Measuring resistance through ignition system/ AC generator

[mjcharger]

Can anyone compare these results to a working bike? Does anyone see anything wrong

I'm still having problems with my project bike and have started looking into the ignition system. Using an agility repair manual I'm following its steps on how to troubleshoot the system.

I started at the CDI computer and measured the voltage going through the black and yellow wire going from the CDI to the Ignition coil. The voltage I get coming out of that is 4.8 volts with just the key turned on, and bounces between 7.5-8.5 volts while i'm cranking over the engine. Is this standard? I can't measure resistance with the multimeter I have.

Then working up to the Ignition Coil, the resistance between the ignition coil and the end of the spark plug wire is 8.48 kili ohms. Resistance from the end of the spark plug cap to a ground is 8.5 kili ohms. Voltage coming out of the spark plug cap when cranking the motor is around 20 mili volts. (THE REPAIR MANUAL SAYS RESISTANCE SHOULD BE BETWEEN 7～12KΩ)

I measured the resistance from the blue/ yellow wire that goes into the pulsar coil. When I connected that wire to the ground right next to the starter, it measured 6.45 ohms. Voltage was 7 mili volts. (THE REPAIR MANUAL SAYS RESISTANCE SHOULD BE BETWEEN 80～160Ω, SO SOMETHINGS NOT RIGHT)

I know the pulsar coil/ generator stuff is weird, but I wanted to try everything just in case.

Someone please help. My brains fried so I think i'm going to ride one of my other scooters and calm down

[sparko]

''Then working up to the Ignition Coil, the resistance between the ignition coil and the end of the spark plug wire is 8.48 kili ohms. Resistance from the end of the spark plug cap to a ground is 8.5 kili ohms. Voltage coming out of the spark plug cap when cranking the motor is around 20 mili volts. (THE REPAIR MANUAL SAYS RESISTANCE SHOULD BE BETWEEN 7～12KΩ)''

if you have these figures correct you should be good as that is the end of the line so to speak.

Not sure what you mean by
'' Voltage coming out of the spark plug cap when cranking the motor is around 20 mili volts.''

 I assume you mean 20 Kilo (20,000) volts. That is pretty good spark and means your secondary coil is operating correctly. I thought you said the spark plug was getting no spark in your other post? Is it firing now? Hope this helps. let us know. I don't see anything that doesn't match what my repair manual says. Maybe tomorrow I will check on my 125 but it seems to be right. If you are getting 20,000 volts at the spark you should be good. unless your timing is off. or the cdi is not working right. 

[mjcharger]

Sparko, thanks for the reply. I just re measured the voltage coming out of the spark plug cap and it was in between 34-35 millivolts. Not sure why it's up from the 20's the last time I measured it. Maybe it's because I charged the battery? But yes that's Milli.

I'm not getting a spark and it's not firing. It did a few days ago but now it's consistently not.

If I had a damaged CDI what would be the signs?

Thanks.

[sparko]

I think you will get more responses in the general section. But if you are getting 34-35 millivolts at the spark plug you are getting voltage, just nowhere near the amount you should be getting. the spark needs a lot more potential to jump the gap between electrode and ground. your secondary coil may not be working. I would check the primary coil first for continuity. disconnect the spark plug wire from spark plug. disconnect the two wires at the coil, they are on the other end of the spark plug wire. connect positive and negative terminals to your ohmmeter. if the primary circuit has continuity check the secondary circuit for continuity. My manual says ''set the meter to the K-ohms scale and connect the meter probes to the ground terminal on the coil and the spark plug terminal  inside the plug cap.'' The book says the reading should be 7-12 K-ohms.  I think you have already done this. I think you need to find how to check the cdi system. you should be getting a very high voltage spark (more than 20,000 volts but not in the 'milli' range, which would be one thousandth of a volt. you may want to check the voltage coming into the cdi. I do not know how the cdi is tested but if you have another scooter you may possibly interchange them. but if the wires have been chewed on you should probably check the continuity of all your ignition wires all the way back to the alternator. could be corrosion from rat crap and or water if the scoot was left outside. check the Ignition Control Unit as the book calls it. it is the area with the fuses and the cdi. look for corrosion and shorted wires. I will try to look at mine today but my schedule is really tight. post in the general discussion area too. Sorry I am not of more help but I wiil try to research more and get back in the thread. Gotta go buy dog food now. Good luck. 

[mjcharger]

I looked at the Ignition Control Unit and didn't see any excessive corrosion or loose wires. The fuses were ok and I tried starting again. It turned over but no ignition. I can't test the CDI but am tempted to go out and order one just to try it. What do you think?

