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CX500 not sparking - Smoking top of Regulator

7099 Views 45 Replies 12 Participants Last post by  marshallf3
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.

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.
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.


Seattle area
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.

yup tried unplugging it .. no go .

what about checking the pick up coil voltage?
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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Where did you get that checklist (web address)?

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.


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?

yeah you can check these while jumping it just if you jump it using your truck dont start your truck just let it come straight off the battery , has a bit too much voltage otherwise. check the blue and white wires connector under the seat. your checking motor side connection , each wires AC volts to ground , blue should be around 100 volts , white should be around 80-90 volts while cranking.

pick up coil (bigger CDI module plug under seat) your testing the orange/white wire motor side plug and the light blue/ white wire same plug .. check them to ground should be 0.5 AC volts while cranking.

if you need a wiring diagram i have it online here. Honda 78-79 cx500 wiring diagram save the diagram to your computer and use your zoom in feature to get a good look at it.
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She's up!... sort of. Original CDI was at fault!

Ran through stator and coil tests again. Most of my values were on the high end of spec or just above. I was beginning to come to terms with the likelihood of an engine out scenario and then, on Cobram's advice, I decided to try jumping the bike with battery out in the event that a cell was shorted - I had mentioned that I was getting low voltage to the red wire on the ignitech. Battery out, the red wire was still reading very low. Digging through the posts I found Doward's description of how he used a double bullet connector to patch the red wire into the tail light wire in place of the little splicer the provide with the kit. Bingo! Double checked all my connections, gave it some choke and fired it up. Engine raced at full choke so I backed it way off. Idle is solid, but throttle response is choppy - this I attribute to the fact that I have my spare carbs on there and they're pretty buggy.

Tomorrow I'll run through my good set (they were leaking at the float bowl gasket - float level?) and get them ready to mount this weekend. Then new fluids and cleaning up the exhaust. Its still hitting the 90's here almost every day so i'm not so worried about summer getting away from me yet.

right on .. good to hear you found the issue. I believe its the CDI on mine too .. i found a guy near me that has a few extra CDI's so tomorrow i am picking one up. now i just wish i had the 90 degree weather ! do they sell that anywhere?

hey what is the red wire you speak of? and what wire on the bike side is this power coming from ? what color wire is it on the original CDI ?
Ironically, most folks around here are complaining about the weather. I try to explain that it only feels unbearably hot if the only time you spend outside is walking from airconditioned house - airconditioned car - airconditioned office.

The red wire is only relevant if you're installing one of the ignitech CDI (new aftermarket). A used oem will plug in just like your old one. On the ignitech the red wire, I believe supplies power to the unit. You splice it in at the brake light bullet (black wire) located near the coil and kill switch connectors.

Good luck with your CDI swap - seems like there's a really good chance that you're in for some near-instant gratification.

He's ALIIIIIVE ALIIIIIIIVE! got the other CDI today swapped it out and still no spark .. disconnected the black/white kill switch lead to the CDI under the seat and BAM! He's ALIIIIIIIVE nice blue spark
. too bad its too late to fire it up haha , its got no muffler so will be noisey , dont wana piss off the neighbors
Tomorrows the day!

kinda strange because i tested the kill switch and it was going on and off with power when i was testing it at the switch so not sure whats up with thtat switch maybe just need to clean up that bullet connector on this new CDI box . the CDI box bullet connection maybe, but it was indeed the CDI box .. thanks to all that helped me figure this one out
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I would try the other CDI again before you toss it.

There is no power from the kill switch, it grounds the CDI to stop the engine.

There may be a short in the kill switch wire. If there was a bad connection at the kill switch bullet connector it would be the same as having the wire unplugged, the bike would run but would not shut off when you turned the kill switch off.

or was it continuity i was talking about on the kill switch? i know i checked it and got a signal on and off when flipping that kill switch. have to look into that .. anyway heres whats going on now. got the bike to spark with that replacement CDI last night , left and right side was sparking .. then i re routed the CDI wire better reconnected and now the left side stopped sparking , right side sparks fine. swapped the right side pink wire to left side yellow coil wire and it sparks when connected that way but will not spark when connected to the correct yellow wire left side lead off the CDI .. so not sparking now on left side yellow lead wire coming off the CDI now. strange. going out now to try to trouble shoot it. redo the ground and check connections.

hope to get her started today.

