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Discussion Starter · #1 ·
So my bike started running a little choppy at idle, idle wasn't staying put etc etc. so after cleaning the bike i started it up and heard what i thought was a vac leak. upon further inspection i found this lil doodad on my carb and it has nothing attatched to it. Put my finger over it and there's def. Vac there and the idle instantly smoothed out.

The question is what is supposed to be attatched to this thing. I put a plug over it for now but i'd like a permanent and proper fix. Thanks in advance.



 

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Discussion Starter · #3 ·
Air filter is under the seat, you get to it by taking the right side cover off. but no there is no line supposed to go to the airbox from there.

I've looked in the manual and not found this nipple or any tubing in any diagrams, nor have i seen it looking at the microfiche on bikebandit
 

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I've been attaching my little hose from my emissions system vacuum switch thingy to it... maybe I'm wrong...kinda new to this bike.
 

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Discussion Starter · #5 · (Edited)
emissions system vacuum switch thingy? I don't believe i have one of those, Hmmmmm lemme see what the diagrams on bike bandit say on that.

Edit: Nope, don't have one.
 

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is it for doing a carb sync? ---does the other carb have one in the same spot?------if its running ok with that cap over it, i wouldnt worry to much about it---it probably is some emissions switch source
 

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I think my left hand carb has the nipple, but its not drilled. The right hand one has drilled. I'm currently researching it myself. It's official name of the "thingy" is Evaporative emission carburetor air vent control valve. I have a few 4 letter names for it myself :)
 

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Discussion Starter · #8 ·
is it for doing a carb sync? ---does the other carb have one in the same spot?------if its running ok with that cap over it, i wouldnt worry to much about it---it probably is some emissions switch source
No there's nothing like it on the other carb. it's definately a vac source for something. The carb sync ports are on the heads themselves.
 

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yeah that was a long shot---i figured the ports were on the heads----i know my brothers 82 Suzuki has a vacuum operated petcock that hooks to a nipple like that on one of the 4 carbs----hook a hose to it and run it up inside your full face helmet for ventilation;)-
ill ask some of my sources and try to get back to you soon
 

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my carbs don't have an opening there i checked all 3 of my vt500s and none of them have that. your carbs may be off a newer bike. the newer models with emissions probably use it. cap it and forget it
 

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my carbs don't have an opening there i checked all 3 of my vt500s and none of them have that. your carbs may be off a newer bike. the newer models with emissions probably use it. cap it and forget it
Thats a d*mn fine answer--i would go with that--plus my brother and dad are named Ernie, so i really trust him
 

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Discussion Starter · #12 ·
LOL haha.......yeah i'll get a proper cap on it tomorrow. right now it's just got a hose with a screw in it for temporary. My vacuum petcock goes to the rear cylinder head sync port (which is where the manual says it should go)..... It's really odd though that that little port all of a sudden opened up. I know i never heard a vacuum leak there before.
 

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LOL haha.......yeah i'll get a proper cap on it tomorrow. right now it's just got a hose with a screw in it for temporary. My vacuum petcock goes to the rear cylinder head sync port (which is where the manual says it should go)..... It's really odd though that that little port all of a sudden opened up. I know i never heard a vacuum leak there before.
Plastic factory cap dry rotted and fell off.
 

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It's no fun running from my 'puter to the garage and back!

The item in question on my '84 looks like a plain metal rod sticking out, about 2cm/1" long. pewter/plain matt metal in colour. I have no hole, no vaccuum. This metal post is non functional in appearance. Nothing attaches to it.

My maintenance manual also does not mention it. Because this is the rear part of the carb there is not even a photo. There seems to be no serviceable parts on the rear of the carb. plug it as you did and life is better. Maybe the previous owner mistakenly drilled it out? Maybe the factory metal cap vibrated off?
 

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LLL-if-I-know ;)
{That`s a cross breed between = an elephant and a Rhino)
But please let us know what you find out about this "thing"...
Stumpped,
Dennis
See ya in Sturgis?
 

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Discussion Starter · #17 ·
It's no fun running from my 'puter to the garage and back!

The item in question on my '84 looks like a plain metal rod sticking out, about 2cm/1" long. pewter/plain matt metal in colour. I have no hole, no vaccuum. This metal post is non functional in appearance. Nothing attaches to it.

My maintenance manual also does not mention it. Because this is the rear part of the carb there is not even a photo. There seems to be no serviceable parts on the rear of the carb. plug it as you did and life is better. Maybe the previous owner mistakenly drilled it out? Maybe the factory metal cap vibrated off?
No idea, i know it wasn't leaking vac before, so it must have been capped and fallen off. O well, lol
 

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Discussion Starter · #18 ·
Little update. There is in fact one of these ports on the other carb as well. It's hidden behind the throttle linkage and i couldn't see it in the dark last night. That side has a dab of glue inside the hole so i assume what happened is the glue on the right side carb came out. I have capped it and all is well. I may use these ports for syncing since they're easier to use than the heads and SHOULD provide the same (if not better) results.

Thanks again guys.
 
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