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Discussion Starter · #1 ·
Hi!

I recently bought a Honda CX500C, 1981, and I have been working on getting it started. After fixing the starter clutch, the bike ran fine, and I have been taking it for a few rides lately. But during the last 2 rides, I started noticing pops from the exhaust while rolling, holding in the clutch and in neutral. At first it only happened when the engine was warm, but now it happens whenever I start the engine. Is there any way for a guy with very little experience to figure out what can cause these issues, and maybe even how I can fix this myself? Is it the carburator, or do I have other/bigger issues?

Video of the bike + sounds (The engine here is cold, and has been running for less then a minute. Hopefully the pops can be heard properly)

Thanks in advance!
 

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I'd say air/fuel mixture... running rich?
Can you start the bike cold without choke? If so running rich.

Could be an airleak at the exhaust-junctions/header.??...especially if happened "suddenly"...

Does it (the popping) go away after you ride it?...if so exhaust joint likely

Edit: Both of these would be fairly simple to check.....
I have left out other possibilities such as "exhaust valves" not seating etc......
 

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Discussion Starter · #3 ·
I'd say air/fuel mixture... running rich?
Can you start the bike cold without choke? If so running rich.

Could be an airleak at the exhaust-junctions/header.??...especially if happened "suddenly"...

Does it (the popping) go away after you ride it?...if so exhaust joint likely

Edit: Both of these would be fairly simple to check.....
I have left out other possibilities such as "exhaust valves" not seating etc......
The bike can not be started cold without using the choke. The popping also stays there during the entire ride, unfortunaly. I'll see if I can figure out regarding the exhaust-junctions/header. Thanks for the reply.
 

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tighten header to silencer clamp.....but im thinking more likely at the header gasket.
bike running lean can also cause some popping tho thats less often..
from a car website:
A "lean" mixture is one that doesn't have enough fuel, and too much air. Such a mixture could be caused by low fuel pressure due to a failing fuel pump, a clogged fuel filter or clogged fuel injectors. When a lean mixture combusts, it burns more slowly, meaning there will still be some air and fuel that isn't used up when the exhaust valves open -- leading to a backfire.
Obviously no injectors in this case but blocked jets in the carb.....
 

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Go easy on tightening the header pipe to head clamp bolts, they’re small and if they break it just adds another task to remove/replace them. I’d be thinking carb dirty idle jet.
 

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Discussion Starter · #6 ·
tighten header to silencer clamp.....but im thinking more likely at the header gasket.
bike running lean can also cause some popping tho thats less often..
from a car website:
A "lean" mixture is one that doesn't have enough fuel, and too much air. Such a mixture could be caused by low fuel pressure due to a failing fuel pump, a clogged fuel filter or clogged fuel injectors. When a lean mixture combusts, it burns more slowly, meaning there will still be some air and fuel that isn't used up when the exhaust valves open -- leading to a backfire.
Obviously no injectors in this case but blocked jets in the carb.....
I'll have a look at it, i'll keep you updated as well.
 

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Discussion Starter · #7 ·
Go easy on tightening the header pipe to head clamp bolts, they’re small and if they break it just adds another task to remove/replace them. I’d be thinking carb dirty idle jet.
I'll have a closer look, just to make sure they're not loose, won't be going to hard on them. Might need to go for another carb cleanup as you said.
 

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It’s got aftermarket air filters. Just out of interest, remove them, start the bike and see if popping changes, that’ll point to carbs; don’t ride without them.
I agree with all above.
The fact it just started doing it, something changed. But it could also be a change in float height, again a simple check.
A Guzzi I had started doing that. That was due to the points closing. Of course your bike doesn’t have points, but let’s not open the electrical can of worms; yet.
 

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For what is worth, about two weeks ago I had a popping issue on the right side... I took off the carbs, cleaned them and had to tap the slow idle pressed in jet to extract it. I then could clean the jet and the inside of the carb where the jet lives. After putting everything back I calibrated the carbs and retuned the air mixture. Check / replace your spark plug, check your plug wire and plug cap for breaks . Also do a compression test.... Regards
 
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My GL500 that sat for 14 years in my neighbor's garage popped during the second season and went away on its own. This is its third season, and every season it seems to run better. I didn't clean the carbs except with seafoam. Only adjusted the carbs, timing and carbs.
 

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Discussion Starter · #11 ·
Update (If anyone is interested): I removed the air filters as mentioned above, and checked to see if the popping changed, it did not. I left the bike running for about 2 minutes, to see if there were any changes to the sound, or how often it happens, nothing there as well. I did notice though that the popping only happens on the right exhaust, and that the exhaust on the right side also gets a lot warmer/faster warm than the left side, even just after 2 minutes.


It seems to be close to the same problem @Wyn64 mentioned above. So I'll take a closer look at the carbs, and have them properly cleaned to see if that helps. Thanks for the help everyone, greatly appreciated!
 

