I just acquired a Chinese 125cc ATV. Not exactly sure of the model, but I believe it is a TaoTao.

I did some searching through this site last night and found instructions to test it out.

Method 1) Unplug the CDI and remove the kill switch pin in the CDI connector on the wiring harness. The pin is held in with a spring tab on the pin itself. You'll have to probe into the connector and push this tab in order to extract the pin. Plug the CDI back in (kill switch wire dangling) and see if you have spark. - I used this method and still no spark

1) Unplug the CDI. In the wiring connector measure the resistance of the AC Ignition Power pin to the Ground pin. You should see 400 ohms or so. What do you measure? - 459 ohms

2) Measure the resistance of the Timing/trigger pin to the ground pin. You should measure 150 ohms or so. What do you measure? - 158 ohms

3) Leave the CDI unplugged. Set your meter to measure AC volts on the 100 volt scale. Measure the voltage on the AC Ignition Power pin to the ground pin while cranking the engine. You should see 40 to 80 volts AC while the engine is cranking. What do you measure? - 65 volts

4) Set your meter to measure AC volts on the lowest scale you have. Ideally this would be 2 volts but many meters don't go down this low. In that case use the lowest scale you have. Measure the voltage on the Timing Trigger pin to the Ground pin while cranking the engine. You should 0.2 t0 0.4 volts AC. What do you measure? - 224 volts, and yes I tested this one a few times to make sure, and the multimeter is a Fluke, I have seen it measure as low as .5V DC before

A) Leave the CDI unplugged. In the CDI wiring connector measure the resistance of the Ignition Coil pin to the ground pin. You should measure less than 1 ohm (but not zero ohms). What do you measure? - .001 ohms

B) Plug the CDI back in. Set your meter to measure AC volts on the 20 volt scale. Set all kill switches to the run position. Crank the engine while measuring the voltage on the Igntition Coil pin to ground. Poke through the insulation of the wire if you can't probe the connector. - I cant remember this one Ill have to measure it again when I get home


Any idea what would be causing such high voltages on the timing trigger pin? I would appreciate some input. Thanks!!

 

Tore the whole thing apart last night and checked every single connection I could find. Found a loose wire in one of the connections, and now I have spark. Got it started up and running pretty well.

 

Found this in the forum... If anyone knows what the issue might be? Thank you!

Method 1) Unplug the CDI and remove the kill switch pin in the CDI connector on the wiring harness. The pin is held in with a spring tab on the pin itself. You'll have to probe into the connector and push this tab in order to extract the pin. Plug the CDI back in (kill switch wire dangling) and see if you have spark. no spark

1) Unplug the CDI. In the wiring connector measure the resistance of the AC Ignition Power pin to the Ground pin. You should see 400 ohms or so. What do you measure? -open loop

2) Measure the resistance of the Timing/trigger pin to the ground pin. You should measure 150 ohms or so. What do you measure? - 144.4


3) Leave the CDI unplugged. Set your meter to measure AC volts on the 100 volt scale. Measure the voltage on the AC Ignition Power pin to the ground pin while cranking the engine. You should see 40 to 80 volts AC while the engine is cranking. What do you measure? - 45.8

4) Set your meter to measure AC volts on the lowest scale you have. Ideally this would be 2 volts but many meters don't go down this low. In that case use the lowest scale you have. Measure the voltage on the Timing Trigger pin to the Ground pin while cranking the engine. You should 0.2 t0 0.4 volts AC. What do you measure? - .166

A) Leave the CDI unplugged. In the CDI wiring connector measure the resistance of the Ignition Coil pin to the ground pin. You should measure less than 1 ohm (but not zero ohms). What do you measure? - 0.0

B) Plug the CDI back in. Set your meter to measure AC volts on the 20 volt scale. Set all kill switches to the run position. Crank the engine while measuring the voltage on the Igntition Coil pin to ground. Poke through the insulation of the wire if you can't probe the connector. -.002


any help is appreciated!

 

The first post shows the dangers of diagnosis by ohming out and checking voltages when testing ignition circuits, jeepwheelin thought he/she had 224 volts from the trigger coil, but the bike ran fine once a broken wire was discovered.

Incidentally some bikes only run when the Kill pin on the CDI is grounded, some only when the kill pin is not grounded.

 

Hey i bought a 2008 tao tao 250 and i just changed the complete wiring harness and my ignition coil has no power goi g to it but the wire is grounding fron cdi any help would be awsome

 

Hey all, I have a 250cc liquid cooled atv with no spark. I checked the ground at the coil and it's fine. There are 2 other wires that are connected to the coil.

I believe this atv has a DC CDI. It is double the size of the AC cdi boxes I've seen. It has a blue 6 pin connector housing with 5 leads inside. It does not have 2 separate connectors the the AC ones it just has one big blue plastic connector.

I believe the Stator and the CDI are working fine based on the voltage I pick up at the two wires supplying the ignition coil.

Here are the readings I found on the two wires supplying the coil:

- Black & red wire, Contant 12.95v DC as soon as I turn the ignition on

- Black & white wire, 0.12 - 0.23v randomly AC while I'm turning the engine over ( it seems like this is a pulse wire to tell the coil when to fire.)

Since I thought these readings were correct (at least I think but please correct me if there's something wrong) I moved on to measure the ignition coil resistance.

- Resistance between the 2 hook ups on the coil for DC & AC wires: 4.2 Ohms

Resistance from either the hook up (didn't seem to matter which one) to the spark plug boot: 20.2 K Ohms.

I thought these were within reason as well. But the ATV still will not spark.

I appreciate any help, I've been fiddling with this atv for 3 weekends now and I just want to get back on the trails.

Regards, Jack