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Discussion Starter · #1 ·
I traded for a 79 Custom which turns over but won't start. I checked for spark and nothing. Changing out the coils seems pretty easy, but Honda is closed on Mondays and I'm wondering if they will even have these old parts.



I'm used to working on Honda 90s and there's a website called DrATV that has most parts I need. Is there something similar for the CX500? I've been searching around online and can't seem to find a good source. This CX is 10 years younger than my 1970 CT90, yet it seems that parts may be more of a problem.
 

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Hi Scott,

I've used the 'Bay, BikeBandit, and sellers from this forum to get parts, and seldom have bad experience. Once in awhile I go through Parts Unlimited at my local Yamaha dealer, but that's partially due to the cute girl who works the parts counter.




Unfortunately I'm more familiar with the transistorized system used on later CXs and GL models. Some searching should find several threads that will walk you through troubleshooting your trouble with the CDI ignition system. Is there no spark on both sides? I wouldn't put money on both coils being bad at the same time, you might be close to throwing some money away.
 

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Hi,

I would be surprised if both of your coils are bad,,they could be but there are other things that are more likely. Faulty kill switch, CDI or stator come to mind.

How are you checking for spark? The valve covers are made of aluminum, when you test for spark hold the plug against the engine hangers or frame.



There is a black wire with a white stripe on it that comes from the kill switch and plugs into the CDI (black or gold colored box under the seat), try unplugging it at the bullet connector and test for spark again.



If you still have no spark I would try unplugging the yellow and pink wires coming into the coils from the CDI to see if there is voltage on them, there should be around 150 volts DC when rolling the engine over on the starter.

If you have no power there then you should check to see if there is power coming into the CDI from the stator. There is a plug with a blue and white wire that comes from the engine and plugs into the CDI under the seat. The blue wire should have approx 100 volts AC on it and the white should be 80 or 90 volts AC when rolling the engine over on the starter.

Try these tests and then let us know the results.
 

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Before you buy new coils, make sure they're properly grounded first. The coils ground through that hanger that wraps around the frame. If it's rusty under that hanger, the coils won't ground and your plugs won't spark. Coils are relatively simple devices, with no moving parts, so they shouldn't fail unless they get cracked open. I had the same problem with my 81 cx500, and it turns out it was a combination of the spark plug caps and rust under the coil hangers.
 

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The valve covers are made of aluminum



With about 1/10" of clear coat on them.
 

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Discussion Starter · #7 ·
I just checked again and no spark on both sides with plug grounded on frame.
 

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Another thing to check is the condition inside the plug caps, the resistors inside could be corroded.  Replacing the resistors with a solid brass section can help the ignition.
 

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Discussion Starter · #9 ·
I just tested both sides by pulling the spark plug, replacing it in the spark plug cable and grounding it to the frame where the tank is bolted on. I then turned on the key and with kill switch in "on" position, pressed the starter button. The engine turned over but no spark.



I disconnected the black wire with white stripe and still no spark.



I unplugged the yellow wire and tested for voltage, placing the red lead at the yellow connector (coming from CDI) and the black lead at battery negative. When I cranked the engine the volt meter read 7 or 8 volts before going down. Same for the pink connector.



I tested the blue and white wires coming from the engine to the CDI by unplugging the connector and testing the half coming from the engine. With engine rolling the voltmeter read about 2.4 volts.



Bad stator? That means removing the engine, no?



Hi,

I would be surprised if both of your coils are bad,,they could be but there are other things that are more likely. Faulty kill switch, CDI or stator come to mind.

How are you checking for spark? The valve covers are made of aluminum, when you test for spark hold the plug against the engine hangers or frame.



There is a black wire with a white stripe on it that comes from the kill switch and plugs into the CDI (black or gold colored box under the seat), try unplugging it at the bullet connector and test for spark again.



If you still have no spark I would try unplugging the yellow and pink wires coming into the coils from the CDI to see if there is voltage on them, there should be around 150 volts DC when rolling the engine over on the starter.

If you have no power there then you should check to see if there is power coming into the CDI from the stator. There is a plug with a blue and white wire that comes from the engine and plugs into the CDI under the seat. The blue wire should have approx 100 volts on it and the white should be 80 or 90 volts when rolling the engine over on the starter.

Try these tests and then let us know the results.
 

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I get my parts though my best bud lol My self
But please try your local Honda Dealer (I hope their friendly) If not drop me a line I, after that there is Bikebandit I guess.
 

