Consistently when I get down to my last two liters of fuel, Honda seems to have got it right without litigation.
By this time the fuel light has been on for awhile. For me, this signals to "be easy" on the acceleration / engine revs. In addition, the last flashing fuel gauge bar extinguishes. This should signal the alert rider that "time is up" ... all bets are off hereon in.
This has been the case for me on the 2019 AT about 10 out of 10 times.
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In addition, the 2014 Honda CB1100A and 2018 Honda NC750XD exhibited the same reliable behaviour (NC more so) in regards to remaining fuel range during the same travel routes used with the Africa Twin. NC refills discrepancy was always within about 100 mL of fuel.
Though not as relevant, my 2009 Aprilia was surprisingly accurate - and I believe more so than Honda. The fuel tank was below the seat (as it is with the NC750X) and doesn't have the challenge that
@AT-Dragon outlines previously since it funnels all fuel to the pump.
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I believe Honda has done a reasonable job warning the rider of fuel conditions. If the rider is inconsistent or heavy-handed while low on fuel, then variations should be expected.
In addition, strong headwinds or too many inclines will also non-linearly run down the estimated remaining range since its affect on average fuel consumption is latent.