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Discussion Starter · #1 ·
just picked up a 79 CX500 with 30k miles on it . I'd like to give a big shout out to all ye CX500 owners ! I've already met alot of you online




has the CDI ignition , things i've checked are . kill switch ok , starter button ok sending voltage to the yellow/red wire to solenoid when i push the start button(new Starter Solenoid coming in mail this ones not working) . when i jump the solenoid she cranks over fine but i get no spark .. shouldnt it be sparking? pulled plug and have it grounded to bike at a good ground. also i have cleaned the ignition coil connections on both coils to make a good ground. so my question is shouldnt it be sparking by jumping the solenoid? These are new NGK plugs .. old one not sparking either. I did also check for voltage at the coil wire connection before coil to see if getting any voltage to it .. nada. oh and i also did check the flywheel through the timing hole on the engine to make sure its turning .. yup its turning.





also i have read about the neutral switch . i do get a neutral light when electric is on . that wouldnt make it not spark would it? also checked the pickup coil continuity o/w wire to lt blue/white wire on the engine side. i also checked for some AC voltage at these wires when cranking by jumping the starter relay and its getting voltage there. Its cranking over fine , i even tried to jump it with my car battery still no spark so not battery related.





something with the CDI or Stator related me thinks ? oh also i did think of something else . i did have the front head light/instrument cluster on but it wasnt all hooked up with the ground. i have left it off unconnected until i paint it .. do i need that on and grounded right for it to spark ? just a thought , seems to me if i'm getting voltage at the starter relay solenoid when i push the start button it should be ok and crank over and spark eh? i have been wrong before tho .. once i think








looking forward to continuing this CX500 resurrection
.. haha any help apprieciated.





what my bad boy looks like now



Pic 1

Pic 2



when i get done with her it will look like this one



Pic 3
 

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You seem to have checked most items I could think of. The one other thing I thought of is the coils are mounted to the frame under the tank. Under their hardware, the frame is unpainted - to supply a good ground between the frame and the coils. If this was either painted over, or corroded, you could be experiencing sparking issues.
 

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Discussion Starter · #3 ·
You seem to have checked most items I could think of. The one other thing I thought of is the coils are mounted to the frame under the tank. Under their hardware, the frame is unpainted - to supply a good ground between the frame and the coils. If this was either painted over, or corroded, you could be experiencing sparking issues.




yup checked it when i read about that issue on the forum here.. cleaned very good and made sure they are getting good contact . I did check for any power coming to the coils themselves and i found none when cranking so i suspect its elsewhere.
 

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Sounds very much like a CDI




BTW What is your location? You may have a member here near you for an assist, like a



old but still working CDI from a replacement. Just a thought.



Rick
 

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Anyone know what voltage we should be getting from CDI to the coils when cranking?



I've been having the same trouble and have followed much the same line of inquiry as you. I'm waiting on a known good CDI. Post back with any findings and I'll do the same.
 

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There are wires that come from the stator to the cdi,they plug into the CDI under the seat, 1 of the plugs has a blue wire and a white wire, if you unplug that plug and test the voltage coming from the stator when cranking the engine over you should have 80 or 90 volts on the white wire and 100 or so on the blue wire.



If you get substantially lower reading on the white wire(less than 60 volts) there may be a problem in the stator.



There is another plug under the seat that has 3 yellow wires, they come from the charging windings on the stator and plug into the regulator/rectifier, you can unplug that plug and try starting the bike. If the bike starts with that unplugged then there is probably a short to ground in one of the charging windings.



If there is nothing wrong with the stator, you can do a quick test on the cdi, there should be approx. 150 volts on the pink and yellow wires coming from the CDI to the coils when cranking the engine over.



There are more thorough tests for the stator but try the above first and let us know what the results are.
 

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Discussion Starter · #10 ·
There are wires that come from the stator to the cdi,they plug into the CDI under the seat, 1 of the plugs has a blue wire and a white wire, if you unplug that plug and test the voltage coming from the stator when cranking the engine over you should have 80 or 90 volts on the white wire and 100 or so on the blue wire.



If you get substantially lower reading on the white wire(less than 60 volts) there may be a problem in the stator.



There is another plug under the seat that has 3 yellow wires, they come from the charging windings on the stator and plug into the regulator/rectifier, you can unplug that plug and try starting the bike. If the bike starts with that unplugged then there is probably a short to ground in one of the charging windings.



If there is nothing wrong with the stator, you can do a quick test on the cdi, there should be approx. 150 volts on the pink and yellow wires coming from the CDI to the coils when cranking the engine over.