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I would really recommend following the problem backwards from the spark plugs before you jump right into replacing parts and dropping the engine and opening it up. Start with the spark plug caps. See if there's resistance through the caps, if there's infinite resistance, the caps are bad and need to be replaced. Then see if voltage is getting through the coils by sticking one probe into the spark plug wire with the cap off and grounding the other one on the frame or negative battery terminal and turning it over and seeing if the needle jumps. At this point, don't worry about what the voltage is, as there's always the chance that you're reading the multimeter wrong or it's on the wrong setting. Just check to see if it's there. If you're not getting any voltage jumps through the spark plug wire, check to make sure the coils are properly grounded to the frame. It's unlikely even one coil will go bad, and both being bad at once is virtually unheard of, but check 'em to see if they're cracked. Once you're sure everything from the spark plugs back to the CDI is working properly, then you should start looking for a spare CDI to swap out, or think about upgrading the ignition system to the one the GL's use. If you have to replace the stator, then you might as well do the upgrade.



Sometimes troubleshooting your bike is like self-diagnosing an illness. We tend to think it's the worst possible thing it could be, smallpox instead of influenza, a bad stator instead of bad spark plug caps, you get the point. You really don't want to do hours worth of disassembly, spend hundreds of dollars on new parts, get it all put back together to find it still doesn't work, when the real problem could be fixed with 15 minutes of sanding or a couple of bucks spent on brass rods.
 

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I used a set of solid core Accel auto wires with built on straight plug caps as a test when I thought my plug wires were bad. They came from Advanced Auto parts and were a set for a V-8. What I found is the plug wires were not my problem. At any rate this was a fast easy test and as I did not get the wires dirty or damage them in any way so I plan to take them back for a refund.
 

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It is looking like a bad stator.



There are tests that you can do to narrow it down a bit more though.

There is another plug under the seat that has 3 yellow wires that come from the stator and plug into the regulator/rectifier. These are the wires that come from the charging windings on the stator,,if there is a short in any of these wires they will cause the symptoms you have.



A quick test for this is to try unplugging this plug and then seeing if the bike has spark at the plugs when you turn it over with the starter with it unplugged.(be sure to re-connect all the other wires you unplugged first)

If this makes no difference then you can check the resistance on the blue and white wires to confirm if there is a problem in the ignition windings on the stator.



This page at Shep's site has the proper resistance readings

http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=8&t=298



You do have to remove the engine to change the stator,,but if the problem with yours turns out to be in the ignition windings and not the charging windings you can fix the problem without removing the engine.



Let us know what you find out before trying to remove the engine or buying any new parts.



I used a set of solid core Accel auto wires with built on straight plug caps as a test when I thought my plug wires were bad. They came from Advanced Auto parts and were a set for a V-8. What I found is the plug wires were not my problem. At any rate this was a fast easy test and as I did not get the wires dirty or damage them in any way so I plan to take them back for a refund.
You cannot change the wires on a CX,, that is a luxury you GL owners have that the CX guys don't.
 

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Discussion Starter · #14 ·
Finally, some tests that are coming up within parameters:



white to blue -- 72

green to white -- 418

orange to green -- 108

light blue to green -- 108

orange/red to green -- 87

light blue/red to green -- 90



So does this mean the stator is good?



Also, could I do a continuity test from the inside of the spark cable to the yellow or pink wire depending on which coil I try? I tried it and I get no continuity. The insides of the spark cable where it clamps onto the spark plug look really clean.





It is looking like a bad stator.



There are tests that you can do to narrow it down a bit more though.

There is another plug under the seat that has 3 yellow wires that come from the stator and plug into the regulator/rectifier. These are the wires that come from the charging windings on the stator,,if there is a short in any of these wires they will cause the symptoms you have.



A quick test for this is to try unplugging this plug and then seeing if the bike has spark at the plugs when you turn it over with the starter with it unplugged.(be sure to re-connect all the other wires you unplugged first)

If this makes no difference then you can check the resistance on the blue and white wires to confirm if there is a problem in the ignition windings on the stator.



This page at Shep's site has the proper resistance readings

http://globalcxglvtwins.hostingdelivered.com/viewtopic.php?f=8&t=298



You do have to remove the engine to change the stator,,but if the problem with yours turns out to be in the ignition windings and not the charging windings you can fix the problem without removing the engine.



Let us know what you find out before trying to remove the engine or buying any new parts.





You cannot change the wires on a CX,, that is a luxury you GL owners have that the CX guys don't.
 

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The valve covers are made of aluminum



With about 1/10" of clear coat on them.




They are also insulated by the gasket and the rubber bolt inserts. The problem is not that they are aluminum, they are just not grounded to the rest of the motor!
 

