Vulcan 800A, Having to switch to reserve way too early

[De-Rock89]

Hi,

I am having to switch to reserve after only going about 95 to 100 miles. This is at about 2.5 gallons or so. The specs say my tank holds 3.96 gallons. I highly doubt the reserve is supposed to be 1.45 gallons.
I checked the tank vent line and its all clear. In my search for an answer I have read that people with the same bike as mine are going 130 to 150 miles before needing to switch to reserve. Everything is stock except the pipes are debaffled and all the EPA crap is removed and capped, except for the vent line to the petcock, that is still tied to the airbox like factory
Amy sujestions?

[De-Rock89]

correction, its tied to the intake, instead of the airbox like factory.

[XCR600]

What year is it ? My 95 would hit reserve around 95 -100 if I was in town being liberal with the throttle , riding @60mph on day rides I would get 130 -140 before reserve. I'm getting better mileage now that I changed my sprockets. 95 and 96 came with 16/46 , 97 up came with 17/42. I changed mine to 18/42 , whole different bike now , really lowered my RPM's = better mileage.
How do your plugs look ?

[XCR600]

Another thought is if your only putting in 2.5 gal after hitting reserve your tank screen on the fuel tap might be gunked up, or your fuel tap may have some issues.

[18wheelfixer]

This is one of those "it is what it is" things. I too thought my fuel filter screen on my VN800A2 was probably plugged so I pulled the fuel tap. I was surprised to see that the primary draw tube is enclosed inside the screen on the fuel tap and it is rather tall. There really is no fix that I am aware of. The brass primary draw tube cannot be cut down without sacrificing the screen. It's just one of those things where you are going to have to be aware that you have 1.46 gallons (or about 60 miles) after you switch to reserve.

Is that all that you're getting from 2.5 gallons is 90-100 miles? That's only 40 mpg. My V2K on my last tank got 46.1 mpg. If I remember correctly my VN800A2 got at least 45 on its worst day. Still, I guess it isn't out of the norm and to switch to reserve after 2.5 gallons is perfectly acceptable.

[mcgyverit]

My stock 96 I have to turn at 95 but have gotten as high as 120 before. We're you not having to turn on res that soon before?

[De-Rock89]

I've only had the bike about a month. It just seemed illogical for the bike to need to switch to reserve with 1.45 gallons still in the tank. Its a 95 with 16k miles on it. The plugs are slightly black and sooty but I don't believe the bike is actually running rich... is there a way of diagnosing the petcock without having to drain the tank and remove it from the tank?

[18wheelfixer]

is there a way of diagnosing the petcock without having to drain the tank and remove it from the tank?

Sure, run it low on fuel and then remove the tank from the frame and tilt it on its side away from the fuel tap. Once you remove the fuel tap you're going to notice what I was saying about the primary fuel draw tube. It has to be five inches tall sitting inside of the filter screen. You'll just have to live with it. It is normal operations on the VN800 carbed.

[De-Rock89]

I apologize if I sound redundant, but I dont exactly understand the mechanics of how that petcock works or looks inside the tank... So the 1.45 gallons that are in the tack at reserve is completely normal? Or symptomatic of this screen being clogged with stuff?

I wonder if there is a way to back flush it with gas to clear out the screen....

Also as a side question(and may have to do with my low fuel economy)... This is my first bike also... What are the safest range of high RPMs? I have to travel a highway where the average speed of traffic is 70 to 80. I think that is around 5000 to 5500 RPMs or so I believe.... I know bikes are supposed to operate at higher RPMs then a car... but that seems pretty high... My tachometer does not have a red line. its just numbers 1 through 9. (I plan to get 18/40 sprockets as soon as I have the money to do so)

[18wheelfixer]

I found a picture of a fuel tap that looks similar to the one installed on the VN800.



First thing I must say is the petcock changes nothing outside of the fuel tap. The fuel line runs fuel from the tap to the carb when it is in primary or in reserve. The difference is inside the tank. If you see the dark part inside the screen that is the primary draw tube. The reserve draws off the bottom of the fuel tap and has no tube, just a port that the fuel is drawn from. The reason why I know that your screen is not plugged is because the reserve is inside of the screen the same as your primary draw tube. If the screen was plugged both reserve and primary would not get fuel.