UPDATE: ok just checked the voltage from the yellow CDI wire to coil and there is some voltage .. like 50 volts .. should be 150 ish? .. sooo what i'm thinking now is this battery might not be putting out enough juice to fire the plug. I'll recharge it so i know i've got a good strong battery goin.

battery spec is around 190 200 CCA so maybe this is it? Does the battery assist in providing voltage to the CDI ? or does it all come from the stator? also this CDI i just picked up could be going out.
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or was it continuity i was talking about on the kill switch? i know i checked it and got a signal on and off when flipping that kill switch. have to look into that .. anyway heres whats going on now. got the bike to spark with that replacement CDI last night , left and right side was sparking .. then i re routed the CDI wire better reconnected and now the left side stopped sparking , right side sparks fine. swapped the right side pink wire to left side yellow coil wire and it sparks when connected that way but will not spark when connected to the correct yellow wire left side lead off the CDI .. so not sparking now on left side yellow lead wire coming off the CDI now. strange. going out now to try to trouble shoot it. redo the ground and check connections.

hope to get her started today.

UPDATE: ok just checked the voltage from the yellow CDI wire to coil and there is some voltage .. like 50 volts .. should be 150 ish .. sooo what i'm thinking now is this battery might not be putting out enough juice to fire the plug. I'll recharge it so i know i've got a good strong battery goin.

battery spec is around 190 200 CCA so maybe this is it? Does the battery assist in providing voltage to the CDI ? or does it all come from the stator? also this CDI i just picked up could be going out.

ok Zegwin came over and we put his Ignitech CDI on it and got spark on both sides but it wouldnt start , fuel related we believe , maybe the carbs need cleaning now as this bikes been sitting a long time , they arent getting fuel into the pistons. we pored some gas straight down the spark plug hole and it sounded like it would start but didnt then after it ate up that fuel nothing so we think the carbs arent getting the fuel into to the pistons . so need to clean those carbs up now. I'm happy because at least now i know what the issues are.

UPDATE: you know i was working on it today and yesterday when we figured we had a fuel issue i was looking at the gas tank today (its off the bike and sitting on the ground) and i noticed the petcock was in the same position as we had it trying to start it . then i wondered why it wasnt dripping fuel all over .. turns out that petcock setting is NOT where the lever points but it has an arrow indicator and THATS where the setting is .. so we had it in the on position instead of reserve when trying to start it . so the little fuel i had put in the tank wasnt flowing in the on position! hahah wow. so it probably will start up after all if its set to the real reserve setting
wow. haha . so now i'm just waiting for a working CDI module.
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bad news guys . got another CDI module today went to hook it up and test it for spark and as soon as i hooked up the battery positive the bike started smoking. was smoking around the regulator , i quickly started to remove the battery connection but it burned up pretty bad.

ok heres what i believe happened. when i set the battery in the bike i didnt push it all the way in the slot and had a metal chain holding the battery in place so it wouldnt fall out and this metal chain was wrapped around a bare metal part on the bike frame. .. ok what i think happened was that chain holding the battery in place made contact with the battery ground , then when i attached the positive connection last it started smoking . so maybe the battery was sending power throughout the bike grounds ? i did notice the bikes ignition switch was in the start/run position at the time i connected the battery positive.

the regulator got very hot and was smoking around the top of it , wiring running to it maybe , until i could get the positive disconnected. was a real mess . but after i got battery disconnected i did notice the 2 red connector plugs below the regulator , the green wire was all melted at that right side larger red plug connector, the 2 red plug connectors below the regulator. also i did notice that when i connected this new CDI module i pluged the the coil wires up and instead of the yellow to yellow i accidently connected the bike side black/white kill switch wire to the yellow plug on the CDI module instead of the yellow coil wire , it was dark and i missed it .. uuugh i'm so pissed i did that but dont believe this had anything to do with the short . also i think it was smoking at the CDI module ground wire too .. and now it looks like the green ground wire is a little melted near the connector at the CDI box , so looks like some grounds were getting juice ? no idea.

anyways then when i tried reconnecting the battery after getting things sorted out the bike wasnt smoking anymore but it wouldnt do anything when hitting the start button. also would not crank over jumping the starter relay solenoid posts so i'm now thinking the regulator is shot or possibly damaged the starter motor.. would a bad regulator make it not even crank over now ?

oh wow big nightmare . sheeeesh . hope i dont have to replace the whole wiring now.

soo , i'm not the sharpest as far as electrical .. i know a bit but maybe someone can shed some light on what just happened! oh wow .. not cool at all. hope this new CDI i just picked up is ok. where do i start ?

UPDATE: ok thinking about this and the metal chain that had made contact with the battery ground wire .. wouldnt this have no effect as the battery ground wire is doing the same thing right? going to the bike and grounding the battery. so what about a bad battery ? could that have caused power to go to grounds when i connected the positive lead on the battery and had nothing to do with the metal chain contacting the ground post on the battery? or a bad Regulator rectifier ? it did not blow the main fuse near the battery that checks fine.
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Bummer,I hope that CDI box is still okay.

Almost sounds as though the batt connections were reversed.

