My new Honda Bike not giving the good performance as told by the dealer.

Location/place: Davangere

Name of company/service: Honda

Hello, i have bought new honda shine bike with disc brakes. It cost about 63000. The main reason i bought that bike is for getting good mileage as told by dealer in showroom.I bought it on Dec 2010, but its performance is worse. Showroom dealer told it will give 75 Kmpl but i am getting only 45kmpl. its performance is worst. I think he has given a rejected piece or some body else used that bike earlier. The dealer is not responding to my problem..