Try this and see if you get better mileage. Fill the up and take a ride. Do your best to not let your rpm's get above 4,000 on the ride.
Then fill up and do it again with 3,500 rpm as your max.
Next make 3,000 rpm as your limit. I bet you'll start getting some impressive numbers.
I just rode 60 miles with a 3,000 rpm limit and it took a lot of self control not to open it up.
If you set limits, its not so bad because you can enjoy the scenery along the way.
^^^^^^^ What turbo said!
On most rides my engine never goes above 3500. I can take a 2000 mile trip and easily never go past 4000 RPM. That's a big reason my mileage is good. It doesn't take self control; it's how I like to use this engine.