I have a Bajaj Discover 100 (5 Gear) model manufactured in 2011. I bought it about a year and a half ago and it was doing about 50kmpl. But now the fuel consumption is around 35-40kmpl and hill climbing performance is significantly reduced. black smoke is coming while accelerating at idle position. It was a lot in the beginning, but now it is less due to a recent carburetor adjustment. Also, I heard this model should perform an average of 65kmpl.
Since I did the carburetor cleaning and adjustment, what could be the other possible reasons for reducing fuel consumption?