Got what might be a dumb question, but here goes...

How does the kill swith ground? And can I bypass it to test the ignition?

I should mention I am not using the main switch, so the black and white wire from the CDI box currently runs directly into the kill switch. Is there another wire I could/should run to the switch to complete the circuit?

I can't get her to spark. I've gone through all the entire ignition, and the Cdi box seems like the culprit, but before I order one from Rex, I want to make sure I didn't wire the kill switch wrong.

Other dirt bikes I've had have two wires going into the switch. This one only has the one. Just wondering how the circuit gets connected.

Thanks.

I have a new two wire switch. I checked it with the continuity tester. Both wires would go from the handlebars underneath the fuel tank near the coil. One wire would be grounded to the frame and the other would be spliced into - in between the flywheel points or CDI box to the coil. The two wire switches I paid $15 for it. It's not that much. In a panic situation you slam the switch with your hand and you're done. With a one wire switch you must hold it down until the engine dies. The one wire switch is spliced into the coil wire. Not the spark plug wire. The wire that goes from the flywheel to the coil. Somebody else might be able to explain it better. But I read the thread that DEET wrote that explained it very well.

asco

Hmm, I think I follow.

So assuming all other wiring is correct, if I run the black and white wire out of the cdi box to the switch, I should run a wire from the switch to ground on the frame.

So the circuit from the cdi is connected when it's grounded to the frame?

Your single wire switch grounds through the handlebars .
If you want to check that the kill switch is not stopping your CDI from firing ,
either unplug your single wire connection or take your kill switch off the handlebar .
With that done , and ignition key on you should get spark .
If not , possibly a dud CDI . DT 360's seem to have a bit of an issue with these .

Attached is DT 360 wiring diagram, it shows three wires going from
CDI to coil and kill switch. Orange goes to coil, black/white goes to one
side of the kill switch, black goes to other side of kill switch and to
ground.
Pressing kill switch connects black/white to black and stops spark.
Wiring it so you push kill switch and ground orange coil wire would also
stop spark but may hurt CDI ?
I'd check stater ohms and pulsar ohms before buying a CDI, there are
some discussions on how to test them if you use the search feature

All the Yamaha, and most other 2-stroke enduro/mx type bikes with points ignition kill spark by grounding the primary of the coil at the input side. Electrical current being lazy, much easier to go straight to ground than through the windings of the coil. The key switch and the "Kill" switch just connect the coil wire from the magneto to chassis ground.
Bikes with CDI have a separate grounding wire from the CDI unit that internally connects the circuits to ground prior to the capacitor discharge to the coil. Shorting the CDI pulse to the ignition coil could damage the circuits in the "black box".

To test kill switch and key switch in either case you just unplug the switch. Still no spark? Look elsewhere.

I got tired of the ground to bars and unscrewed the metal tab then threw a wire with ring into the same location and then grounds to the frame.

First of all, thanks everyone! Very helpful.

She sparks!!

Knowing that the kill grounds to kill the engine was super helpful and allowed me to work back from that.

I ran the a wire from the magneto to the CDI directly and disconnected the ground - bingo bango.... then spent a good hour figuring out where the harness was gounding... figured it out, and we are one step closer to lift off.

Again, appreciate the help. Saved me a lot of time and $

Brian

ok, and which cable or plug should I disconnect on my DT 250 MX to test the kill switch. any plugs or cables in the front light housing or under the fuel tank compartment ? There is a pair of blck/white cables that ar both connected to the ground scew of the ignition coil under the tank.are those cables coming from (on from the kill switch, the other from the ignition plate that is soldered to condenser ) ?

Regards
Frank