Yes... but I have it on good authority (a Brit biker riding an 1100) when he was having "problems" of a personal nature which left him virtually penniless and gasless and friendless far from home.
He says he got near to 90mpg by riding very slowly.
His 'problem' also might have affected his perception at the time ... so who knows for sure.
I think the inherant advantages of a relatively modern 4 stroke outweigh the "inefficiency mode" this test would use..... enough to still outdo your typ 2 stroke moped.
And if a big bike like the one I am talking about would... imagine what a modern fuel injected small single tuned for efficiency would do.
(none of them are actually tuned that way as of now.. gas is still pretty cheap)
On the trip thing... I had considered a slow economy test... and I have to say that the discipline needed to stay at say 30mph for long periods of time...(in 5th gear) might be more than I could muster!
... I put on 80 miles yesterday and experimented with speeds on back roads (dirt)... the carb slides were only the tiniest bit off the bottom in 5th gear at 30mph... but I bet I am getting greaaaaaaaaaate gas mileage anyway!
The fuel economy bike that reached 280mpg was a single cylinder Honda 185 with minimal motor mods ... the procedure was to gently accelerate to bout 25 mph... the kill the motor and coast to bout 12.. then bump fire it back up and do it again.
(if I remember right!)