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Also, could I do a continuity test from the inside of the spark cable to the yellow or pink wire depending on which coil I try? I tried it and I get no continuity. The insides of the spark cable where it clamps onto the spark plug look really clean.




Nope. See, your coils are essentially little transformers that take the relatively high current/low voltage from the pink and yellow wires and transforms it into relatively low current/high voltage needed to jump a spark across the spark plug gap. Transformers work through magnetic induction. It's all a bit complicated to explain, but essentially, inside your coils are two overlapping coils of wire that don't touch. The inside coil gets its current from the pink or yellow wire and is then grounded to the frame of the bike. As current flows through this inside coil to the ground, it creates a magnetic field that in turn creates a new potential in the outside coil. This potential in the outside coil builds up and is translated down the spark plug wire until the voltage is high enough to jump across the spark plug gap and be grounded to the heads of the engine. There isn't a direct connection between the pink or yellow wires and their respective spark plugs. Your multimeter measures resistance by creating a current between the probes and measuring the changes in that current as it flows through whatever it is you're testing. But it takes a great deal more current flowing through the inner coil to induce a current in the outer coil than a multimeter can supply.





Since you've run your rests on the stator and things seem copacetic there, I'm more convinced than ever that your coils are improperly grounded to the frame. It could still be the CDI, however, but since you've got your multimeter out, you might as well test the coils. Turn your multimeter to Rx1000. Stick one end of the probe into the pink or yellow wire (first one, then the other) where it plugs together under the seat. If you unplug it, make sure your probe is touching the part of the wire that leads to the coils, not the CDI. Touch the other probe to the negative battery terminal. Watch to see if the needle jumps. If it doesn't, I'd bet my favorite hat your coils are improperly grounded.
 

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I'm going to have to agree on this, even with a CDI system it takes a good connection to put a good primary pulse into the coils.
 

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All good advice above. Also, Scott, check the Quick Reference section in General Discussion. There are several spots that give supply sources.



I've used Discount Honda, and we get an extra amount off by mentioning this forum. Can't say I have had to replace the things you are mentioning in this thread so far, as my bike is an 82, but all the sources listed can at one point or another get you where you need to be at any given time. Some items are just going to be a luck of draw upon the membership here or on the other affiliated boards, such as the Aussie one and Shep's.



Have faith though. You, as most of us have at some point, found SOME WAY to get what we needed. Good luck to you, you have a bunch of really great people here to guide you along!!!!



Joel in the Couve.
 

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Discussion Starter · #19 ·
Here's a video of the test. I don't have an analog ohm meter, so please tell me what the results mean.



http://www.youtube.com/watch?v=zRLPAnbHF24



Thanks so much for your help!









Nope. See, your coils are essentially little transformers that take the relatively high current/low voltage from the pink and yellow wires and transforms it into relatively low current/high voltage needed to jump a spark across the spark plug gap. Transformers work through magnetic induction. It's all a bit complicated to explain, but essentially, inside your coils are two overlapping coils of wire that don't touch. The inside coil gets its current from the pink or yellow wire and is then grounded to the frame of the bike. As current flows through this inside coil to the ground, it creates a magnetic field that in turn creates a new potential in the outside coil. This potential in the outside coil builds up and is translated down the spark plug wire until the voltage is high enough to jump across the spark plug gap and be grounded to the heads of the engine. There isn't a direct connection between the pink or yellow wires and their respective spark plugs. Your multimeter measures resistance by creating a current between the probes and measuring the changes in that current as it flows through whatever it is you're testing. But it takes a great deal more current flowing through the inner coil to induce a current in the outer coil than a multimeter can supply.





Since you've run your rests on the stator and things seem copacetic there, I'm more convinced than ever that your coils are improperly grounded to the frame. It could still be the CDI, however, but since you've got your multimeter out, you might as well test the coils. Turn your multimeter to Rx1000. Stick one end of the probe into the pink or yellow wire (first one, then the other) where it plugs together under the seat. If you unplug it, make sure your probe is touching the part of the wire that leads to the coils, not the CDI. Touch the other probe to the negative battery terminal. Watch to see if the needle jumps. If it doesn't, I'd bet my favorite hat your coils are improperly grounded.
 

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Re-reading my post above I realized that I should have mentioned that when you were testing the blue and white wires from the stator, your meter should have been set to measure AC, not DC.

You never said if you tried unplugging the yellow wires or not, if you did and it made no difference then your stator may be ok.

I was not able to view the video you posted,,
 
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