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Discussion Starter #1
My '92 VN750 has a strange problem with cutting out when I am cruising and holding the RPM's around 4-5000. It feels like it is starved for fuel. It wont die or drop RPM's much, just kind of sputters for a bit. Giving the bike a little choke helps it when it sputters, but doesn't fix it. Giving it a little throttle will usually help also.

I also noticed today that strong gusts of wind make the bike cut out really bad. If I hit a big gust of wind, the bike almost stalls out. I tried opening the throttle when it was stalling in the wind and it did nothing. It just about died when I gave it throttle.

So, I am pretty sure I have a carb/intake problem.

I read somewhere about modifying vent hoses, but I can't seem to find it now. I've had this problem ever since I've owned the bike. It's just now starting to get on my nerves bad enough to fix it.

My guess is that it is lean, but I dont know if it is the carbs or something else. Anyone else ever had this problem.

What do you guys think? Carb? Air intake? Something else? If you need more info, just ask.

P.S. Carbs are clean and I always run seafoam in my gas. I don't see any issues with the carb/air boots either.
 

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My '92 VN750 has a strange problem with cutting out when I am cruising and holding the RPM's around 4-5000. It feels like it is starved for fuel. It wont die or drop RPM's much, just kind of sputters for a bit. Giving the bike a little choke helps it when it sputters, but doesn't fix it. Giving it a little throttle will usually help also.

I also noticed today that strong gusts of wind make the bike cut out really bad. If I hit a big gust of wind, the bike almost stalls out. I tried opening the throttle when it was stalling in the wind and it did nothing. It just about died when I gave it throttle.

So, I am pretty sure I have a carb/intake problem.

I read somewhere about modifying vent hoses, but I can't seem to find it now. I've had this problem ever since I've owned the bike. It's just now starting to get on my nerves bad enough to fix it.

My guess is that it is lean, but I dont know if it is the carbs or something else. Anyone else ever had this problem.

What do you guys think? Carb? Air intake? Something else? If you need more info, just ask.

P.S. Carbs are clean and I always run seafoam in my gas. I don't see any issues with the carb/air boots either.
there is a vent hose that runs from a tee at the carb vents that should run into a small opening that is just a holder for the hose,on the back side of the right air filter housing sounds like yours has fallen out or is gone.Check for about a half inch hose on the back of the filter housing if it is not plugged into that hole cut the end of the hose at about a 45 degree angle and push it back in there,if it is in there take it out and angle the end of it and trace it back to the tee at the carb and make sure it is attached and not kinked or has a hole worn in it.
 

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Old Twistie Sticks Rider
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What Denny said, but it may be jammed in and stopped off, it is a vent so it should be ok if not plugged, so the 45* cut should work...
Have a good one...Old Dog...
 

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Old Truck Junkie
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What denny and OD said, If that don't work be sure to check that wasps have not nested in the hose.
 

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Old Twistie Sticks Rider
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Couple of other thoughts, 1- if it happens to be a California bike it could be the pollution junk... 2- If it just does it after you run a bit it could be tank not venting and starving the carbs... You don't have to be in Cal. for it to be a Cal. bike, bought my 06 new in Tn. and it was a Cal. bike and gave me probs with the pollution junk...
Have a good one...Old Dog...
 

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Out of curiosity how do you know for if its a ca model? I am assuming that means California not Canada?
 

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Yahoo VN750 Group Owner
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What everybody else said. Since it is affected by strong winds, it is almost certainly that carb vent tube that is supposed to be stuck into the back of the right ear. I had this exact problem with my '86 after doing the ear shave and just leavin that hose hanging in the wind. Once I stuck it up under the tank so it was unaffected by wind, the problem disapppeared completely.
 

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What denny and OD said, If that don't work be sure to check that wasps have not nested in the hose.
that is exactly right ,I did a complete carb tear down on my300 4TRAX(since been stolen from me) before finding a mud daubers nest in the air intake almost completely blocking it off.But the happening at speed makes me think it is flopping in the breeze.I also forgot to tell him if it had been ear shaved to tie it up underneath the tank out of the wind,I put a lawn mower fuel filter in the end of mine and left one end open and zip tied it up underneath the tank. The filter lets it breathe and keeps the bugs out of the hose as well.
 

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Old Twistie Sticks Rider
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Out of curiosity how do you know for if its a ca model? I am assuming that means California not Canada?
Yes Cal. meaning California model... It will have 2-vent tubes coming from the rear of the tank, the one on the right side will go to the Cal. pollution control junk, the one on the left will be the normal tank vent and goes to the bottom of the bike and is open... There is also a page in the service manual (don't have my manual anymore) that shows the extra Cal. junk... HTH...
Have a good one...Old Dog...
 

