I have a 110 Tao quad. It was running great and suddenly one day it cranked and cranked, but wouldn't start. I found no spark at the plug. I did the "center pin" test on the CDI by removing the black/white kill switch wire at the 5-wire CDI connector. Still no spark, which leads me to believe the kill switch circuit is okay. The spark plug is fairly new, so I don't suspect it's the issue. I see others talking about checking the other circuits at the CDI, but I've yet to see a schematic that illustrates what wire is what at the CDI. So I'm lost on how to check the other circuits at the CDI. Does anybody have some tips about how to check this?

Thanks in advance,
M Ridzon

 

Hope these help. Other than what these posts show I know nothing on these Chinese machines.. Chinese ATV Wiring Diagrams - KazumaUSAOnline.com WIRING DIAGRAMS & INSTRUCTION

 

I did some diagnosis today. I previously mentioned that the kill switch circuit is okay at the CDI. Also at the CDI, the ground connection is good; it measures zero resistance to the battery negative terminal.

I measured resistance on the CDI connector for the timing trigger circuit. It measures 78 ohms to ground. Is this okay?

I also measured resistance on the CDI connector for the AC ignition power circuit. It measures open to ground. If I'm understanding, this is a problem. I pulled the stator off and measured resistance in the AC ignition wire between the stator and CDI; it was good, showing zero resistance. So I think the stator is bad. Can anybody chime in to confirm my conclusion?

Thanks in advance,
M Ridzon

 

Based on the fact that I've changed 5stators and one spark plug in the last year and zero CDI boxes and coils on chinese atvs and pitbikes It's a fair bet that the stator is bad.

 

My meter detected an open circuit on the AC ignition circuit. Should this have instead shown resistance on my meter?

Thanks again!
M Ridzon

 

I've never checked resistance, I measure the voltage that the stator puts out. I start with the stator and measure voltage while cranking the engine. Its a decisive way to find the problem, low or no voltage means bad stator. If it measures ok, just follow the voltage down the line and you will quickly find the problem

 

I'd like to get some assurance of the malfunctioning component, so I cranked the engine while doing some more tests. With the CDI disconnected, I measured AC voltage between ground and the AC Ignition Power terminal at the CDI. It measures approximately 35 volts. Is that okay?

Again with the CDI disconnected, I measured AC voltage between ground and the Timing Trigger terminal at the CDI. It measures approximately 0.15 volts. Is that okay?

I then plugged the CDI back in, and measured AC voltage between ground and the Ignition Coil terminal at the CDI. It measures approximately 0.035 volts. Is that okay? I realize an oscilloscope is needed to accurately assess the ignition coil activity, but I don't have access to that.

I'm curious to hear your thoughts and any other tests I may be able to run that would nail down the culprit with better assurance.

Thanks again!
M Ridzon

 

Open circuit on OHM readings and low voltage, your stator need to be replaced.
They cost around 10-20$ with shipping so it's easier to replace than to do more extensive measuring.

 

35v from the stator's exciter sounds pretty good to me, not sure if 0.15v from the trigger is enough, but with the trigger you don't need a big voltage. Your voltage at ignition coil is not enough, usually well over 12v on an AC ignition system, but that is produced by the CDI.

I prefer testing and replacing only what seems faulty, but sometimes the substitution method is quicker, and only a little more expensive on these Honda clone 50 to 150cc engines.

 

Update: I bought a new stator on eBay for $10. I installed the stator and now had spark, but it was weak. I pulled the plug and instead jammed a screwdriver into the plug wire and found that it arced strongly against the chassis, telling me the old plug was bad. So I then bought a new spark plug. Now the machine is running again!!

Thanks for the tips.