Kill button problem?

My 74 Commando was running great but the right directional was intermittent. I sprayed the assembly with contact cleaner then WD40. Directional is now fine but it shuts down while riding like you turned off the ignition. Then it will start up again. The wiring diagrams I've seen don't seem to indicate just how that red kill switch works. Anyone know ? Thanks in advance for any help . :twisted:

Oakland,

On my 1975 MKIII the kill switch breaks the power to the ignition system. If you suspect the kill switch just put a jumper across the wires leading to the kill switch to complete the circuit.
Best bet is to connect a volt meter to the power wire at you ignition and back track the wires. The circuit is basically: Battery to ignition switch: ignition switch to kill switch: kill switch to ignition system (EI or points). I would give you wire colors but I have found differences between my shop manual and what is actually on my bike. My bike is an early 75 and shares 74 and 75 components. Hope this helps.

Pete

Pressing the kill switch cuts the power to the ignition system but only when pressed if you release it power is restored. (Unlike most modern bike where you flick the switch to off)

It may be another bad contact inside the switch unit. Or maybe a failing wire (the infamous Boyer pick up if you have a Boyer is worth checking) or other bad connection somewhere.

I do have a Boyer ignition, but no problem until I cleaned the switch assembly - will check for good continuity on the kill switch first - thanks

Oakland850 said:

I do have a Boyer ignition, but no problem until I cleaned the switch assembly - will check for good continuity on the kill switch first - thanks

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The kill button can cause problems when running your E.I. unit through it. I had issues with my Tri-Spark and finally bypassed the switch and now the Tri is fed directly by the Key switch. Two friends in my Norton Club have had temporary failures with their Boyers because of corroded contacts through the kill switch. A well known Norton mechanic in the Michigan Norton Owners Club, highly recommends bypassing that switch.

The kill switch caused a voltage loss from 12.8 v down to 3.4 volts feeding the E.I. ....no ignition will run on that voltage.

The rinse method probably did not fully clean the corrosion. It's a spring loaded normally closed contact. Polish the contacts, check for broken solder joints, verify continuity. I had a turn signal contact get hot and melt/recede into the plastic, which allowed the rivet to loosen. A tiny dot of solder fixed it. Be caredul your 5 springs and single ball don't get lost when dismantling.

My kill switch operates a relay to feed Boyer via a fused relay so it always gets best voltage possible and the motor still stops with the switch. Fortunately the handle bar switches on my bike though old Lucas type are both clean inside an in good working order.

+1 toppy

There is too much demand on the ignition switch and switch assemblies. The main fused feed off the battery is also marginal at best. Use the ignition switch and controls to operate the relays and dedicated fused power feeds to supply the relays. IMHO this should include headlight, horn and as you have already done the ignition system.

Pete

I found a huge voltage drop through the kill switch. Since I never recall using it I simply bypassed it - one less problem.

JimNH said:

I found a huge voltage drop through the kill switch. Since I never recall using it I simply bypassed it - one less problem.

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Although we may think a killswitch is mostly used to shut off a motor when stopping keep in mind their are emergency situations where it can be of critical importance.

For example I had just installed a single Mikuni VM on my bike. Wound it up pretty good in second and pulled clutch to go to third and even though I'd rolled off the throttle the carb slide stayed full open! So engine winds up towards 6-7k. If I hadn't had kill switch handy and left clutch pulled I'd blown engine or reingaged clutch it would have wound out in second gear, blown engine and maybe me at 70mph.
Problem was too weak a carb spring. Solved by adding an Amal spring in addition to original.

I was real glad for that kill switch.

JimNH said:

I found a huge voltage drop through the kill switch. Since I never recall using it I simply bypassed it - one less problem.

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Good move!

I did what concours basically did with my handlebar switches. That is take them apart, clean them up really well and I also soldered all of the rivets to their metal surfaces. These rivets not only hold the switches together but they also conduct electricity. One thing that I did additionally was to put antioxidant grease on the switch contacts. Antioxidant grease is designed to work on wire connectors, it has zinc and graphite fillers within the lithium grease. So far my switches have been working really well.

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If you don't like the idea of using the kill switch that is in the normally closed position, you can bypass that switch and use the unused switch (starter) which is above the turn signal switch. This switch is in the normally open position. This will work with a Boyer Mark III and IV ignition system and a Pazon Sure-Fire system as well as original point type systems.Other systems may work fine, I am just not familiar with them.

1. If your bike is still positive ground with the Boyer or Pazon system, after you have bypassed the original kill switch connect the white/red wire from the handlebar switch to the negative terminal of the spark coil, the same terminal that has the black wire from the ignition module. Also ensure that the white/yellow wire from the handlebar switch is isolated from ground. Basically what you are doing is bypassing the switching mechanism in the control module so that the spark coils stay constantly on when the kill switch is depressed.

2. Now if your bike is wired negative ground and you are using the Pazon or Boyer system, you can use the unused switch (starter) as well. After bypassing the original kill switch disconnect the white wire that goes to the handlebar switch and then attach it to ground. Now connect the white/red wire to the spark coil's negative terminal - the same terminal that black wire from the ignition module is connected. Just make sure that the white/yellow wire isn't connected and is isolated from your electrical system.

3. If you are using points ignition and you don't want to use the original kill switch, you can use the unused (starter) switch as a kill switch. First disconnect the white/blue wire that connects to the white/yellow wire (that's the wire that goes to the handlebar switch). Then connect the white/blue wire to the connector that has all of the white wires in it. Now disconnect the white wire from the handlebar switch and run it to ground. Now connect an additional wire(s) from the white/red wire that comes from the handlebar switch to the plus terminal of each spark coil (the same terminal that the points/condenser wires go).

Of course to finish the job you would want to take the switch assembly apart and swap the buttons around so that the red button would still be at the top. The white/red wire was probably connected into the wiring harness. Just unplug it from the harness so you can attach the wire and hook it up the way I have described above. Don't worry about the white/red wire within the motorcycle's harness, it is just not connected to anything.

I got this idea from Boyer Branson's instructions for a kill switch on competition machines. What I described above is basically doing the same thing that they described but using the original Norton switch. I have tested this on both my BSA and Norton motorcycles. One has a Boyer and the other a Pazon system and they both work fine.

If anyone is not clear about what I am describing let me know and I can draw a diagram. The one advantage of using this switch arrangement is that even if the switch goes bad your ignition system would not fail. However it would be a good idea to test the switch from time to time to make sure it is working okay.