I got 68 MPG on my last tank. I'm running K&N filters (OIL and Air) M4 Carbon fiber, a PCIII and a 520 Supersprox with stock teeth front and rear. I ride for fun not to get anywhere. The valves are good and she has fresh plugs. I try and avoid traffic. I also avoid stopping. The roads around here are smooth enough and clear of cars (mostly) so that I can slow down and wait for a red light to turn green.
Even when I'm trying to go 5tuPiD Fa5t, I get almost 50 MPG. I check my tires twice a day, minimum. Once in the morning and again before I stop for the day. I also check before I ride if it's been more then half an hour since I got off.I could get better but I try not to let the RPM's get below 5K in town. I will roll along in 6th at idle when on a back road going from nowhere to noplace. The cows trot alongside and we gossip. That is how I prefer to ride. What I consider fun is going 50 miles or so on the back roads at 30 MPH or so, then finding the Interstate and running for home as fast as traffic allows.
If you are not getting around 50MPG, you need to get a tune up and check your tire pressure.