Obviously the 2nd Gen B6 is a little less thirsty...
20 litre tank lasts usually 350km. If I am on the throttle lots, keeping the revs in the 7-10,000 range (and having fun!) the mileage drops to about 290-300km. OTOH if I'm all day with my cruiser buddies, at 90-100 kph, I can get as much as 450km. (On one trip I refueled at 430km, and was not yet on reserve!). However, this is a stock 2G B6, running with the stock lean jetting.
So...17.1 km/litre, 49.4 miles/Imperial gal, 41 miles/usgal