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Discussion Starter · #1 ·
Hello CX500 forumers,

I recently did a quick clean of the carbs on my 78 CX to try and nurture this problem of the bike not starting or even sputtering when turning over but it will start easily when I push start it in gear. It runs better now but the problem still persists. Is there facet of the carb that deals directly with starting that could be unhappy? I've not a lot of carb experience but am comfortable tearing most things apart.

Thanks for any wise words and advice.
 

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it sounds like your starter is not spinning it over fast enough how does it sound?? while cranking if you are not sure can you post a sound clip of it spinning

do a voltage test at the starter while it is cranking
 

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Discussion Starter · #3 ·

Here's a link to the video. I've run a trickle charge so the battery is as charged as it will get, not to say that the battery is still prime though.
 

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the starter is spinning it over fine

ok now find the 3 yellow wires and the white connector on the back inner fender under the seat and unplug them then see if it starts

if it does not then undo the black with white tracer wire that comes from the cdi box and goes forward with the pink and yellow

take note that if the bike starts you will not be able to shut it off till you stall it or plug the black with white back in

let us know what you find
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Is this bike using a stock CDI unit, or the Ignitech replacement? What battery voltage do you read while cranking?

The only reason I can imagine that it would bumpstart, but not with the starter is if the starter is drawing enough current that the battery is dropping below the Ignitech's voltage threshold. I don't know if the stock CDI has such a threshold.


R
 

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This has happened a few times now.

If it starts with the starter when the 3 yellows are unplugged, one of the charging coils on the stator most likely has a short to ground.
 

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Would the extra load of the starter on the charging circuit induce a lower output from the ignition side? (Just trying to understand how the fault happens.)


R
 

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Would the extra load of the starter on the charging circuit induce a lower output from the ignition side? (Just trying to understand how the fault happens.)


R
When you figure it out,,let me know, I don't know why it happens either.:)

When I got my first CX, it had no, or very weak spark. Just by fluke I found that unplugging the 3 yellow wires solved the weak spark issue. I never tried push starting it, but judging by what I have seen on this forum, it may have started with a push, but I can't understand why a short in the charging system causes no ignition.

I imagine it will continue to deteriorate until the bike will not start at all, push or not.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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I would guess that the shorted circuit is inducing a field that suppresses the neighboring circuit. But that's all I can do -- guess.


R
 

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Discussion Starter · #10 ·
Hey guys,

I tried the wire unplugging recommendations with no avail. Any other ideas or steps to lead to a diagnosis?

I really appreciate all the input
 

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Try doing the stator resistance tests.

 

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Try doing the stator resistance tests.

+ when you´re already in there - measure voltage (AC) between 8 and ground (5) and also 9 and ground while cranking it. You should see something like 85 V on one and slightly more on the other one, If memory serves. I´ve forgotten which of them should read highest.

/Sture
 

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Discussion Starter · #13 ·
Alright I was toying with some other things on the bike and I tried starting it with said wires unplugged and I finally got it to start. It is only with the black wire with white stripe disconnected, what does this reveal?


Sent from my iPhone using Tapatalk
 

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I think it means you have a bad kill switch (but I'll leave it to the gurus to second that).
Basically, by unplugging to black/white wire you bypass that switch.
Blivy
 

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yep mine was doing that.. took it apart and fixed it this morning.
 

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Hello Sorry if I write wrong.
The fact that I live in Ukraine. I very badly understand English. I have the same problem with the Honda CX500. Starter will not start. Checking the generator coil on the top chart correctly found that all except - 5/9-180-184.....
Whether because of this engine starts only tug (pushing the bike)?
 
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