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Discussion Starter · #1 ·
Hi everyone! I have two unaccounted for lines that come from the carburetor and presumably to the gas tank. I know one of them is a fuel line, and I assumed the other was a vacuum line, but there doesn't seem to be a place to put it. Can anyone point me in the right direction?
 

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'84 CX650E that is evolving into a GL500
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I think those lines should go to the other side of the bike and attach to the petcock. The larger one that is attached to the pipe that runs between the carbs is the fuel line and the smaller one that attaches to the left side of the right hand carb is the vacuum line.

I'm not 100% sure but I think they changed from the original non-vacuum petcock to the later vacuum type at some time during the 1980 model year and without knowing what your friend and all other the people that owned the bike changed over the last 4 decades, it is possible that you may have an early '80 petcock and late '80 carbs.
Or that someone replaced a leaking vacuum petcock with a non-vacuum one (this is a common change - my '84 CX650E based machine has had a non-vac petcock for about a decade and I was far from the first).
Or that you have a vacuum petcock and don't recognize it as such. The non-vac type has just one hose barb for the fuel line but the vacuum type has the barb for the fuel line plus 2 smaller barbs that point back under the tank for the vacuum line and the drain/vent line to connect to.
If you post a pic of your petcock we can tell you which type you have.
 

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Discussion Starter · #5 ·
I think those lines should go to the other side of the bike and attach to the petcock. The larger one that is attached to the pipe that runs between the carbs is the fuel line and the smaller one that attaches to the left side of the right hand carb is the vacuum line.

I'm not 100% sure but I think they changed from the original non-vacuum petcock to the later vacuum type at some time during the 1980 model year and without knowing what your friend and all other the people that owned the bike changed over the last 4 decades, it is possible that you may have an early '80 petcock and late '80 carbs.
Or that someone replaced a leaking vacuum petcock with a non-vacuum one (this is a common change - my '84 CX650E based machine has had a non-vac petcock for about a decade and I was far from the first).
Or that you have a vacuum petcock and don't recognize it as such. The non-vac type has just one hose barb for the fuel line but the vacuum type has the barb for the fuel line plus 2 smaller barbs that point back under the tank for the vacuum line and the drain/vent line to connect to.
If you post a pic of your petcock we can tell you which type you have.
That makes sense! I’ll make sure to grab a picture of the petcock later.

If I have a petcock that doesn’t have a vacuum line, won’t gas not flow or am I mistaken?
Thanks for your help and explanation I learned a lot!
 

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If you have a vacuum petcock fuel won't flow unless the vacuum line is connected. If you have a non-vac petcock you will need to cap the vacuum port on the carb.
 
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