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Discussion Starter #1
I didn't know where to put this, but im gonna try here....

Well yesterday I experienced my first small but real problem on my Vulcan...

First off I will start with, Sunday I broke off the door cover to my bike and until then had never read the little sticker inside stating I should be running 91 or higher octane in my bike. Prior to this instance I had noticed a slight stalling problem on starting from a stop at a light or something when running on 93. So I switched back to 87 as the 93 was from a crappy gas station.

But i figured I would again fill from a better place with 93 that morning due to what I read on my now broken door cover :mad: Everything seemed fine, no issues, bike ran great, was a short ride with a decent breakfast in between. Haha!

Then rode to work Monday and back no issues as well as yesterday (Tuesday) all about 35-50 minute rides depending on traffic and which route I took. I decided after I would swing by my place, grab a glass of water then head to my folks place another 45-50 minutes away.

Now at this point, I was at about 80 miles into my tank of 93, figuring i had plenty of gas... So I'm cruising, knowing full well i have plenty of gas until i get to my hometown and id fill up when i was leaving... well my gas consumption went way down, I mean I think i get around 130 miles on a tank with a 2.4-2.5 gallon fill each time, this fill it was more like 95-100 miles if I was lucky (not sure as I didn't reset the trip counter).

So anyways, about 3/4s the way there, the bike starts bucking like its running low on gas or being starved, so I pull over immediately and the bike cuts out. try starting with bike in 1st... nothing, try in neutral... nothing. Put the fuel switch to reserve, again, nothing. Put fuel switch back to out. I then pull the key out, open and close tank cover, and slosh the bike side to side to make sure i'm not out of gas completely and there was still a decent amount in there.

Let her sit another second and bam she fired right up, and off I was with no issue. Filled her up (with 87) when I got into my town, let her sit about 40 minutes while i visited the folks and then headed home again, with no issue at all.


Now I cruise at around 3500-4500 rpm based on gear and speed I'm traveling. and generally am in 2nd, or 3rd gear while doing so. and I had been riding about an hour and 45 minutes which is probably not my longest stint on the bike at once yet....

My bike wasn't overheating, no out of the ordinary lights on, everything seemed fine, just this random bucking...

What the hell happened?!?!? is this the phantom out of gas thing i've seen mentioned here?

Is there something I should check/replace?

P.S. by the end of the ride home, I thought my keister had fallen right off of me... man I wish that meanstreak seat didn't push me forward so far...

would one of those AGM batteries or new spark plugs prevent this from occuring again?

Thanks, and sorry for the long winded post.

P.S.S. I would also like to add that I was at 6668.5 miles when this happened... LOL
 

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Old Truck Junkie
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4,133 Posts
1. Some of us find that the problem is a lack of venting into the fuel tank.
2. And also some of us have found the problem to be in the safety switch at the stand.
3. Others have found a problem with the ignition switch.
4. The vaccuum line to the petcock can also cause this.

This is the order that I would take to check this ideas out.
Hope this helps you.

Check the vulcan verses for more indepth information.
 

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Discussion Starter #3
hmm that morning i did hear a venting sound, when another guy from work went out to show me how to put the bike up on the center stand... as soon as it was up sitting it was a slight whistle or tea kettle sounding thing... followed by the scent of gasoline...

Thanks for the quick response!
 

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Old Truck Junkie
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4,133 Posts
hmm that morning i did hear a venting sound, when another guy from work went out to show me how to put the bike up on the center stand... as soon as it was up sitting it was a slight whistle or tea kettle sounding thing... followed by the scent of gasoline...

Thanks for the quick response!
We need air going into the tank as it empties out, but the EPA doesn't want any air coming out of the tank.

The verses are are a wealth of information.
You are welcome.
 

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Love My Baby
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1,165 Posts
Sunday I broke off the door cover to my bike and until then had never read the little sticker inside stating I should be running 91 or higher octane in my bike.
Guess you have a meanstreak and not a 750. My 750 only needs 87 octane. In fact, burning higher octane is more problematic in the 750.

I was at about 80 miles into my tank ...the bike starts bucking like its running low on gas or being starved, so I pull over immediately and the bike cuts out. try starting with bike in 1st... nothing, try in neutral... nothing. Put the fuel switch to reserve, again, nothing. Put fuel switch back to out. I then pull the key out, open and close tank cover, and slosh the bike side to side to make sure i'm not out of gas completely and there was still a decent amount in there.

Let her sit another second and bam she fired right up, and off I was with no issue...

What the hell happened?!?!? is this the phantom out of gas thing i've seen mentioned here?
That sounds like a textbook example of the phantom out of gas syndrome. Once you opened the tank she started right up. Check your gas cap vent.
 

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Calif Rider
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725 Posts
The phantom out of gas thing I think everybody has had this happen to them. Some of us have never really found out what causes it. It is really hare to pin down, like it was said it most likely has a lot to do with a vaccuum problem. With no vaccuum, no gas will flow from the petcock to carbs. I have had this several times and you never know when it will happen. I traced the fuel lines last week and saw that they have to go up and over to carbs, rerouted the lines. Now the left gas line from petcock goes to front carb it is shorter and does not go up to feed front carb. Then did the same with the right gas line that now goes to the back carb, now a more of a straight drop to carbs. This may help if yours are not this way, it sort of makes sense. Both lines had to be cut to fit properly.
 

