So it was really nice weather here today and I wanted to ride and do a little experiment. Like the subject line says, I ran out of gas on purpose.
Last year I ran out by accident (hadn't set the odo, was on a steep downhill, etc.) and wanted to now know how many kms/miles I can do on a tank.

Weather, Sunny and 15-17*C (~61*F) + breezy....about 120kms (75miles) put on the bike today)
Bike 2004 RKC TC88, stock.. Solo Rider 200lbs..with gear? 210-212lbs likely.
Fairing and Tourpack and soft lowers.
Most of the miles (kms) on this tank were put on around 100-110km/h(65-68MPH) speed (adn between 7C-17C(44*F-62*F). but some were as low as 50-70km/h(+/-40mph)
Some spirited riding but mostly at speed limits, rolling hills + flat stretches. No revving at stoplights ! (LOL)

Gas Gauge seems fairly accurate. I usually try to squeeze in as much fuel as possible, but always with the bike on the stand.

At 307.5kms (191miles)on the trip, the low fuel warning light came on.

30kms (18.6miles) later I got my first sputter as I was coming down a very very slight hill out on the hwy, doing 110-112km/h.(69mph)

At 31.5kms (19.5miles) I decided to pull over as it was sputtering hard, then running good etc and a very technical section on the road was coming up with virtually nowhere to pull over. Maybe I could've potentially got more distance, but I was very very close to empty. Gas gauge read empty.

I pulled over and put 4L (about 1 US gallon+ a cup or so) from a Jerry can I had on the tour pack rack and gauge then said about 1/4 tank. Bike cranked a little hard, but did start.

I use premium fuel, always. Octane rating...hmmm, not 100% sure if I believe it, but it's purported to be in the 91+/- range.

So, aprox 339kms (210 miles) on 1 tank before empty.

As always (literally) YMMV

Worlds biggest potato?

 

Good man and thanks for your sacrifice, in the pursuit of scientific evidence. We get so much discussion around HDF on fuel consumption it is just great to find someone who has done something so simple and yet definitive. This thread should be a Stickie....

 

Thanks GR. I am a technical type guy, so tried as best I could to state all the variables, to insure folks realize this isn't a hard and fast rule that your bike will run out of gas at XX miles/kms, but this is what I did and my results.

 

but, as your bike is a 2004 with a tc88, your results are inconclusive. in order to maintain scientific accuracy, you are now going to have to go out and buy a newer bike, say a 2007 with a tc96 and a 6 gallon tank. and a tc103. don't forget the cvo 110. and then of course, a 120r is going to be needed. plus, the new m8s, a 107, 114, and 117.

all in the name of science, of course

 

It's interesting you did it that way. I guess knowing for sure is worth, well, knowing, so that's cool.

I did it the lazy way. A couple of times I've filled up when the gas hits "Low Range" (a newer bike thing) and it almost always takes 5.5 gallons. At 40 miles per gallon on average, I had about 20 miles left until actual empty.

 

But what is the point of "how many miles", since gas mileage is a variable here? What matters is "usable tank capacity when filled to the highest point H-D recommends"?

I can tell you for a fact that my 2007 Road King (same five-gallon tank) really DID hold five gallons. I was running on fumes and it was sputtering when I pulled into a gas station and put 4.96 gallons in it, to the bottom of the filler neck.

So now I'd like to know what the usable capacity is on my 2017 Road King and 2017 Road Glide Ultra. The "miles to empty" feature seems flaky to me . . . one starts at 61 miles to empty and within 20 miles goes to something like 30 miles to empty . . .

 

So, are you gonna fillup at 200 miles from now on?
Why not, that leaves you with 10 miles to spare...

 

The irony is, the extra weight/drag of the full jerry can probably reduced your range....

 

I'm really curious at what point my 18 would run out. I can go 240-300+ on a tank and remaining shows less than 10 miles yet when I fill up it always only holds 5.1 gallons.

 

I'm waiting on someone to post something that just blows us all away with His brilliant gas mileage...