What is Reserve Capacity of Interstate Gas Tank?

[vic]

I installed an I/S tank on my Tourer about 3 years ago and put in a new petcock at that time.  I am wondering how much gas is approximately left when you switch to reserve on an I/S tank.  The reason I'm asking is that the last couple of fill ups, I've only had to put in 4-5 gallons of fuel after hitting reserve.

For example, yesterday, I hit reserve at 204 miles, drove another 10 miles to a gas station, and could only squeeze in 5.2 gallons of fuel (my fuel mileage is excellent).  If the I/S tank holds 6.9 gallons when full, and like most tanks, only has a gallon left on reserve, then I should be able to squeeze in more than 5.2 gallons after I've hit reserve. 

So does the I/S tank hold more than one reserve gallon of gas, or is my 3-year old petcock failing like I've been reading others' postson this topic?  Thanks in advance for any comments.

[Grandpot]

Vic:

Last month I measured the reserve capacity on my I/S by standing the bike upright and draining the gas until it went to reserve, then I drained the remaining gas from reserve into a container.  It was exactly 1 gallon.

If you rebuild the petcock, don't forget to install a new filter screen and run some carb cleaner through both channels of the petcock.

[Ricky-D]

It's been reported on this forum that the IS tank has somewhere around 1.3 gallons reserve. That could be different from a Std tank for a number of reasons.    Profile of the lower portion of the tank, different standpipe on the petcock.

There are also some reasons for the disparity of you experience in addition to the ones mentioned above.

Conditions of the ride at the time. You know, bumpy roads hills, etc.

Tank capacity is always the highest possible figure quoted from the manufacturer.

Rarely do any of us achieve a truly full tank, so how much off the total when we "fill" is surely relevant when you are figuring from the "full" end of the spectrum.

Easiest to determine reserve is to carry a small quantity of gasoline in a container (as a 2nd reserve) and run your bike out of gas on the reserve.  If you noted the mileage when turning on the reserve, it's a simple matter to figure out your  reserve mileage.

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[Joe Hummer]

Remember, you are never going to be able to fill the tank completely...not without pouring fuel out of the vent line at some point or another (either because the tank is too full or the fuel expands when it gets hot.

Joe

[Jess from VA]

The book says reserve on the 6.9 tank is 1.1 gallons. But the few times I have hit reserve and filled up only a mile or two later, no way I got in 5.8 gallons.

First, I don't think the 1.1 is an accurate figure, given individual diffences in each bike's build.  And if you have installed a pingle or other petcock, it may be completely different.

Second, most people don't truly fill their tank.  IF the gas pump will allow a slow enough feed, I have found that you can get almost a half gallon more gas in the IS tank, even when it looks to be full up to the neck.  Again, if the pump will allow a slow controlled feed (that doesn't surge or spash out on the tank), I routinely add small, slow feed amounts, topping up while gently rocking the bike back and forth with my hips (I never get off a bike to fill it when the cap is in the center of the tank....if you do it on the sidestand, you will never get a full tank).  I can get almost another half gallon in there even when the gas look full to neck, AND I have never had a drop leak out a vent/overflow tube.  When I do this, I do not lose my first Interstate led fuel gauge bar until  somewhere between 60 and 70 miles on the tripmeter (which I reset every fill-up out of habit).

[Kingbee]

Do you have an ADDED fuel filter?  Some of them add enough resistance to the fuel flow in a gravity fed system to force you to switch to reserve earlier than normal.  Personal experience.

[vic]

Thanks for all the replies so far. I always fill the bike up while I'm still on it and holding it upright.  I don't fill the bike on its sidestand.  Also, I don't have a fuel filter on it and have the stock (Keihin) petcock.  And every few tankfuls, I always add a bottle of Chevron Techron because I'm really paranoid about trying to keep the carbs clean.

[Ricky-D]

The only times I ever try to fill the tank is when on a trip.

The Valkyrie I/S is seemingly top heavy to begin with so having to carry around a bunch of extra gallons is just a waste of my effort.

I like to run normally with a half tank of gasoline to ease the handling of the bike.

Of course I recognize "different strokes", just thought I'd toss it in there.

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[Jess from VA]

Do you have an ADDED fuel filter?  Some of them add enough resistance to the fuel flow in a gravity fed system to force you to switch to reserve earlier than normal.  Personal experience.

No mods to my tank/filter screen/petcock on either Interstate; I am box stock as I have never had an issue with any of this stuff (knock wood).

Truth is, I have only hit reserve a couple times on long freeway hauls with corresponding poor mileage.  I think my reserve is closer to 1.3-4 than 1.1.  No big deal.

[Larry]

Do you have an ADDED fuel filter?  Some of them add enough resistance to the fuel flow in a gravity fed system to force you to switch to reserve earlier than normal.  Personal experience.

I agree, just put on a secondary filter and quick disconnect kit and noticed that I don't have the range getting down there that I used too. Not sure I like that.

[Bone]

You guys made me curious.

The manual list the tanks;
 6.9 gal/1.06 reserve
 5.3 gal/1.14 reserve.

[MP]

Mine is real close to the 1 gallon on reserve.
MP