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Discussion Starter #1
What would cause the carbs to act like they are running out of fuel while doing steady speeds 45mph and above?
Vulcan rides great with lots of power till you get into 5th gear and steady out
the ride.
Starts dogging or chocking like she's near empty. Gets worse and she dies a mile later. Look things over and hit the start and nurse her home.
Did the air vent in tank, even ran bike with lid open and same results. Cleaned the petcock and cleaned the already clean tank filters. Clean gas coming from drains.
SeaFoam was added 50 miles ago to full tank and did nothing. Runs great till you steady speeds out at 45mph or above than dogs out eventually dying.
Only thing I can think of is carbs are out of sync. Maybe float(s) sticking?
Sqirt gumout up carbs drain butt? Ideas???
 

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Linkmeister Supreme
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Not sure?
Maybe carb vent hose to right airfilter box has fallen out, or pushed in too far and is blocked?
Check it, and cut end off at 45* angle before relacing it into filter box to prevent it from ever getting bottomed out and blocked.
 

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Discussion Starter #3
Are you talking the hose that runs on top of right carb to the air box above that?
Noticed it didn't have a grommet end! Hmmm, yet another manufacture defect!
Let me know if that's the hose you be referring too and I'll cut to 45 degrees and see what happens.
Thanks for your input.
 

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Linkmeister Supreme
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See Crobins post #9 in link below.
http://www.vn750.com/forum/showthread.php?t=15056&highlight=carb+vent+hose

I haven`t got under there yet myself to see exactly where it comes from, but from what I can see in diagrams the hose comes off a "T" from both carbs and goes to the filter box.

I just pulled the ears off my bike yesterday, and the hose just fits into the plastic cylinder with a full length slot in it. There is no grommet needed that I am aware of.

Do a search on the words "carb vent hose" for several more threads on this topic.
 

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Discussion Starter #5
Oh, at the "T"
Had a feeling it was a common issue. Just couldn't find the forum post.
Must have worked for Mitch!! He never replied.. lol

Thanks for the link and verification..
 

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Linkmeister Supreme
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Good luck with it.
 

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Discussion Starter #7
Well, Am getting "T"'s confused. Am sure you are referring to the smog control "T" and the elbow hose that's pressed between top of right carb and the plastic air thing.
 

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Discussion Starter #8
Okay, followed other forums.. Found the two hoses coming from carbs leading into a "T"
After the "T" it goes into the purge tank!!
My Vulcan's a blasted California model!!

What about the hose with no grommet leading to to the air box above carbs? One I'm looking at is on the right side pressing up on top of right side carb fitting in air box.
Is that the one to cut at 45 degrees?
 

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Okay, followed other forums.. Found the two hoses coming from carbs leading into a "T"
After the "T" it goes into the purge tank!!
My Vulcan's a blasted California model!!

What about the hose with no grommet leading to to the air box above carbs? One I'm looking at is on the right side pressing up on top of right side carb fitting in air box.
Is that the one to cut at 45 degrees?
Yes that is the one to cut at a 45.
 

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Old Truck Junkie
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Also make sure that the vaccuum hose from the petcock is in good condition. That meaning that it is not cracked and leaking air in.
 

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I sooo,misread the title on this one,The way it was worded I thought I was going to see a dog running faster than 40MPH, excuse me while I have a :doh: moment.
 

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Discussion Starter #12
Wow... lots of '93's Bald... You got MY bike!!! LOL

Yes, I checked all over till 1am. Think if hose dimensions in other forum
were mentioned it would have been easier. Not any of the small lines
It's the nickel size hose on right side leading to top air box. Cut 45 degrees!
 

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No not the big hose. That goes to the read valves that people plug off. The small hose goes into the top of the right breather cover. If you look with a light..just under the tank you can see where the "T" comes up just between the back of the carbs. This hose goes to the channel in the filter cover.

Yeah I noticed your 93'. You know the blue ones go faster.
 

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Discussion Starter #14
Awww Rats.... Well, I saw the "T" that connects to both carbs but the hose connects to the canister. CA model! You people saying to unhook from canister and cut a 45 degree and let it dangle?
 

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Discussion Starter #15
Well, I pulled the hose leading to the canister purge. Same hose that leads to that famous "T" that splits to carbs.
Unfortunately, that didn't clear it up. Still wants to jerk and dog out a bit at highway speeds. Added some more Sea Foam but still the same 'ol same 'ol...
Had a bike shop tell me today its the petcock diaphragm.. Huh?
 

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Discussion Starter #17
So, you agree it could be the diaphragm? Seems weird it only occurs after 45 mph.
I can cruise all day at 40 with no bucking, or dogging out. What I mean is the motor runs
the same at 4k rpms no matter what gear and logically should use same amount of gas in any gear at 4k rpm.
Can you explain why you think the same as local bike shop? Geee, never had a diaphragm go out on me... leaky petcocks but never a diaphragm. weird!!!
 

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Not saying I agree with the bike shop.
I misinterpretted your "Huh?" about the petcock diaphram, as meaning you didn`t know there was one.
I just posted the link to show you where it was.
Not easy to know or remember all the time how much wrenching experience a new member has.
 

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Discussion Starter #19
I got some experience with older bikes but not from a bike like this one.
Haven't had her very long and the jerking at 45mph or above only started
after replacing the stator last week. Vulcan is clean and all the hoses show no wear
or drying out. After a week now of running down hoses, wires, connections and possible leaks I even pulled the petcock to examine tank filters. I was VERY careful reassembling and should be fine! Maybe I need a list of EVERYTHING that could cause a great running bike to dog out at 45mph and above. Am beginning to give up!! Petcock diaphragm? Really?
 

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Discussion Starter #20
Well... I've ran out of possible ideas. All my hoses appear "like new" condition and hooked up correctly. After no answers to the beloved hose from carb "T" leading to purge in charcoal canister I checked and it made no difference attached or free flowing.
Not that willing to change system that worked great before stator replacement and learned the petcock diaphragm joins the list of most likely things to go wrong first on your vn750. Whats next my Spline?? Guess I best get on that too!!!! Thought VN750 was a great bike. What would have been great is if the frame bar came off on the left side not the right!!! You'll see on your next stator!!! GRRR!!!! Petcock Diaphragm! REALLY???? We'll see in about a week! Thanks for all the input and suggestions.
 
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