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Discussion Starter · #1 ·
I have this 1981 cx500 that I am working on and it has been sitting since '87. So I cleaned the carburetor fixed the starter put in fork seals got it started and coolant was leaking out the weep hole. New w/p seal. Now It starts and idles and runs good on the low end but when revved it starts popping. Cleaned the carbs again and again then realized that maybe it is the ignition. So I did the ohm test.

1/5 113 ohms

2/5 96 ohms

3/5 no reading

4/5 110 ohms

6/5 95 ohms

7/5 200 ohms

8/9 83 ohms

5/9 299 ohms



Looks like 3/5 and 5/9 are out of specs. What should be my next step? It is charging @ 14.5 volts.

Thanks.
 

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check that 3/5 reading again - make sure you have good contacts - maybe that wire is frayed somewhere near the engine case - odd to see a pulser coil fail.. then the low speed coil has less resistance..



I think the carbs might still have some cleaning to go - I would try that first if I wasn't in any hurry.

Hate to pull the motor if it was just a carb plugged jet.

when you say it revs cleanly - how far will it rev into the range - and where does it start to pop?

when riding or under load, does it struggle to gain reves?

Or it could also be a vacuum leak around the sealing areas of the carb rubbers - inlet & outlet??
 

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This is a very curious post, since you only joined a few hours ago. Could you fill out your profile a bit with your location and add the bike model and year to your signature to help us in the future?



You seem to have read up a bit on the tests, and the symptoms cover many factors. What is the mileage on the bike?

The water pump seal may fix itself after running, but the other things are more a concern.



Help us out with more detail.
 

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Discussion Starter · #4 ·
It is a 1981 cx500 custom has 18000 miles. I took off the pulsar coil cover to check the wires. The wire from the connector to the coil is fine so I checked the wire directly at the coil and no reading.It revs to about 5 or 6000 rpm before starting to pop but it will get up to 65 mph or more. It is worse under load than if I'm just revving it. I did check for vacuum leaks.I have been on this forum many times searching for answers but decided to join so I can post.

It has been very helpful.



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Hmmmm... a CDI bike hitting the wall in the 5000 RPM range.... are you fellers thinking what I'm thinking?



First off though, try new plugs and check the resistors in the plug caps.
 

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Discussion Starter · #7 ·
I did take apart the plug caps and removed resistors and have zero resistance on them. I will check the spark plugs and coils. Are the off numbers on my advance pulsar and low speed source coil a concern?



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On the laptop so havent got the diagram

but IIRC 3 and 7 are the advance coils

and 3 being open circuit means one set has failed



This in itself isnt the typical stator failure

but 5-8 is low, so it may be Ignitech time.



the 14.5V volt reading is good but thats the charging side

and only partially related to the ignition side
 

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I'm really not sure about the WWF as I never had to do it myself

I have heard of some using it and tried it once on a good working bike out of

curiosity but couldnt get it to rev very well.



I do know forward voltage on the white wire is blocked by a diode in the CDI box

so putting it on the blue wire connector may give some power

to the CDI when the blue wire windings have failed.



Try it and see I suppose.
 

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Discussion Starter · #11 ·
I pulled out the spark plugs and the left one had some carbon, not bad maybe a little rich. The right looked lighter but it was also a bit damp. I changed the plugs but it ran the same, crappy.
 

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Maybe then the problem is the dud advance coil. It might be happy to run until there isn't enough advance on the cylinder with the dud advancer coil at higher RPM..



The advance function can be checked with a timing light.



I bet it's the left cyl. with the dud. Late ignition timing may mean it is not getting the chance to complete it's combustion cycle, hence the dark plug.

Whether or not this is your actual problem it needs to be addressed before much further diagnoses can be reallistically made.



EDIT. This post has been edited to read less like gibberish.
 

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Discussion Starter · #13 ·
What is the procedure to check the advance pulsar coil with a timing light? Also can the advance coil be removed with the engine in. If it is the advance coil would I be better off getting an ignitech?



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First of all remove the timing inspection and front crank caps. To orient yourself with the marks you'll be looking at

rotate the crankshaft clockwise until you find the timing marks for, say, the left cylinder. You are looking for the LF , and LT marks proceeded by 2 undesignated marks. These last 2 are your full advance marks.



With the motor idling and the timing light aimed through the timing inspection hole {TIH}you should see the LF mark lined up with the datum pointer on the pulser inside the TIH.



Slowly increasing the RPM should see the timing marks beginning to advance at around 1,750 to 2,250 RPM and reach the 2 plain marks by 5,500 to 6,000 RPM. if the advancer coil for this side is functioning correctly.



Repeat for the right side using the RF and RT marks.



Any readings out of the norm indicate a failed component as these ignition systems are not adjustable. And if this test reflects the resistance tests you have already done you can expect one side or the other to be out of spec.. I'm expecting it will be the left one.



The link to the factory manual is at the bottom of any of Blindstitches posts so give the relevent section there a read through too.



EDIT, looking at the manual, the 3 to 5 pin test is in fact the left advance pulser..... And yes, while it's pretty fiddly, the advance pulsers can be replaced with the engine in. You may need a small mirror to check for proper alignment.
 

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Discussion Starter · #15 ·
I finally had a minute to check the timing. The left cylinder was advancing fine but the right didn't even budge.

Is this definitely the advance pulser coil or is there a chance that it is some other component? Like the CDI box?



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At this point I'll defer to somebody with more experience of CDI systems to try to answer your question since the cylinder I was expecting to not be advancing is the one that is.



The left cylinder is the one on your left when you are sitting on the bike, right?



If you haven't made this fundamental error I would tend to wonder if the wires to the 2 advancer coils have perhaps been reversed at some point. Do the colours for these match up where they go through the 8 pin connector?



My diagram here shows the 3 to 5 pin test as the left cylinder advancer coil.and the 7 to 5 as being the right.



Left wire - LB/W



Right wire - O/W
 
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