I'm almost as fat a bastard as you
I'm wondering the same thing.
I seriously doubt this bike I have is going to be anywhere near 40.
I would think foremost, it'd be riding style. Maybe the factory thinks 65 should be the best speed for economizing. I noticed a serious difference between 65, and almost being able to see the gauge move at around 80.
I'm also wondering just how good/bad the seal on the intake manifold has to be, before the bike acts up. I wonder if it's possible to compensate for a slight leak, by running richer, which would make the bike run fine, but kill your mileage?
I wonder just how much one turn of the PMS
is worth in MPG. Could a guy turn that rascal in a bit if he was going to be driving on the highway, and see an appreciable difference?
This came up awhile back, and there was a guy from somewhere out by Scottsbluff Ne. with a stock bike, etc. who had his dynoed out there, and he was getting way up in the 50's IIRC. I seem to remember he said he was running a 160(mikuni? I'm not sure) main