Poor Gas Mileage?

[Bubbafunk32]

1975 CB750F0 24,000 miles
I started out with a full tank, I put 88 miles on the bike and it started losing power untill I hit the reserve I went to the Gas station about 3 miles later and put in about 3.3 gallons of gas I figure I'm getting about 25-27 mpg I did drive her kinda hard but was just wondering if this is typical? The bike starts idles and drives perfectly with great power and throttle response. I am a big guy too about 290lbs
the specs. say the bike should get about 43Mpg but maybe that's with a smaller person.


Thanks

[Re-run]

Well weight of course makes a difference but that sounds a little low. Have you done a tune up recently? If not, you should. Either new points or dress the old ones. Check condensers. Check valve gaps. Make sure timing is on. Maybe a good carb clean. Set your mix and then sync. Another thing is maybe a clean air filter.
Without more info on mods done to the bike, I cant offer much more.