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Discussion Starter · #1 ·
Pretty soon everything on this bike will be new and serviced because i have worked on it way to much. My problem is, after the bike warms up to operating temp, it will miss erratically when i give it about 1/3 throttle or try to accelerate quickly. I have to accelerate slowly or it will bog down and miss. When it is cold it is snappy and runs great. Does that sound like a possible coil failure? The carbs are rebuilt, float level set, copper rod in the plug caps, in line fuel filter.

1979 CX500c
 

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It could be a coil,,but may also be a CDI problem.



I would try removing plug wires while riding it. When it is bogging reach down and lift the plug wire off one side,,if it makes no difference, the problem is on that side.

If the bike dies, that side is working.



Once you figure out which side is not working,,try swapping the coils from one side to the other,,if the symptom follows the coil,,that coil is probably bad.



If it makes no difference then it is probably CDI,,could be stator too.

Try the coil swap and let us know what you find out.
 

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Discussion Starter · #3 ·
It could be a coil,,but may also be a CDI problem.



I would try removing plug wires while riding it. When it is bogging reach down and lift the plug wire off one side,,if it makes no difference, the problem is on that side.

If the bike dies, that side is working.



Once you figure out which side is not working,,try swapping the coils from one side to the other,,if the symptom follows the coil,,that coil is probably bad.



If it makes no difference then it is probably CDI,,could be stator too.

Try the coil swap and let us know what you find out.
 

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Discussion Starter · #5 ·
Tried what you said and it stayed running aside from that cylinder quit firing when i pulled the plug. Soooo....does that mean the CDI? Should I check the Ohms reading on some things?
 

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Tried what you said and it stayed running aside from that cylinder quit firing when i pulled the plug. Soooo....does that mean the CDI? Should I check the Ohms reading on some things?


Once when I had a CDI go bad, it acted much the way you describe.

What I did to figure out if it was a CDI or coil was drive it until it warmed up and would bog down when I gave it wide open throttle. when I opened the throttle wide open the bike would bog and stay bogged down,,when it was bogging and I had the throttle still wide open I reached down and removed the left plug wire, when I did this the bike died so I stuck the wire back on. Then I drove the bike and cranked the throttle again and caused it to bog,,again while it was bogging down and I was holding the throttle wide open I used my left hand to remove the plug wire from the right side,,this time it made no difference at all. This told me the problem was the right side not firing.



I then changed the coils from one side to the other but the symptom never changed,,I tried removing the wires again using the above procedure and it was still the right side not working, so I knew it was not a coil problem.



Is the above procedure the same way that you removed the wires? If the bike was not bogged down when you removed the wire it would not be an accurate way to test it.



I had a spare CDI so I was able to change it and that solved the problem. If you do not have a spare then I would suggest you try doing the resistance tests on the stator,,if it checks out ok you can probably assume it is a CDI problem.



I never mentioned that it could even be as simple as a bad spark plug,,it would not hurt to try new plugs before doing any thing else.
 

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So when you removed the plug wires from each side the bike did not completely die but it did make a difference in the engine?



If this is the case it would seem that it mat not be a problem on one side only.



I would do the stator resistance checks when the engine is warm, take the bike for a drive and when it is working bad pull the seat off and test the wires that come off the stator.



 

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I think you would use the 2k setting.
 

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Discussion Starter · #11 ·
With the multimeter set to 2k ohms

Heres my numbers cold

1-124

2-104

3-229

4-124

6-101

7-222

8/9-91

5/9-362



Heres my numbers hot

1-138

2-119

3-271

4-143

6-114

7-265

8/9-108

5/9-264
 

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The 5/9 reading is borderline when the bike is cold but is really low when it is hot.

You could try removing the spark plugs,,unplug the blue and white wire plug and test for AC voltage on those wires when turning the engine over with the starter.

Set your meter to read 150 or so AC volts. Place the positive lead on the blue wire(#8) spade and the negative lead on the negative post of the battery,,when the engine is turning you should see 80-100 volts on the blue wire.

Then test the white wire(#9) the same way,,it should be 70-90 volts.
 

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if that 5-9 hot figure is correct then I'd say the stator

is on the way out.

Time for a new one or better still, an Ignitech methinks
 

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Discussion Starter · #15 ·
The 5/9 reading is borderline when the bike is cold but is really low when it is hot.

You could try removing the spark plugs,,unplug the blue and white wire plug and test for AC voltage on those wires when turning the engine over with the starter.

Set your meter to read 150 or so AC volts. Place the positive lead on the blue wire(#8) spade and the negative lead on the negative post of the battery,,when the engine is turning you should see 80-100 volts on the blue wire.

Then test the white wire(#9) the same way,,it should be 70-90 volts.






I got 106v-Blue wire

87v-white wire
 

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Is it safe to assume that it is the stator then?


Unfortunately it looks like it.Depending on your finances you may want to upgrade the ignition system to an Ignitech unit with the better G8 stators.Use the search function for Ignitech.What you lose on the cost of the Ignitech you get back a bit on the lower cost of the G8 stators.In effect you give the bike a 21st century upgrade but remember that the Ignitech units rely more on the battery so keep batteries fully charged and topped up and in good state if you choose to go this way.
 

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Yes , it looks like your stator is bad. The voltage numbers you got are ok but it is a "no load" test,,if the numbers had been low it would have helped confirm that your problem is the stator,,high numbers don't prove it is good though.



You can buy an Ignitech and use it with the stator you have in the bike now, you would not need to install a G8 stator, as long as your bike is charging the battery alright. In the future if you have ever have a problem with the charging system you can replace the stator with the cheaper yet more powerful G8 stator that does not have any ignition windings on it.
 

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Discussion Starter · #19 ·
Well, I'll either look into getting the ignitech or another stator. I'm balls deep in this CX project and can't back out now. If i ever at least want to sell it that will have to be fixed first anyways.
 
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