So I calculated my bike's fuel economy and here are the results.
I filled the tank of 800rs petrol.
1 litre costs 113 rs. This means 800/113=7.07 litres came in the tank.
The reading on the odometer was exactly 166.6 km when the petrol finished in the reserve tank .
So 166.6km/7.07 litres=23.6 km/l.