Kill Switch Question

[GaZBur]

Problem = I need to mount a tethered kill switch to my bike to be eligible for the Wyndham Street race.
The Bike is a Suzuki DR650SE. My question is - does the standard kill switch operate by breaking the circuit to kill the engine or by short circuiting the circuit to kill the engine. I know if I try to pull it apart to see it will probably not go back together.
If it is shorting the circuit to kill - my guess is that I can just wire the new kill switch up to each of the existing wires as they enter the switch.
If it is breaking the circuit then I guess I must cut the wire and add it in?
Have I got that right?

OK - I have bought a marine kill switch - only $15 from a Boatshop it has 4 terminals on the back. Two marked with a C and two with a M. The two opposing C terminals have also been marked with felt pen at the factory. My guess is these are the ones I wire for the switch.
Sorry if this sounds like an ignorant question but my knowledge of electrics is pretty much guesswork. I realise I could probably find these answers using a multimeter but don't know how to use one even if I had one.
If you can understand that and can help - thanks heaps!!!

[Jantar]

I think you'll find that by "Tethered" it means securely attached. The kill switches that work by short circuiting are generally fitted to magneto ignition circuits, and they simply earth the supply; ie ignition circuits that will still work even without a DC power source, while the ones that break the circuit are fitted to ignition systems that require a DC supply.

If you break the circuit on a system that normally earths then you have lost your kill function, and if you earth a system that breaks the DC supply you will either blow a fuse, or (more likely) fry your CDI.

DO NOT try to change your kill switch function.

[GaZBur]

No they mean tethered to the rider. If bike and rider seperate the engine must cut out. Seems to be a rule they put into "Supplimentary Rules" for street racing. Its like those ones on water bikes so when you fall off they dont keep going till they hit Chile and leave you to drown!
I gotta admit I don't understand what you said in your reply - does that mean I should take it into the shop so I don't fry something.
Thanks for you reply though!

[Jantar]

In that case you need to know exactly which system your bike uses. A simple way to tell is to see how many wires go to the kill switch. A single wire indicates an earthed system and two wires indicates a interupt system.

The old Suzuki two stroke dirt bikes used an earthed system, but all Suzuki 4 strokes I've owned were an interupt. I'm not sure about the DR650.

If it is an interupt then just wire it in series with the existing switch. I would need to see a circuit diagram of your marine switch to advise you if its an earthed system.

[GaZBur]

There are two wires going in. So I take it from what you say it is an interrupt system - meaning it breaks the circuit?
OK - if so then I think I understand. What I need to do is get the electrician at work to tell me which terminals carry a current in the set position and don't carry a current when the tether is removed. I can then insert it in relay by cutting one of the existing wires and inserting it there. Then either kill switch will work to shut off power.
Thanks Jantar!!!

[cooneyr]

I'm pretty sure it is an interrupt switch. There are two wires to the switch and I've had a look at the manual (you can get an electronic copy of the web if you haven't got one) and from what I know of reading wiring diagrams it is interrupt.

Best bet to figure out how to use the new switch is to figure out which to terminals are connected when the switch is in the kill position (or the teather pulled out). If you don't have a multimeter get a battery and bulb (pull apart a torch, get some wire and get somebody to hold everything together for you) and see which two terminals light the bulb when in kill and dont light it when in run.

You can use the bulb and battery setup with the existing switch as well. Does the bulb light when the switch is in kill (hope so) and not light when in run?

Cheers R

[GaZBur]

...If you don't have a multimeter get a battery and bulb (pull apart a torch, get some wire and get somebody to hold everything together for you) and see which two terminals light the bulb when in kill and dont light it when in run.

You can use the bulb and battery setup with the existing switch as well. Does the bulb light when the switch is in kill (hope so) and not light when in run?

Cheers R

OMG that is so obvious. Why couldn't I think of that! All that education wasted, all those years studying and I couldn't come up with something as simple as that!
Thanks - I will check it out tonight!

[NordieBoy]

Break to kill.

[GaZBur]

What Nordie says......

If you get stuck, tie the piece of string from your left wrist around both the HT leads and as you gracefully depart your bike the leads will tear out and effectively kill the spark........

"Gracefully depart" - you have not seen me crash obviously - gracefull it aint! However if i tied the string elsewhere I am sure my crash rate would drop drastically.

Thanks for the wireing diagram Nordie. Unfortunatley to me its like New Age Art. I know there are others who can appreciate it - but to me its just a bunch of squiggly lines on a piece of paper.

[Crisis management]

Electrickery 101 then....

Wot the little squiggles mean is that when the kill switch is in the on position (out, on the handlebar switch and the engine is running) the two wires that lead to the switch are connected to each other.....electrickery runs down one wire and back up the other wire and all is happiness and light.
When you depress the kill switch (as part of the graceful departure manouver) this connection is broken and the electrickery stops, has a chat and generally does bugger all, sits around and waits etc.

So, for your kill switch to work, you need a switch that is normally closed when the tether is attached and becomes open when you whip the tether out. This can then be fitted to one of wires to the existing kill switch and leave the existing switch in place if you wish.

By the way, DR riders are by nature elegantly dressed at all times and are expected to maintain a high standard of deportment regardless of the situation.

You had best practice a higher standard of crashing!

[GaZBur]

Almost got it sussed - thanks guys.
I have made an aluminium bracket for the switch attached to the handlebar clamp. I have used the "battery & bulb" multimeter to discover which of the terminals to use. Yes natually they were the opposite ones to what I originally thought. I have figured out how to make a waterproof casing out of an old 35mm film canister although it is a marine fitting it does not appear to be perfectly sealed. I have figured out where I can break the current line inside the handlebar mount so it wont be prone to weather or damage and that the switch must go in series with the existing set up. I can't believe something as simple as this caused me so much hassle.
On Saturday I will connect it all up - so on Saturday afternoon look for my next thread here entitled - "How do you put out an electical fire?"

With luck - this is one piece of equipment that will never be operated! I have had my quota of bins and injury this year already.

[FROSTY:Me]

Gazbur--dude for not much more than the marine kill switch you can buy a propper bike kill switch.Why not save yaself a load of hassle and run the kill to the ignition switch--the key one -find the power wire and run it off that --bingo

[scumdog]

OMG that is so obvious. Why couldn't I think of that! All that education wasted, all those years studying and I couldn't come up with something as simple as that!
Thanks - I will check it out tonight!

Go to Dick Smiths, Warehouse or whatever and get a circuit tester - looks like a pointy screw-driver with a wire hanging out of it.

A very, very handy item when dicking around with bike 'lectrics.

[NordieBoy]

A very, very handy item when dicking around with bike 'lectrics.

Thought you'd be a "wet finger" man.

[davereid]

Either a normally closed switch or a normally open switch are fine, for virtually any bike, regardless of the ignition system. If you have a switch that is normally open, use it to short the signal from the alternator. (Actually a secondary winding, hall effect switch, contact points or similar) designed to show the cdi or ignitor the position of the crankshaft.

If you have a normally closed switch, use it to open the circuit from either side of the coil.

Both ideas will reliably stop your bike.

Opening the circuit to the coil has the advantage that after you have done it, the coil draws no current, and will not overheat. On the other hand, the current required to energise the coil - 5-20 amps must go through your switch and its wiring.

Earthing the points or CDI input doesnt have this problem ,but some coil designs will overheat if the kill switch is operated and the ignition is left on. (points ignition systems are terrible for this.)