There are more thorough tests for the stator but try the above first and let us know what the results are.






ok the results from testing the blue and white wires. Blue is almost at 100 volts .. white is almost 70 volts when cranking. still no spark when i disconnect the 3 yellow wire lead when cranking. also i did the continuity check on these 3 yellow stator wires under the seat on the motor side and when checking all them to each other all were pretty much consistant on continuity. all were getting continuity between them.





and i already checked for voltage coming from CDI to coils .. no voltage.





hey what should the voltage be on the pick up coil wires? the Orange/White and Lt Blue/white wires? thats AC voltage right? can i check that AC voltage to ground when cranking? ie: o/w wire lead to ground voltage ?







CDI or pick up coil me thinks eh ? sooomethiiin scwwwwwerwy goooin on heeeere. raaaaskaly waaabiiit
 

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It does sound like the CDI is causing your problem,,it would be good if you could find one to try on your bike to be 100% certain before buying another though. Or you could try your CDI on a known runner to test it that way too.




Did you try unplugging the kill switch? It is the black wire with a white stripe that plugs into the CDI.
 

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Discussion Starter · #12 ·
It does sound like the CDI is causing your problem,,it would be good if you could find one to try on your bike to be 100% certain before buying another though. Or you could try your CDI on a known runner to test it that way too.




Did you try unplugging the kill switch? It is the black wire with a white stripe that plugs into the CDI.




yup tried unplugging it .. no go .



what about checking the pick up coil voltage?
 

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Discussion Starter · #14 ·
Have you checked the voltage whilst cranking at the pink and yellow wires to ground?It should be around 150-200v DC.


yeah checked it no voltage from yellow or pink going to coils. I did just check if there was any voltage at the pick up coil wires when cranking orange/white and lt blue/white .. no AC voltage when i check them to ground while cranking. i did check voltage between these o/w and lt blue/white while cranking and there is some voltage when cranking between these two. shouldnt the pick up coil wires have some voltage to ground when cranking?





ok just picked this up off the net .. from what i understand you check the voltage between the 2 pick up coil wires o/w and lt blue/w ? and this should be .5 AC volts ? is that correct? what about checking each one to ground?







For a CX500, initial (easy) checks would be:



* sparkplug cap. In some versions, there is an arrester made up of fuselike carbon resistor with spring and rod. Illustrations here;

* ensure black/white wire from engine stop switch & ignition switch going to the CDI box does not read zero to ground or simply disconnect it while testing;

* check for pulsating low AC voltage (0.5VAC) from the pick-up coils, orange.white and blue/white wires;

* check for pulsating high AC voltage (90+VAC) from the exciter / stator coils. Detailed test shown here;

* in some instances, the ignition switch would be the culprit. Procedures here;

* or even as simple as a fuseholder as discussed here.













------UPDATE------: I retested the motor side o/w pickup coil wire to ground while cranking and there is a small amount of voltage there as the 0.5 AC volts specs suggest.
 

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Discussion Starter · #17 ·
Where did you get that checklist (web address)?




http://www.fixya.com/motorcycles/t3675523-79_cx500_doesnt_spark







ok just tested the pick up coil o/w wire to ground and got the small volts while cranking it talks about. also get a small AC voltage reading cranking while o/w and lt blue/w wires are connected with volt meter. so there is a small amount of voltage goin on here as what the 0.5 AC spec would suggest.

so now i'm leaning towards a prob with CDI module.





ok so are there any Cx500 owners in the Seattle area that i could try a good CDI box swap on it? you can contact me through my info here.
 

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Just installed an Ignitech (compliments of Cobram), but still no spark. I really thought that I'd put my finger on it too.



Still getting very weak voltage from the CDI to the coils when cranking. The battery is pretty weak and likely needs replaced, but I'm jumping it off my truck. Even still, I'm only reading about 10volts off of the black wire from the ignition key that I spliced the red Ignitech wire into - could my trouble all stem from a weak battery even if I'm jumping it?



Any thoughts on how I might salvage this situation would be much appreciated.



Thanks
 

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Discussion Starter · #19 ·
Just installed an Ignitech (compliments of Cobram), but still no spark. I really thought that I'd put my finger on it too.



Still getting very weak voltage from the CDI to the coils when cranking. The battery is pretty weak and likely needs replaced, but I'm jumping it off my truck. Even still, I'm only reading about 10volts off of the black wire from the ignition key that I spliced the red Ignitech wire into - could my trouble all stem from a weak battery even if I'm jumping it?



Any thoughts on how I might salvage this situation would be much appreciated.



Thanks




could be a short in the wiring somewhere too. just a thought.

did you run the tests for the stator coil? and pick up coil?
 

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could be a short in the wiring somewhere too. just a thought.

did you run the tests for the stator coil? and pick up coil?


Did resistance test on the stator coil, but haven't checked voltage on it nor the p/u coil while cranking. I need to get my battery charger back from a buddy and see if I can get a good charge on it. I intend to continue jumping to check voltages so as to not run it down - mistake?
 
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