You never did mention which year your 800 is? If it is 1995-96 you have a 16/46 sprockets. If it is 1997 or newer it has 17/42 sprockets. Here is a link to what the rpm's are at highway speeds with the 17/42, 18/42, and 18/40 sprockets. The Wolf's Bike Shop; just how far do you trust me? All Vulcans love to run in high rpm's. You aren't going to get it to anywheres near an rpm that will damage the engine. If you have a windshield on your bike you'll find out about the death wobble before you ever find the top end.

[De-Rock89]

Its a 1995.

[XCR600]

Camera 6 - 29-2011 009.jpg
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Here's a pic of my old vs new , this is what yours looks like . The main pick up tube is clearly visible however your not likley going to see any thing wrong with it, the problem will be in the valve itself.
Your is as old as mine was if it's never been replaced. You can test it on the bike.
Bike OFF !!
Get a funnel & empty gas can , remove the hose attached to the bottom of the petcock / fuel tap and hold the funnel under it to drain into the gas can.
In the ON & RES positions NO gas should be flowing, a few drips then nothing is ok.
In the PRIM position gas should / will flow freely. If you have a constant drip or drizzle of fuel in the ON or RES position your fuel tap is leaking .
You can rebuild it but I would strongly recommend replacing it, save your self the trouble and time I went through only to buy a new one 9 months later.
I also have a pic of my floats that were vary dark and bad , I replaced those also. Just an FYI rubber and plastic don't age well in modern fuel , 17yrs takes it's toll on these parts.

[bugser]

I've only had the bike about a month. It just seemed illogical for the bike to need to switch to reserve with 1.45 gallons still in the tank. Its a 95 with 16k miles on it. The plugs are slightly black and sooty but I don't believe the bike is actually running rich... is there a way of diagnosing the petcock without having to drain the tank and remove it from the tank?

I don't see how your petcock would affect mileage. The gas is metered through the carb. If you are getting to much fuel, your plugs will be black and sooty.

- Spark Plug Inspection and Maintenance (The Garage - General) - CycleFish

Are you absolutely certain the carb is stock?

[garymc]

I get 38mpg on most tanks with my 2005 800b. I hit reserve 90 to 105 usually. I drive it hard, though. If I keep speed down to 50-55 I can get 45 MPG._

[De-Rock89]

New development. I hit 101 miles then had to switch to reserve. Then at 107 it seemed to run dry. I was sputtering into the gas station and it died a few times and had restart. I get to the pump and the tank maybe had 2 or 3 inches of gas in it. I only had to put in 2.665 gallons to fill up. That means there was still almost 1 and a half gallons still in the tank. What the heck?!?!

[XCR600]

Do you have an inline fuel filter , prolly below the petcock ? This could be getting clogged , lower fuel level = lower pressure and my not be able to push fuel through it once it gets low enough.
If you don't have one then as some one mentioned your venting my be restricted ,popping the cap open would tell you pretty fast if thats the issue. I removed the flapper valve from my cap and it's functioned great ever since.
Lastly your fuel tap may just be ready to be replaced.

[18wheelfixer]

New development. I hit 101 miles then had to switch to reserve. Then at 107 it seemed to run dry. I was sputtering into the gas station and it died a few times and had restart. I get to the pump and the tank maybe had 2 or 3 inches of gas in it. I only had to put in 2.665 gallons to fill up. That means there was still almost 1 and a half gallons still in the tank. What the heck?!?!

Pull your fuel tap and see if the screen is plugged. For $77 you can replace the tap if the screen does look horrible.

[XCR600]

@ Bugser I don't believe he has a low mpg problem as much as a flow problem , being he's only putting in 2.5 gal after hitting reserve.

@18Wheelfixer I would bet it's in the valve itself and not the screen , vac diaphragm leak ,or rubber is coming apart clogging passages , some thing like that.

[bugser]

@ Bugser I don't believe he has a low mpg problem as much as a flow problem , being he's only putting in 2.5 gal after hitting reserve.

@18Wheelfixer I would bet it's in the valve itself and not the screen , vac diaphragm leak ,or rubber is coming apart clogging passages , some thing like that.

Roger that. After reading the posts a few more times I finally got it...

[goddarddr]

???I consistently get 50mpg on my 95 800A since I bought it used in 2006
even now with a small 2.2 gal tank intake/exhaust/EPA performance mods