kill buttons work.
Only I wanted to keep the old vintage look on the bars and installed a headlight hi/low switch, such as those used on old FLH's.
Come in on the middle, go out on one side to complete circuit, the other extreme not used on the switch. It worked.

I am curious, are you running points/condensor, or electronic?
Also, where did you land the leads, at each end, to accomplish an engine ignition kill with a push button?
(Been following this thread, just now commenting on it) TIA.

[DoomBuggy]

The kill switch I used on both dirt and road bikes has been a momentary pushbutton circuit from the points side of the coil to ground. I've also mounted that switch on the bars each time.

When I was in the recent accident with the Panhead, I ended up partially under the car that pulled out in front of me with the Panhead on top of me running. All I had to do was reach out my thumb and kill the motor, then wait for someone to help lift the bike off of me. ( Hard to do yourself when your shoulder is under a car! ).

I have also seen where the switch interrupted the circuit between the ignition switch and the coil, this works just as well, but requires a 12v positive wire to and from the switch. I prefer the ground method above, but am not sure how that would impact electronic ignitions.

[confab]

You can also use it for clutchless, full throttle upshifts if you practice a little.

Jim

Okay. Now, that's pretty cool..

This sounds A LOT like a low tech version of the "Torque Interrupt Request" you see in modern automobiles.

In cars, you kill the engine for a split second (It doesn't really die and the operator doesn't even notice it during operation, but the torque output is reduced for a split second) while the shift is completed. Then, the power is back on and the effect is almost seamless.

It feels like a perfect shift.

I bet doing it by hand takes some getting used to, though.

[Guest]

piss easy to do just by a wuick drop of the throttle, been clutchless shifting for year, just gotta get the revs right & have fun