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1981 PC01 CX500 Custom
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57 Posts
Discussion Starter · #1 ·
I've just finished maintaining a carb for my current project.
Since the is constant rumours whether to close or not to close the vents to enable a better cold start, I found a cheap variant of caps which may be available in every household.

So if you want to give it a try just look at the pics.
Orange Wood Font Eyewear Material property


Bicycle handlebar Motor vehicle Automotive lighting Automotive tire Bicycle part
Orange Wood Font Eyewear Material property
Bicycle handlebar Motor vehicle Automotive lighting Automotive tire Bicycle part
 

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Premium Member
1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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12,243 Posts
You shouldn't...
 

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5,782 Posts
That might help to prevent evaporation of volatiles, however the caps would need to be removed each time before use. I'm awaiting your results with interest.
 
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Super Moderator
'84 CX650E that is evolving into a GL500
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18,678 Posts
They are vents. Vents can't... well... ventilate if they have caps on them.

BTW: I somehow missed welcoming you to the forum when you joined 2 years ago. Please add your location and your bike's model and model year (NOT year first registered as UK paperwork shows) 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 about 4 decades old and may or may not have had all of the maintenance necessary to keep it safe & reliable so if you haven't already done so I highly recommend downloading the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and going 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 (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). 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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Mr Honda put those vents there for a reason. If he had wanted them capped off they would have been factory-fitted with caps - and they werent . I think this is a bad idea - dont do it sir .
 

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1981 PC01 CX500 Custom
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57 Posts
Discussion Starter · #7 ·
Thanks folks for your responses. My intension is not restarting the "close vents or not" discussion again. Everyone may decide as he likes.

But since myself and other CX owners have made positive experience with blocking just these vents I just wanted to show a quick and easy way how to get hold of such caps.
If you don't want to block these vents then just don't do it.

Thanks reminding me to update my profile. Will do soon.

Take care and enjoy your CX
 

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'84 CX650E that is evolving into a GL500
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18,678 Posts
There is no debate. They are vents and blocking them will have well documented consequences.
In fact, a couple of years ago someone posted a way to extend the vents so that the openings pointed downward to shed water because his bike had problems in the wet that he traced to water droplets blocking the vents.
 

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Is the float bowl not also vented by the overflow tube?
 

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CX500 Z 1978 , Rickman Polaris fairing, currently GL500 front, Ignitech etc. subject to change
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320 Posts
New twist : someone in Germany recently suggested a 12v activated vacuum valve for the top vents, closed for engine off. Nice idea, may try that if and when I get 'round to it (if ever :cool: )

(for earlier tries : been there, done that, used several variations but removed all back to standard Honda design, problems in the wet with lines on upper vents, odd flat spots depending on routing of tubes. Just closing the tap now).
 

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Premium Member
1978 CX500 "The Grub", 1983 GL650I "Nimbus"
Joined
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12,243 Posts

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Registered
CX500 Z 1978 , Rickman Polaris fairing, currently GL500 front, Ignitech etc. subject to change
Joined
·
320 Posts

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Premium Member
1978 CX500 "The Grub", 1983 GL650I "Nimbus"
Joined
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12,243 Posts
Mine starts every time.
 

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'84 CX650E that is evolving into a GL500
Joined
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18,678 Posts
Mine started easily today after sitting since Friday. And if you saw some of the weather I've gone out in over the years you'd understand when I say that I doubt water droplets on the vents would have much effect.
 

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Mine always starts no problem and I always close the petcock. While my needle and seat are clean and work perfect, no one is capable of predicting when a piece of debris might hold the needle open and in turn leak gallons of fuel on the floor. I prefer to err on the safe side.
 

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Mine always starts no problem and I always close the petcock. While my needle and seat are clean and work perfect, no one is capable of predicting when a piece of debris might hold the needle open and in turn leak gallons of fuel on the floor. I prefer to err on the safe side. It takes less than a second to turn the fuel on or off so not much effort or inconvenience involved.
 
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