Might think about starting a new thread in the tech section.

that is indeed what happen! i was looking at my battery today , its off the bike now and i had it reversed! can not believe i did that .. man i was sure i checked that before hooking it up . .lession in this is better to do it in daylight rather than in the dead of night! oh man .. now what ? probably fried the regulator eh ?

update: just checked the resistance on the stator all values check ok except the lightblue red wire to ground was 191 ohms should be 99 max per spec. looked at the wiring dirgram not sure what the lightblue/red wire goes to ,, stator ? i need to head to work after i get back will investigate the wiring for damage. i know it got really hot near the Regulator and wires leading to it. uuuuahg dam i'm so ticked i did that. hopefully the CDI box is ok i think regulator is prob fried. should i leave the regulator on to test it hooked up correctly or what? can you test these ?
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well after i checked the wiring i decided to try to hook it up .. the right way this time .. and believe it or not the CDI sparks .. i'm getting good spark. I did try to start it but it wouldnt start .. its been sitting many years so not surprised about that .. will try to get the fuel going to it tomorrow .

i'm just surprised the CDI still creates a spark after connecting the battery incorrectly running positive to the ground .

the ground wiring is melted in places but looks like it didnt burn through to any adjacent wires running with the ground wire so maybe i got lucky here.

it was sparking at least! she should start. tomorrow i'll try to get some fuel flowing into the combustion chamber.

stayed tuned ..
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If you're getting good spark then much of the electrical system is ok. That's very good news. The bike should run now, although there may be another issue keeping it from starting such as gummed up carbs, bad gas, clogged air filter, etc.

Since there are doubts about the regulator/rectifier, you can unplug it for testing. Obviously the charging system will not work but there will be one less variable to cause confusion while troubleshooting. You can always address it when everything else is working.

Are you certain the main fuse is installed correctly and is the proper value? With the battery hooked up backwards it should have blown quickly before any wiring was damaged.

The metal chain securing the battery sounds like an accident waiting to happen. Is the stock battery tray hardware missing? At the very least an insulating material should be used if there is any possibility of contacting one of the battery terminals - plastic cable ties, rope, whatever.

Any time a wire smokes there is a good possibility it has been damaged internally - the conductor may have fused open. This could result in an intermittent connection that could make or break under vibration. My preference would be to replace it.

If a wire has smoked or melted inside a wiring harness it's possible/probable that adjacent wires have had their insulation compromised. This can cause shorts, either hard or intermittent, that can be extremely hard to track down. The short could be buried deep inside the harness with no visible damage from the outside. In this case it may be best to find a replacement harness from ebay or a parts bike.

At this point, it would be advisable to clean up any wiring that appears questionable. Keep the regulator/rectifier completely unplugged. Try to get the bike running - since you have good spark, concentrate on non-electrical problems.

Finally, return to the charging system when it's running. If the wires are smoked on the regulator/rectifier my preference would be to replace it with a used one from ebay. Even after thirty years the Honda units are extremely reliable and I would not hesitate to install a used one.

You'll need a multimeter to properly assess and troubleshoot the charging system. See this writeup.

Thanks Dave , actually the grounding wires took the brunt of the flow and melted and broke open in a few places but i seen wires running next to the green ground wire weren't damaged so looks like i got lucky here.

how do i unplug the Regulator? your talking the 2 red plugs under the Regulator ? unplug both them ?

what amp fuse should this main fuse be? I'll check mine .. i think the regulator got very hot and might have taken alot of the flow before getting to thte main fuse maybe thats why it survived.

what is the conductor your talking about? you mean the ground wire terminals?

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hey craig any luck on the bike running yet??

getting close .. its a fuel issue now , its sparking fine now .. it was indeed a CDI issue .. Its not getting fuel into the pistons as the carbs are gunked up from sitting many years. i tried cleaning them myself but no go . so now looking at getting another set of carbs. stayed tuned
Least your getting it narrowed down! and glad things are turning out for the better. It is a great feeling once you get her running again after sitting for years. Good luck and keep us posted!

aaahg its back to not sparking on the left side .. will prob go for the Ignitec module and bypass the CDI all together they just arent that reliable.
Swap the coils side to side and see if the "no spark" followes?

Or at least swap the plug caps? ...could be an intermittant fault in the resistor/aluminum rod/spring combo...

yep already thought of that .. i switched the wires coming from the CDI to coils .. pink from CDI to yellow on the left side coil .. yellow from CDI to pink coil right side. the spark followed .. sparked on the left not on the right. so left side yellow connection coming from CDI not working , plus i already checked the wire itself for voltage before the bullet connection .. no voltage at all coming to the wire so indeed the CDI not putting out the voltage. left side coil and cap are ok .
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