I'm going to try the good ole fashin'd way of topping it right up, running it for at least 120-50 miles and then topping it up again.
Compare actual liters used to computer reading and repeat excersise to try and work out if there's any semblance of agreement.
The average mpg v miles done / fuel put in seems to agree. Filling to the top of the neck from the light gives 14.3 litres. Not been brave enough to see if I have an extra 2.3 litres or only 1.7 litres to cough / splutter / pushing the bike. Have about 40 miles to go on the countdown, with an average 64 mpg or about 14.5 miles per litre.
HTH


