Topic: My kill switch just wounds

[chrismo]

The kill switch on my '76 CB550 doesnt work. When the bike is running, and I turn the switch from RUN to OFF, the engine slows down but keeps running. It will stall easily like this, but... I would expect that the kill switch should be a bit more "deadly".

It looks to be a stock switch. Any hints on what the problem might be? Is that switch supposed to stop current to the coil?

Thanks,
Chris

[oldbiker]

Yes, the kill switch breaks the feed to the coils so if it runs on there is a problem with the switch or there is a short circuit across the switch.

[oddmartini]

It's no problem to fix, unscrew the switchblock from underneath and separate the halves carefully - hopefully nothing will fall out... look in the top section, there's a blade contact that the rotating switch contacts - yours will be probably be full of crud. Make sure the keys are out, then clean the contacts with some lighter fluid, gunk off, petrol, etc on a cotton bud (q-tip) and try it out. I'd say there's nothing wrong with the wire to the switch, as it's TRYING to kill, it just has some moral problem against motorcycricide. The problem is probably in the switch.

[mark]

Did this ever get fixed or is it still a mystery?

It sounds like one coil is plugged in to the black/white wire from the kill switch, and the other coil is plugged in to the black wire that should feed the horn.

just curious. carry on.

[GroovieGhoulie]

My brother's K3 is having an IDENTICAL problem.  It feels like it's only killing two cylinders.  If I turn it at idle, it will slowly die, but when I hold some revs, it still runs.  It feels JUST like a mag check on a small airplane.  If I hold it steady at say, 3000rpm, I turn the switch and the revs drop to about 2500, turn it back, they raise back to 3000, turn it the other way; 2500.

I'll check out the contacts this weekend.

[chrismo]

I tried cleaning the contacts, but they looked fairly clean, and it didnt stop the problem.
I'm wondering if it might be a bad ground or something since my horn isnt working at the button either.
I was trying to figure it out tonight with a multimeter but boy does it get dark fast this time of year.

I'll be sure to post anything I find.

Chris

[mark]

Check the wiring at the coils. There are 6 wires coming out of the harness there. The big green wire is the ground for most of the bike, and should be bolted solidly to the frame. The black/white wires from both coils should plug in to the dual connector on the black/white wire from the kill switch. The blue and yellow connect the coils to the points. There is a separate black wire to feed 12v to the horn. The light green is from the horn button. The black/white and light green also have connections in the rats nest inside the headlight bucket.

It sounds like the kill switch works but is only turning one coil off. like it only has one coil connected to it. and the other coil is connected where the horn should get power.

Does the key switch kill the engine?

If the contacts in your kill switch were crusty, you should be having more trouble running than stopping.

Good luck.

[chrismo]

Excellent suggestion MadMark I bet you are right. I just took my horn button apart earlier today, and one horn wire is definitely plugged into a dual connector. When I pulled that horn wire out of the dual connector and grounded it to the frame - the horn would go off.

The key switch does kill the engine. I somehow missed your first comment about the horn wire mixup. Thanks for elaborating.  I'll definitely be testing that tomorrow!  Amazing that you diagnosed that before I mentioned my horn troubles!

Thanks,
Chris

[chrismo]

With this new information, I was able to fix my Horn & Kill Switch problems in about 5 minutes. And become more familiar as to what is going on down there.

Here's a pic of the wires now that they are in the correct connectors. Hope it helps someone else. Really it makes sense - the green wire goes to the green and the black to black for the horn...  The previous owner sure left me a lot of helpful ways to learn about my bike! Said his horn hadnt worked in a long time.

Thanks again for spoonfeeding me the solution!
Chris

[c15racer]

I dont suppose anyone has any pictures of what used to be here?

I'll check this black wire out tomorrow, i must have plugged in the horn wire!