6 gal tank but only putting 5.5 gal when run empty

[PoorUB]

These are all reasons why I use the guage as a reference,  but use the odometer for accuracy.

I don't know how one can just go by the odometer. With my Harleys I could be getting 30 MPG or close to 50 MPG depending on conditions. That is a range of 150 miles to 250 miles to empty. My BMW is even worse! Mid 30's to 60 MPG depending on conditions, or 225 to 400 miles. I ride strictly by the miles remaining readout and the gas gauge. I never worry about how far I have gone on the tank. Sure the gas gauge is inaccurate, but it errors to the conservative side. It may say empty, but there might be 40 miles left in it.

[Dan89flstc]

Fuel density plays a role in capacity. Pump gas is very inconsistent as far as its weight is concerned. I sell Racing fuel so I have to be cognasent of these things when customers are looking for answers about fuel.

Fuel density has nothing to do with the capacity of the tank.

Fuel dispensed at the pump is measured in volume, and tank capacity is measured in volume.

A 5 gallon bucket holds the same amount of fluid, whether it is water or lead...

[Ohio HD]

Fuel density plays a role in capacity. Pump gas is very inconsistent as far as its weight is concerned. I sell Racing fuel so I have to be cognasent of these things when customers are looking for answers about fuel.

Fuel density has nothing to do with the capacity of the tank.

Fuel dispensed at the pump is measured in volume, and tank capacity is measured in volume.

A 5 gallon bucket holds the same amount of fluid, whether it is water or lead...

[Appowner]

Just wondering but I'm assuming the 6 gal capacity came from the MOCO specs/advertising.  So just how did the MOCO come to that figure?  Anyone know?  Was it some convoluted math formula or actual, physical testing?  With or without the guts?  And did they leave an air gap or fill to the brim?  And could they have rounded the number up at all?

As the bike sits upright is the fuel pickup at the lowest point of the tank?  Just how much gas might be below the pickup or even in some other part of the tank that doesn't fully drain to where the pickup is?

And how much air gap did you leave in the top of the tank when you filled it?  I'll wager the MOCO filled it to the very top in their test.  Assuming they did such a test.

I wouldn't worry about a gas pump that says you put (and paid for) only 5.5 gal in a 6 gal tank.  If indeed you have a 6 gal tank and filled it completely then that's a half gal of free gas.  I'd be more concerned if the pump said I put 7 gal in a 6 gal tank.  That's a gal of gas I'm paying for but not getting.  But I'd be surprised to find a pump functioning normally that is that far off.  Especially at today's prices.

[smoserx1]

So just how did the MOCO come to that figure?  Anyone know?  Was it some convoluted math formula or actual, physical testing?

Long time ago I was reading a thread somewhere about center stands on baggers and one of the posters said on the center stand he could get about a half gallon more gas in like that.  Makes sense.  A lot of the tank capacity goes away when the liquid lever reaches that "arch" where the tank sits on the frame backbone and when that happens the level starts dropping faster than before at the same consumption rate, but there is even more to it.  When sitting on the side stand the surface level is actually true but since the tank is tilted will appear higher in the left side of the tank, and on my bike that is where the sending unit is.  My gauge will absolutely read higher when the bike is on the sidestand.  That is why I am thinking the capacity (however it is figured) is based on a  straight up tank.  I really doubt temperature expansion of fuel or pump inaccuracy is enough to make a noticeable difference.  But for instance a lowered bike with  the same sidestand (which now sits up straighter) could make a  difference you could discern.

[Yellowbird]

Before you ask, and NO I don't do this on the reg. I went on a outing with the boys. Low fuel light was on and I was
planning on stopping at my Shell gas station. Arrived at my house and realized I didn't stop at the Shell.

Anyway, next day road to back to Shell gas station which was 2 miles away and topped off the 6 gallon tank.

Again just to show everyone, and NO I don't run this low all the time.


YB

[Appowner]

I have a good 40 miles left or more than a gallon when my low light comes on.  Just saying.

[chaos901]

We just finished a trip out west and I had at least 1.4 gallons left when my fuel light came on. 

[kd]

I just noticed my 2011 touring owners manual states the fuel light comes on at 1 gallon (3.8 litres) remaining. Knowing your mileage can be very helpful.

[Ken R]

When you say you put in 5.5 gallons, have you run it out of gas, or are you just looking at the gas gauge?

The gas gauges are very conservative. I could go another 20 miles after everything said I should be walking, and still had gas. A couple times when my miles remaining were at zero and the gauge was way past empty I ran another twenty miles.

If you really want to know how far you can go, toss a gallon can of gas in the trunk and ride until you run out. Toss in the gallon and run to the closest gas station and fill up. Then you will have a better idea of how far you can go.

Mine is very conservative.  But I have a PowerVision on the bars all the time and can see to within a few 100dths of a gallon how much I've used.  It's uncannily accurate! 
Every gas stop on our 4,500 mile trip the last two weeks, within 1/10th of a gallon compared to the station pump.
When my gas gauge says I should be walking, I have only used 4.9 to 5.1 gallons (according to the PowerVision).

Try this:
Siphon the tank dry.  Then put exactly 3 gallons into the tank. 
Hop on and ride around the neighborhood.  (static testing is useless).  The gauge should settle down to show a half tank on the nose. 
That should be good enough. 

I'm convinced that the fuel pump/fuel level sensor assembly float arms get slightly bent when being installed at the factory.  It's really tough to get all that stuff through the hole and set right.
I've adjusted several motorcycles by bending the arm slightly to indicate more or less fuel.  Once adjusted, it stays adjusted.

Ken