Maybe coasting down a hill?

But seriously, I've never heard of anyone averaging 70 MPG on any Sportster. Not saying it couldn't happen, but many reports I've read show them not getting very much additional mileage over the 1200.

My 1200C (with higher performance Screamin' Eagle cams that flow more fuel than the stock cams) averages right at 50 MPG.

Under the same riding conditions my EFI Softail FatBoy (with Screamin' Eagle Race Tuner and a good Dyno Tune) averages right at 48 MPG.

My heavier EFI Road King (with a full V&H exhaust and good tune) gets 44 to 45 MPG.

Mileage really varies depending on your riding conditions and the bikes state of tune.

 

I came very close to 70mpg once. I rode the 444 mile Nathez Trace Parkway. (I don't recommend this, very dull ride) 50 mph speed limit, that you had better take seriously, because the Federal Park police do, and it's about a $500 speeding ticket.

The ride is basically flat, just a constant 50 - 53 mph, very limited access. I averaged 67 mpg on that trip. Other than the one instance, I've never came close to 70 mpg.