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Hi!

I recently bought a Honda CX500C, 1981, and I have been working on getting it started. After fixing the starter clutch, the bike ran fine, and I have been taking it for a few rides lately. But during the last 2 rides, I started noticing pops from the exhaust while rolling, holding in the clutch and in neutral. At first it only happened when the engine was warm, but now it happens whenever I start the engine. Is there any way for a guy with very little experience to figure out what can cause these issues, and maybe even how I can fix this myself? Is it the carburator, or do I have other/bigger issues?

Video of the bike + sounds (The engine here is cold, and has been running for less then a minute. Hopefully the pops can be heard properly)

Thanks in advance!
Your carb has a few tiny worm holes inside that may need to be cleaned out. That solved my popping.
 

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I should have thought, being pod filters, removing them wouldn't affect mixture virtually at all! Sorry my bad.

You could of course whilst they are off put your hand carefully over the carb inlets and see if it affects the popping by varying how much you restrict the air.

But as already mentioned, give the carbs a good seeing to, making sure you clean all jetways, as Tony says.

I'm pretty fastidious when I clean my carbs, but once had to do them three times! Different bike though.
 

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I should have thought, being pod filters, removing them wouldn't affect mixture virtually at all! Sorry my bad.

You could of course whilst they are off put your hand carefully over the carb inlets and see if it affects the popping by varying how much you restrict the air.

But as already mentioned, give the carbs a good seeing to, making sure you clean all jetways, as Tony says.

I'm pretty fastidious when I clean my carbs, but once had to do them three times! Different bike though.
Yes. There is a .008 of an inch worm hole that is most likely plugs. I had to file a 3 inch long paper clip down to size at the end to snake it through. Had to do it with both bikes.
 

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I should have thought, being pod filters, removing them wouldn't affect mixture virtually at all! Sorry my bad.

You could of course whilst they are off put your hand carefully over the carb inlets and see if it affects the popping by varying how much you restrict the air.

But as already mentioned, give the carbs a good seeing to, making sure you clean all jetways, as Tony says.

I'm pretty fastidious when I clean my carbs, but once had to do them three times! Different bike though.
I should have thought, being pod filters, removing them wouldn't affect mixture virtually at all! Sorry my bad.

You could of course whilst they are off put your hand carefully over the carb inlets and see if it affects the popping by varying how much you restrict the air.

But as already mentioned, give the carbs a good seeing to, making sure you clean all jetways, as Tony says.

I'm pretty fastidious when I clean my carbs, but once had to do them three times! Different bike though.
For what is worth, about two weeks ago I had a popping issue on the right side... I took off the carbs, cleaned them and had to tap the slow idle pressed in jet to extract it. I then could clean the jet and the inside of the carb where the jet lives. After putting everything back I calibrated the carbs and retuned the air mixture. Check / replace your spark plug, check your plug wire and plug cap for breaks . Also do a compression test.... Regards
Cx500 carb worm hole fix
 

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Discussion Starter · #16 ·
Thank you for the response as well as the video. I pulled the carbs of today, opened them and had a look, managed to get a paper clip to fit, assembled everything and put it back on the bike. Took it for a test ride and shortly after the popping started happening again. I might not have been able to clean the carbs out perfectly. Do you think having it ultrasonically cleaned would be the best option?
 

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Thank you for the response as well as the video. I pulled the carbs of today, opened them and had a look, managed to get a paper clip to fit, assembled everything and put it back on the bike. Took it for a test ride and shortly after the popping started happening again. I might not have been able to clean the carbs out perfectly. Do you think having it ultrasonically cleaned would be the best option?
I bought an ultra to clean mine. That would help. All those holes must be draining. Did you verify that that one hole is draining down from the middle tower.? On both carbs.
 

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Discussion Starter · #18 ·
I bought an ultra to clean mine. That would help. All those holes must be draining. Did you verify that that one hole is draining down from the middle tower.? On both carbs.
Not 100% sure, I would say about 90%. I do know someone with an ultrasonic cleaner though, so I'll get in touch with him and see what he can do for me. Thanks again!
 

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Not 100% sure, I would say about 90%. I do know someone with an ultrasonic cleaner though, so I'll get in touch with him and see what he can do for me. Thanks again!
When you fill up the tower you should see it drain down and out that small hole I pointed out. If the fluid does not drain down than it’s not cleared out. The the middle of the warm hole it snakes around inside. I used to have a picture of what it looks like. I can’t find it right now. So I file the paper clip and on a debuting bench wheel and measured with calipers till I reach the correct diameter for the hole.
 

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Not 100% sure, I would say about 90%. I do know someone with an ultrasonic cleaner though, so I'll get in touch with him and see what he can do for me. Thanks again!
209577

Found the photo that should help.
 
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