I had purchased honda dio but fuel average very bad less than 40 kmph waht to do?

New dio please helf me to increase average how?

If you mean 40 kmpl, tha's kilometers per liter, then you are under what the manufacturer says you should expect, which is about 65kmpl.

A new motor takes time to break in and as it does break in, you will see better and better mileage over the first 10,000 kilometers you put on the bike. But, even that won't make up 25 kmpl difference.

Are you riding responsibly? If you constantly run the bike at wide open throttle, you won't get good mileage. If you always accelerate at full throttle, you won't get good mileage. If you always carry a passenger, you won't get as good mileage. If you weigh 300 pounds, you won't get good mileage on this bike.

Are you figuring you mileage correctly? Total kilometers divided by liters of gas used to go those kilometers is how you do it. The bike holds 6 liters. If you ride 300 kilometers and put 5 liters in to fill the tank, you are getting 60kmpl mileage.