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The Reanimater
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847 Posts
There is also a thing called Vapor-Lock. It's when the fuel in the gas line gets hot enough to turn to vapor. Then it's like a plug in the gas line. It doesn't let fuel flow throught it.

Let it cool for a while and it will turn back to liquid and the fuel will flow again.

So it might be more Heat Related then Vacuum Related.
 

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Search Goddess
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2,002 Posts
If you do have a VN750.. just with a meanstreak seat.. then it will run just fine and dandy on 87 octane. The 91 is a RON (Research Octane Number) octane rating which equates to about 87 (AKI)pump rating

Research Octane Number (RON)
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.

Motor Octane Number (MON)
There is another type of octane rating, called Motor Octane Number (MON), or the aviation lean octane rating, which is a better measure of how the fuel behaves when under load as it is done at 900 rpm instead of the 600 rpm of the RON[2][3]. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, a higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON. Normally, fuel specifications require both a minimum RON and a minimum MON.[citation needed]

Anti-Knock Index (AKI)
In most countries, including all of those of Europe, and Australia, the "headline" octane rating shown on the pump is the RON - but in the United States, Canada, and some other countries,[which?] the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI). It may also sometimes be called the Road Octane Number (RdON), Pump Octane Number (PON), or (R+M)/2. Template:Conversion?

Difference between RON and AKI
Because of the 8 to 10 point difference noted above, the octane rating shown in the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel.


"regular" gasoline in US and Canada 91–92 (RON) 82–83(MON) 87 (AKI)
 

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Love My Baby
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1,165 Posts
Thank you Dianna. I thought there might be a difference in octane ratings in different countries but I didn't know exactly what. I was a bit confused about the initial post and the 93 vs. 87 thing.
 

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Premium Member
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641 Posts
Like many of the others have said, 87 is just fine for our bike. As to the other problem, what has been deemed the phantom gas syndrome, I found an easy fix that someone else posted on here. There are two white plastic pieces with vent holes in them in the gas cap that have a little red diaphragm on them. I just pulled these two pieces out of the gas cap and haven't had a problem with the phantom gas syndrome since. I'm guessing that these pieces help keep more of the fumes venting out the vent hose rather than the gas cap and is probably one of those EPA things but doesn't seem to hurt anything if you take them out.
 

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Discussion Starter #12
Thank you all for the clarification on these things. I guess I read it and figured, what the hell. Knee Jerk reaction I suppose.

I guess i'm not sure entirely what to blame it on (other than the 93) as the bike was on for a long stretch of time, but I dont believe it was overheated. It may have been a little warmer than normal because up here in northern mass we've had a few days of mid 90s and high humidity weather.

Unfortunately i'm not a super mechanically minded person so I didn't even know where to start with this. It didn't happen on the return trip and has only happened once. Reading these tutorials is very intimidating, especially the final drive spline lubrication process.

as of right now the bike is working very well, and I'm trying to keep the "if it aint broke, fix it some more" attitude out of my head at this point in time. I don't even know how long im going to keep this bike, I feel very cramped on it and the seat is uncomfortable!

I will continue putting 87 in the bike, I just bought the AGM battery from Advanced Auto Parts, and priced the NGK Iridiums out at $7 a piece, which would need to be ordered.

I plan on installing the battery to start when I get to work mounting the Mean streak seat I bought and relocating the blinkers and helmet locks this weekend sometime.

I need to buy a torque wrench and a full ratchet set, as i just this past year moved out of the folks place and always had what i needed in my fathers massive tool collection, but now im on my own. lol
 

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Linkmeister Supreme
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7,960 Posts
Don`t be afraid to try working on the bike. Mostly it is pretty straight forward, and there is lots of help here if you need it.

I know what you mean about the bike being a bit cramped. If you are a big or tall guy, the frame seems too short. I hope the "Meanie" seat is more comfortable for you.
 

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Discussion Starter #14
Don`t be afraid to try working on the bike. Mostly it is pretty straight forward, and there is lots of help here if you need it.

I know what you mean about the bike being a bit cramped. If you are a big or tall guy, the frame seems too short. I hope the "Meanie" seat is more comfortable for you.
Thanks,

I'm not completely numb with my hands, but i've never been a motor guy, more of a computer/tech nerd haha.

I hope the seat makes it more comfy for me, it actually pushes me farther forward as it sits with the front tongue pushed all the way forward.

To give you an idea.

When I sit on the stock seat, my knees just touch the wing on the tank emblem, when i put the mean streak seat on, my knees are half way or more through the center of the tank emblem. I'm thinking of trying to add a tongue to the front, and maybe pushing the seat further back, I like the idea of mounting the back fender screw into the tail light housing instead of the fender, this would be achieved by pushing the seat farther back when mounting. Is that front tongue really necessary with the 2 side brackets and the rear bracket? hmm...

I just think I need a bigger bike.. bah
 
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