Kymco S125 no spark By jomama (Read 11,725 times)

[Bashan]

Well that's definately a DC powered CDI, the red wire comes off of the battery and ends up plugging into the two wire connector after running through the "combination switch":

There is no red/black AC power wire from the stator on this scooter, it's DC from the battery. The other two wires besides the trigger from your stator are AC feeds for the rectifier/regulator and have nothing to do with the ignition. The other wire in the two connector is probably a kill since it hooks onto a ground that runs to the coil and the TPS, whatever the hell that is. The four wire plug looks very familiar with the black/yellow powering the coil and the trigger wire coming in. The other two are grounds.

So testing the power wire to the CDI should be easy, turn on the key and touch the red probe on an exposed part of the wire and ground the black, you should get 12v DC. To test the trigger wire, unhook it from the CDI, set your multi to AC, put one probe in the end of the wire, ground the other probe to the frame, and crank the engine, from what I can tell on the PDF you should get 2.1v. Hook the trigger back up when your done. For the coil feed, unhook the wire from the coil, red probe in the wire, black to the coil connector, crank the engine. I'm not sure what you should get but I would think with the key on and the trigger sending a pulse, the CDI should be getting something to the coil. From the PDF it looks like 12v on that wire, maybe DC, I don't know. Frankly, this thing is undiscovered territory for me, I'm not sure what to tell you. Rich

[jomama]

As i explained earlier there are 2 wires that come from the stator, pink and yellow. I disconnected the plug and hooked the AC Volt meter across them and only got 14.4 vlts spinning the engine over. Everything i have seen so far indicates there sgould be 100 pls vlts. I does seem funny that its 14.4 vlts that is what the reading was across the bat terminals when the thing was run ning. Another mystery.

[Bashan]

No it's not a mystery, look on the diagram I posted off of your PDF. See those two wires coming up out of the stator that are labeled yellow and pink? That's what you tested, those are the AC feeds for the rectifier/regulator. The yellow usually powers the lights and the pink probably powers the battery after it's rectified to DC. If you put the multimeter probes in each wire you'd get an AC reading. Those two wires have nothing to do with your spark problem. That 100+ v AC wire your looking for is on an AC DCI which you don't have. Now, on most scooters the trigger coil is right over the flywheel as Sprocket's pic showed. On your bike it appears that the wire from it is harder to find out of the stator. It doesn't matter, unhook it and test it where it plugs into the CDI. 14.4v DC charging your battery is completely within normal limits, don't worry about that. Check the power wire going into the CDI and check the trigger wire going into the CDI. Rich

[sprocket]

The TPS is shown as a variable resistor or rheostat.. if memory serves... it is the throttle position sensor...

Honestly I think you need a Kymco mechanic

[sprocket]

Rich the pick-up coil on these is low and to the front of the flywheel at about 4 o'clock..

But these engines have a ton of sensors any one could be bad...

[jomama]

Well lads I performed the checks. Power into CDI 13.0 VLTS
Power to coil 0.1 ACorDC either way (should be 12vlts)
Trigger wire at CDI end 0.4 ( should be 2.1 VLTS)
So trigger wire and coil power wires are way belows specs.
even when i checke the trigger wire back where it makes its 1st connection from the unit, its the same so no loss between there and cdi. It Looks like a bad CDI 13vlts in but0.1 out to coil and a bad pulser/trigger at only 0.4 instead of 2.1 VLTS.

[jomama]

OK Lads, so i was about to order the CDI on the net. ( KYMCO PARTS123 .COM) This was a place in ohio and the price was $75.18 . Thats just about the going rate except when they wanted $23.99 to ship it UPS standard delivery. ( $99.17 total) I mean this thing weighs less than the average sandwhich . Insane shiping cost so just for the heck of it i called the local dealer and of course its not in stock but they called Kymco and all said and done it was $80.44 Tax included. Whoda thunk the dealer was cheaper. You really have to shop around. So when it arrives in a week and I install it i will post the results. Once again thanks for all the help .

[jomama]

I picked up the CDI unit today and as soon as it was installed, instant start and every time there after. Instead of just quitting like they usually do, this one chose to go gradually which made it so hard to isolate. Anyway all is good for now and once again thanks for all the help.

[sprocket]

Hey wonderful!

[Alleyoop]

Great Diagnoses Jomama, that sure was a bear to find, good job
Ride safe
Alleyoop

[sprocket]

Yup same thing...pulse, pick-up, ignition, hall effect coil, trigger coil... all the same

Your is behind the fan at about 4 o'clock