[sparko]

''I started at the CDI computer and measured the voltage going through the black and yellow wire going from the CDI to the Ignition coil. The voltage I get coming out of that is 4.8 volts with just the key turned on, and bounces between 7.5-8.5 volts while i'm cranking over the engine. Is this standard? I can't measure resistance with the multimeter I have.
''Then working up to the Ignition Coil, the resistance between the ignition coil and the end of the spark plug wire is 8.48 kili ohms. Resistance from the end of the spark plug cap to a ground is 8.5 kili ohms. Voltage coming out of the spark plug cap when cranking the motor is around 20 mili volts. (THE REPAIR MANUAL SAYS RESISTANCE SHOULD BE BETWEEN 7～12KΩ)''

if you are getting roughly 8 volts going to the ignition coil and nothing to the spark plug, then I would say your ignition coil is bad. exchange it with another from a good bike , I am thinking they are somewhat interchangeable but can't really be sure. Maybe ask in the general section. But I forgot you had already checked the voltage going to the coil. And if your voltage jumps when you turn the engine over then the alternator seems to be in working order. Hope this helps and let us know. I think you are close.

[mjcharger]

Well I tried swapping ignition coils from a working Lance 50cc moped to the 125 and it didnt work. I tried swapping CDI's too and that still didn't work. Now when I put everything back on the 50 nothing works! Haha. Oh man. What have I done? 

[sparko]

I hope you checked the continuity of the primary and secondary of the ignition coil before you installed it on your 125. you can still do that as it has to be disconnected from the system anyway to test. your coil from the lance is probably still good. I will quote from my repair manual_' it is vital that the engine is not turned over with the plug cap removed and that the plug is soundly earthed when the system is checked for sparking. The ignition sytem components can be seriously damaged if the HT circuit becomes isolated." I believe if anything is fried it would be the cdi. check the ignition coil first for continuity and go from there.

you didn't say whether you had checked the primary winding of the coil. I assume it is ok as the secondary resistance seems to be ok. but for me it is still the prime suspect.

check those coils again for continuity in both primary and secondary windings. you said earlier that the voltage to the ign coil was about 8 volts so everything up to that point appears ok. make sure the coil is ok because the book was pretty specific about the ingition system components being vulnerable to open circuits. if the coil works the check the voltage going to the cdi again. if that is ok, and the coil is ok, then the trouble probably lies in the ignition box/cdi. fuses still ok?

''Sparko, thanks for the reply. I just re measured the voltage coming out of the spark plug cap and it was in between 34-35 millivolts. Not sure why it's up from the 20's the last time I measured it. Maybe it's because I charged the battery? But yes that's Milli.''

one last thing. I don't mean to beat a dead horse here but every source i have used says that a 'milli' volt is one thousandth of a volt. if your meter is reading this, unless I am wrong, or if you are in a different country and there is something I don't know, a millivolt is one divided by a  thousand volts, or one thousandth of a volt. I could be wrong.

mil·li·volt  (ml-vlt)
n. Abbr. mV
A unit of potential difference equal to one thousandth (10-3) of a volt.

I only post this because the reading of the voltage you posted was in millivolts not kilovolts

''kilovolt [ˈkɪləʊˌvəʊlt]
n
(Mathematics & Measurements / Units) one thousand volts. Symbol kV''

I hope we are on the same page and that the reading is what we are looking for. check voltage going to the ignition coil. If it is around 8 volts, it should be much higher after the ignition coil. once we determine that the ignition coil is good, we can go from there. This has turned into a very interesting (for me anyways) thread. Keep trying! Also, only work on one component at a time as then you can isolate things better. I wish someone else would comment on our progress. 

[Shaka]

The primary ignition coil (usually the black & green spades on the end of the coil) resistance should be between 0.1 - 1.0 ohm.  This is a very small value so you usually need to put your multimeter in the lowest ohm setting (mine is 200) and touch the probes together.  You will need to subtract this number from your reading through the primary coil.  This subtracts the resistance of your multimeter leads.

The secondary ignition coil (black spade to spark plug cap) resistance should be between 7 - 12 K ohm.  To set this put your multimeter on the 20K setting and place the red probe on the black spade and the black probe in the spark plug cap.

You can also test the resistance of your pulser coil.  This is what triggers the cdi to fire the ignition coil.  You unplug the blue/yellow and green wires coming from your stator.  Measure the resistance through them, it should be between 80-160 ohm.  Again use the low setting on the multimeter and subtract your lead resistance from the pulser coil resistance. 

If all of that checks out.  Your cdi is the culprit.  I've been dealing with a similar situation on my zx50 this week.  I'm hoping a new cdi will show up this afternoon! 

[mjcharger]

Shaka,

Here's what I have for my scooter. I have a solid yellow, solid white, and a blue/yellow wire coming from my straitor. I re- measured the resistance of the blue/yellow wire at the CDI and connected it to the the green ground at the battery. I got .4 Ohms for resistance. What does your scooter say?

I re-measured the resistance going through the ignition coil from the black connection to the spark plug cap and got 8.4 Ohms. Again what does yours say?