The light on my 2013 Iron comes on at about 95 miles on average and it will take 2.1 gal to fill up if I do it right when the light comes on. I've had it go as far as 120 miles before it lit up (all highway run) and as low as 82 miles (all city and getting on it more). No engine mods, all stock. I've got 6,500 miles on it so far.
It's really consistent most of the time since I use Shell 93 octane only, when I can. If I use different gas it will change some but not a whole lot as long as I use hi octane.
I went 155 miles on one highway run before filling up, that's the furthest I've pushed it, of course the light was on at 120. I don't like to push it that far at all unless I have to.

 

During a recent ride I had mine come on at 100. I stopped and called my riding buddies and told them I needed to gas up. While I was waiting for them to turn around I removed the cap and looked inside. I shook the bike a bit to see how much gas was left and when I turned my bike back on the light was out. The light remained out and did not come back on during the 10 mile ride to 7/11. So really who knows? Now I gas up at 100 and I average about 45mpg (2013 XL1200C).

 

Some folks believe that the pump must remain submerged to be properly cooled, that is not the case, the fuel being pumped through the pump/pump motor is what cools the pump, so as long as you don't run it dry you should be ok....not arguing just clearing up what you said...

 

Mine does this all the time...this is normal. The float that flips the light on is based on the fuel level on the left, slightly behind the center of the tank.

If you are in a left turn at some speed, centrifugal force pushes the gas to the right side of the tank and can make the light go on. Once it is on, it will stay on until the key is switched off.

This can also happen if going up or down a steep hill.

Then when the bike is level again, and you have turned the key off and back on, the light will not come back on because the fuel level is not low enough to trigger it on.

 

sportster manual from HD says comes on with one gallon left in tank. So putting in 2 gallons on fill up would be about right. Just know that you can take it a bit farther when the light comes on.

 

I just installed a 4.5 gal tank on my 2013 72. My first tank full I got 40 mpg & the light came on at 100 miles. It took 2.5 gals of gas to fill it. I have a 2" lift kit. So I guess that means I still had 2 gals of gas left inside?

Is there an aftermarket pump that will pick up more of the fuel left inside?

Is there a way to attach a t fitting inside with a hose running to the inside rear of the tank to get more usable fuel?

I was really hoping to get more miles than 100 before the light came on. I'm going to try running it until it sputters & then fill & check the gals needed to re-fill & miles traveled

 

Rob, your bike will continue to run until it empties the tank! You can continue riding after the light comes on, as you do indeed have around 2 gallons of gas left in there. It would not be wise to ride on for 80 miles before refuelling, as there is the obvious risk of running out! However you can and should ride for say 60 miles, to confirm your available range. Just be certain, for the first time, that you know there will be gas available!

 

Rob, or run it dry (carry a small can of fuel with you) and note the miles traveled, and go by that # in the future...oh, and by the way you need to only carry a pint or so of gas with you as long as you are not toooo far from a gas station...a pint should get you 15 miles or so...

 

My iron is the same 95 to 105 when light comes on.

 

When my lights goes on it takes 2.1 gal to fill it on my 3.3 gal tank.

You can't go my mileage as everyone gets different gas mileage. From 30-50 mpg. I, for one, get horrible gas mileage and average in the low to mid 30s.

I have asked and have never received a definitive answer to exactly how much usable gas an EFI 3.3 gal tank holds. It seems to be a mystery. LoL