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Discussion Starter #1
Has now after renovation started up the bike.
When driving, it misfires in the right exhaust pipe.
The carburetors are cleaned and all gaskets are replaced.
Valves are adjusted.

Do you good people in the forum have any thoughts about that?
 

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Thomas it might help if you reminded us about the history of your bike, the model it is and the problems it has and the steps taken to correct them. I checked your thread on the mechanical seal and see that your bike is an '81.
How is the misfire in the right exhaust pipe evident? Do you hear the misfire? Perhaps a pop from the right exhaust pipe? Remember that if you have the stock exhaust system the exhaust gases from the left and right cylinders mix in the H-box.
A usual cause of popping in the exhaust is an exhaust leak. If on over-run it may indicate a problem with the ACVs (air control valves )
 

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Discussion Starter #3
Thomas it might help if you reminded us about the history of your bike, the model it is and the problems it has and the steps taken to correct them. I checked your thread on the mechanical seal and see that your bike is an '81.
How is the misfire in the right exhaust pipe evident? Do you hear the misfire? Perhaps a pop from the right exhaust pipe? Remember that if you have the stock exhaust system the exhaust gases from the left and right cylinders mix in the H-box.
A usual cause of popping in the exhaust is an exhaust leak. If on over-run it may indicate a problem with the ACVs (air control valves )
Supermoderator...sounds big.

CX 500 C, -81, 56000 km, blue. Everything is original on the bike.

Hear the missfire,pop from right exhaust pipe, occurs when the gas is released from a higher engine speed. Around 4-5000 rpm and higher.

No damage to the pipes or H box as far as I can see.

Carburetors is clean, new gaskets and acv also change in booth carb.

Valves are adjusted. Carb is not synchronized yet, still waiting for the tool.

The damper on the left carburettor does not close properly, must be assisted to the initial position with the throttle handle.
 

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Discussion Starter #5
Vac leak of perforated {or jammed} ACV most likely.
How to solve it?
As I said, there are two new acv in the carburettor.
Can they get stuck or go sluggishly?
Should it be oiled with something during installation?
 

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No oil. It attacks rubber. You'd likely know if they were sticky from the installation I guess. If the brass knob slid into the carb body OK they're likely not sticky. If new they're also not perforated.

But I fit some ebay ACVs to one of my CXs and they actually made it run quite badly. If you still have the originals you could refit them to see if there's a difference. While not ideal small holes in the rubber can be fixed for the test..

What was the source of the AVCs?

How were the O rings between intake runner and head?

Have you checked the runners themselves for splits in the rubber?
 

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Discussion Starter #7
No oil. It attacks rubber. You'd likely know if they were sticky from the installation I guess. If the brass knob slid into the carb body OK they're likely not sticky. If new they're also not perforated.

But I fit some ebay ACVs to one of my CXs and they actually made it run quite badly. If you still have the originals you could refit them to see if there's a difference. While not ideal small holes in the rubber can be fixed for the test..

What was the source of the AVCs?

How were the O rings between intake runner and head?

Have you checked the runners themselves for splits in the rubber?

Avc Honda original.

Do you mean the rings between the intake and the cylinder, brand new.

The runners, is it the intake rubber you mean.?

Intake manifold brand new, not original.
 

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Discussion Starter #9
That's those ruled out.

May just be bad synch. That'll cause popping in itself
it is possible that the synchronization is poor even if you make a basic setting before mounting.

The screw is unscrewed two turns on each carburetor
 

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Discussion Starter #10
That's those ruled out.

May just be bad synch. That'll cause popping in itself

Can the carburetors become very unsynchronized if you basically set both screws with two turns from the bottom?
 

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Those two screws set the mixture (mostly at idle), which can have some effect on carb balance, but synchronization of carbs is primarily done with the screw adjustment located in the rotating linkage between the carbs, there is a lock nut on this screw to keep it from changing. This adjustment changes the alignment of the two throttle butterflys to eachother, and causes them to both pull equal vacuum and produce equal rpms. Which is called synchronized. Among other advabtages to having closely synchronized carbs is more overall engine power, better fuel economy and smoother engine running.
 

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Discussion Starter #12
Those two screws set the mixture (mostly at idle), which can have some effect on carb balance, but synchronization of carbs is primarily done with the screw adjustment located in the rotating linkage between the carbs, there is a lock nut on this screw to keep it from changing. This adjustment changes the alignment of the two throttle butterflys to eachother, and causes them to both pull equal vacuum and produce equal rpms. Which is called synchronized. Among other advabtages to having closely synchronized carbs is more overall engine power, better fuel economy and smoother engine running.
Thanks, good info!
 

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2 turns out is just the starting point for those screws. Once you have the engine running they need to be fine tuned by turning them in or out slightly while listening for the engine's RPM to increase (adjust one carb's screw, re-adjust the idle RPM, adjust the other carb's screw and then set the idle RPM again).
Adjusting the mixture screws and synchronizing the carbs (also called "balancing") should be performed any time they have been disassembled for cleaning.
Note that you will need some sort of vacuum gauges to balance the carbs.

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

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 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. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel because old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet. If your bike still has the original rubber brake line(s) (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).
 

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Discussion Starter #14
Has now synced the carburetors. It still misfires and sometimes "cuts" as it seems the ignition.
Must have help because now all my ideas are gone.
Basically changed everything except the Cdi box.
Grateful if anyone can tip about something I missed
 

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Discussion Starter #15
Please, someone must have a theory about the problem ...
 

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Discussion Starter #17
Brand new, black.
However, the ignition coils are probably since -81
 
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