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1981 CX500C
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Discussion Starter · #1 ·
Hello all!

I just got this 81 cx500c.
It had not been started in 7 years.
Things I've done so far:
Drained old fuel.
Oil& filter change.
Removed and rebuilt the carburetor..
It does idle at 1100 rpms.
When it started I felt like it sounded like there was a knocking noise.

Today I went up and down my street.
Came back, the left side exhaust pipe looked like attached photo. Right side no change!
I'm sending it to the shop for new tires. I'm just I guess asking if anyone knows the reason. So when I ask them to look into it, I don't sound like a noob. Everything Everything internal engine is foreign to me.

Also if it means means anything the left side of carb was way worse than the right side.
209061
 

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It is probable that the left side header is a single wall non-OEM. It is normal for them to blue when heated. If the right side did not blue it could mean that the right side is not firing or the right side header is a double wall OEM header. A simple test would be to start the engine then remove the right side high tension cable. If nothing changes it means that the right side is not firing,
 
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'84 CX650E that is evolving into a GL500
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I think you mean that if you unplug the right spark plug cap and nothing changes the right side isn't firing.

What do you mean by "Removed and rebuilt the carburetor "?
Which kit did you use? (some include metal parts that are substandard and/or incorrect and the original hard parts seldom need replacing so we recommend using them instead of any that come in the kit)
Did you remove all of the jets and the emulsion tubes? (if not you only did half the job at best)
Did you adjust the air screws and balance the carbs after you re-installed them? (that part is as important as the cleaning)

BTW: Welcome to the forum. Please add your location and your bike's model and model year to your profile so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. If you are replacing the tires I don't need to tell you to check their date codes on and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet) but I will recommend making sure the shop put them on with the rotation direction arrows pointing the right way before you ride it home (we've had a few reports of that happening).
If your bike still has the original rubber brake line (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
 

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1981 CX500C
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Discussion Starter · #4 ·
I think you mean that if you unplug the right spark plug cap and nothing changes the right side isn't firing.

What do you mean by "Removed and rebuilt the carburetor "?
Which kit did you use? (some include metal parts that are substandard and/or incorrect and the original hard parts seldom need replacing so we recommend using them instead of any that come in the kit)
Did you remove all of the jets and the emulsion tubes? (if not you only did half the job at best)
Did you adjust the air screws and balance the carbs after you re-installed them? (that part is as important as the cleaning)

BTW: Welcome to the forum. Please add your location and your bike's model and model year to your profile so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. If you are replacing the tires I don't need to tell you to check their date codes on and replace them if they are over 5 years old no matter how good they look & feel (old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet) but I will recommend making sure the shop put them on with the rotation direction arrows pointing the right way before you ride it home (we've had a few reports of that happening).
If your bike still has the original rubber brake line (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid). And don't forget things like the rad hoses and the boot between the engine and swingarm (they can crack on the bottom where you don't see it).
Hiya! Thanks for the info and feedback!

Okay, I believe I have now correctly updated!

Okay, I did get new plugs and gapped to recommended .6. Here is what the old ones looked like and the the purchased one look like. Maybe the difference means something. Bought before I removed the older ones. 🤦‍♀️ They store told me I should purchase a performance plug. My logic ... it's a cruiser...

I watched a video of older gent with a go pro. Tried to read as much as possible about the specs. But yeah, completely unassembled everything that could be taken apart. Measured the screws with micrometer to be sure they matched. .005 difference between the two.
Reset all to zero. Bottom two adjusters all the way to the right then 2.5 turns on each side. "Throttle screw" I returned to neutral and then adjusted to bring rpm up to proper rpm (from what I've learned is correct rpm).
Carburetor here is the link of what it looked like, I have also posted a few more videos of the journey! As far as parts used I ordered kit from a random local shop. I pulled all of it apart and inspected everything. It was really really bad!
1981 Honda CX500C Part 3 carburetor

209088
 

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'84 CX650E that is evolving into a GL500
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YouTube can be a great source of information but it can also be just as great a source of misinformation so without knowing which video you watched I can't comment on whether the "older gent with a go pro" had any idea of how to correctly adjust them but I'd say if he didn't use vacuum gauges probably not.
The Factory Shop Manual or resources recommended by experienced members of this forum should always be your primary sources if information.

2.5 turns out is only the starting point for adjusting the screws and once they are adjusted you need to balance the carbs (you will need vacuum gauges for that).
Speaking of resources recommended by experienced forum members, your video sounds like you don't know much about carbs (what you called the "cap" os the float bowl - the cap is on the top of the carb) so I strongly recommend getting need Larry's Carb Book before you go any farther (Larry is also known as LRCXed on the forum)

Re plugs: A few use the iridium plugs but most of us just use the stock type like your old NGK D8EA plugs. They usually come from the factory with the correct 0.6 to 0/7mm gap (I usually check them before installation but I don't remember ever needing to adjust one).
BTW: Even if I knew they were working perfectly I would recommend replacing those old plugs before the rust works its way into the threads (I had to replace a head on my GoldWing because I didn't change the plugs soon enough).
 

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Removed and rebuilt the carburetor
I'm curious what you mean by this? A thorough cleaning/rebuild of the carbs is a pretty involved process so just curious what you did. The reason i say this is there have been many post on this forum about carbs being rebuilt but after further investigation it wasn't really done properly. Don't get me wrong, not knocking anyone's abilities about carb cleaning but it's detailed enough that one of the senior forum members actually wrote a book about it.

CX500/Gl500 Carb book (donlhamon.com)
 

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1981 CX500C
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Discussion Starter · #7 ·
Respectfully, it is Steve Harley. Watching this actually gave me the courage to take a crack at it. I've watched many a video so far, read many things. Lost in very old discussion groups. But here I am, no I do not know very much about the carburetor or official terminologies YET but progressively learning. I honestly would repeat the carburetor process as many times as needed to get it right! I soaked and cleaned with gas and thinner. I also went out and gathered some fishing line, to be sure! :)
Gasket kit I will find which I purchased, it was pricey (NOT Amazon for $18.99 USD)
Always learning. I know cars, I am self taught, just not old enough for the carburetors. The best video I had come across:
1981 Honda CX500C Part 3 carburetor

Thank you for the link to the book, I have made the immediate purchase! I don't think I'll be letting this Honda go in my lifetime, soo here I am. Piggy backing and sponging information as my issues arise.

Reason I am here, to get lost in the rabbit hole of posts before my arrival and simply not wanting to mess this bike up in the process. :)

My videos maybe be cringeworthy to most whom are the professionals! I appreciate the feedback and i am taking notes! Here's my last one for the day.

Here's my official sound of a running honda, that didn't have life not too long ago. Only can get better, right?!


Particular meme comes to mind:
209089
 

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'84 CX650E that is evolving into a GL500
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You'll get the hang of everything soon enough. Most of us were young and new to bikes once and some of us still remember what that was like.

Your videos aren't terrible. At least you actually show what you are trying to show.

BTW: Anyone who has ever had a bike with a kick start can appreciate that meme ;-)
 

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I think you mean that if you unplug the right spark plug cap and nothing changes the right side isn't firing.
Thanks Bob, corrected my post.
 
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