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Discussion Starter #11
Thanks for all the suggestions guys. I just got a chance to work on the Vulcan today.

I have a few questions about what exactly I am looking for.

I see 3 vent hoses coming from the carbs. 2 of them were connected to the petcock. The other one was not connected to anything. Here are a few pictures of what I am looking at.

These are the 2 that were on the petcock.


This is the one that was not connected to anything.




Is there supposed to be a vent hose that hooks into the air breather? I can't find any hose close to mine.


Am I looking at the correct vent hoses? Also, I'm not sure which hose needs to be connected to the right side breather. Anyone have any advice? Thanks!
 

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Where is the vac hose in your first pic that should go from the carb to the petcock?
In the second pic.... that looks like the carb vent hose. It tees in there some place and routes to the back of the right ear in pic three. (not above the rear cylinder) If that is the carb vent in the pic,then that would cause your problem.
BTW..... what is that hose in the last pic going under the coolent hose?
 

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Man it sucks having that big ass airbox in there :(.

The first two hoses that came from the petcock are your fuel lines. The vent hoses in question originate between where those connect to the carb. That one hose that wasnt connected to anything is suspicious of the hose; especially if it was just chilling out right there.
 

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Here is a diagram:
http://www.vn750.com/photopost/showphoto.php?photo=1757&cat=503

I have not spent enough time working *hands on* the bike to accurately identify the hoses from the pictures you posted.

Three hoses go to the petcock.
The two hooked to the outside nipples are fuel supply to the carb bowls.
The center nipple on the petcock has a hose that connects to a vacuum port on the carb.
 

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On 2nd thought, it doenst look like there are any hoses coming out of the bowl vents. Reach your hand in there and see if you feel two nipples directly on top of the carb between where the fuel lines attach.

(edit)
Attached is the schematic. The red arrows point to where your lines originating from the petcock go. The ones between those in the yellow box is where your problem lies. If those dont have any hoses to them, 'theres yer problem.
(/edit)
 

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ok first pic.. your missing the small hose that goes from (as your sitting on the bike) the nipple on the left carb to the petcock.
2nd pic.. that appears to be the crank case hose.. it should go to the air valve under the seat.
3rd pic...i am guessing here.. but that is the one that goes to a "T" valve.. there should be a hose coming from the other carb to the same "T".. then there should be a hose comming off of the "T" to the right ear.
4th pic.. that is the emitions for the front cylendar... it should also go back to the air valve under the seat... follow the one coming from the back cylendar and you should find the air valve....you should also (as sitting on the bike) have a hose coming off of the right carb going to the air valve under the seat....infront of the battery box.
 

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Discussion Starter #17
Thanks guys.

To answer your questions:

1: The 3rd hose that hooks between the carb and petcock was on the tank still. It wasn't missing. I removed the hose from the carb side because it was easier.

2: The "hose: is the last picture is my plug wire.

Update:

After inspecting all possible problem areas and finding nothing else, I routed the carb vent hose (the one that is circled yellow) into my right side ear.

I checked the diagram that was posted earlier and all the hoses are there. 2 fuel lines to the carbs and 2 hoses into a "T". out of the "T" is the hose in question. (Yellow)

Problem:

With the hose routed into the right side ear, the bike barely runs. It will idle, but bogs terribly when given any throttle and will not hold rpm's with throttle.:doh:

So, I removed the hose from the ear and it ran great. It idles and revs well. The hose was not pinched or cracked anywhere either.

Now I don't know what to do with the hose. Obviously it needs to go somewhere, but the ear doesn't seem to work.
 

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I put mine in the frame under the tank......near where the two frame tubes split off at the front.
 

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cut the end of it at a 45 degree angle and put it back in the hole.. its easy to bottom that hose out...if left out of the ear it will cause you problems at speed.. kind of like a straw in cup.. you blow over the top of it and it will draw liquid out of the cup... it will do the same from your carbs.
 

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Old Twistie Sticks Rider
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cut the end of it at a 45 degree angle and put it back in the hole.. its easy to bottom that hose out...if left out of the ear it will cause you problems at speed.. kind of like a straw in cup.. you blow over the top of it and it will draw liquid out of the cup... it will do the same from your carbs.
+1 on that... Ask a friend who refused to put his beer away in a 90+ MPH bass boat...lol... As Clock said cut the end on a 45* angle and she should do great in the box...
Have a good one...Old Dog...
 
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