I am helping a friend with a butchered wiring harness (150cc quad) and have eliminated all interlocks except the handlebar switch and replaced stator and CDI box. ATV now runs, but won't turn off with handlbar switch.

On the 6pin chinese CDI's (square/rectangle connector), does the kill switch pin need to be grounded 100% to stop the spark?


With switch in OFF position, I have 3-4 ohms resistance on the kill switch circuit wire (to ground). With it in the run position it has no connection to ground (I suppose this is infinite resistance?). I assume there is some rust or poor connections in the handlebar switch? As long as I know that the pin should go to ground to kill the spark, I will test it with a jumper. Just don't want to fry the new box.

If that doesn't work, I guess will have to researh the pin out on the CDI I bought ;-).

I am using this diagram from resident Expert Lynn Edwards with the only difference being my CDI has square/rectangle plug, not rounded. I found another picture online that showed the same pinout for mine but can't find it attm.



Thanks for any input in advance!

 

3-4 ohms resistance to ground on the kill switch is more than enough to kill the spark.

Yes, infinite ohms is the same as "no connection".

Go ahead and short the kill switch pin at the CDI with a jumper. Be aware that there may be high voltage on this pin, so make sure you are holding on to the insulated part of the jumper wire.

To the best of my knowledge the square plug and round plug CDI's are the same except for the connector. I do not know if they also have mixed AC powered and DC powered versions. But you're getting spark so your CDI power is correct so your can ignore that aspect.

Let's say your CDI kill pin doesn't work when you short it to ground (I'm extrapolating forward). Try shorting the Timing Trigger pin to ground at the CDI. This will also kill the spark (and it won't hurt anything). This is a small signal wire, and the voltages and currents here are really low.

You could always cut the wire on your CDI Kill pin and wire it together with the timing triggger wire in the harness. Leave the kill pin on the CDI disconnected. Then the handlebar kill switch will kill spark (and stop the engine) by removing the trigger, rather than shutting off the supply inside the CDI. Both methods are valid ways to kill spark.

 

Thank you Lynn. You are a prolific and helpful resource!

I found the issue was that someone had dis-figured the pin inside the molex connector to the point where it wasn't making contact with the CDI pin even though it was snugly in the harness. sigh... Had a few connectors left from my stator replacement so spliced one in and now... stopping the engie is as gratifying as starting ;-)

Thanks!

Blufie

 

Hi Everyone and LynnEdwards,

A quick question for you. I have a CDi unit where the kill switch section is not working. Wiring for the kill and ignition is all ok (checked with multimeter on the black and white wire and the wire is earthed on the kill switch or the ignition). So, it's likely the "kill bit" of the CDI is faulty inside the box.

My question is how can I identify the wire that carries the trigger signal ? I read on one of your previous posts that shorting this wire into the kill switch wire (black and white) is an alternative way of killing the engine, and will then work via the ignition switch and kill switch as normal.

Any help appreciated

Simon

 

Firstly check your CDI is earth to kill, some are earth to run. If your CDI is faulty and won't switch off, Lyn Edwards was referring to the trigger or pulse wire, if you cut power from that to the CDI you will kill the spark. On many, one side of the trigger wire is already earthed, so if you short the other trigger wire to earth, you will kill the spark.

P.S. That pin out shown above isn't universal, some makers, especially Honda, have the power pin and kill pin reversed.

 

CDI is definitely earth to kill. Any suggestions as to how I can test to identify the pulse wire ?

 

Difficult, there will be several wires coming out of the alternator, usually one pulse wire will be blue or blue/white, blue/yellow, etc, but not always. An exciter coil wire is usually red/black, but again not always. Both these wires go to the CDI so you know one will be the pulse wire. The pulse wire generally produces less AC voltage than the exciter wire if you test them with a voltmeter (to earth), when spinning the engine over on the starter.