well. mpg results depend on various environmental factors and how fast you drive, as well as the condition of your bike. try filling up your gas tank to whatever level you always fill it up at. GPS a location. Ride there and back, and see how much it cost to refill your tank. GPS will give you distance, and the price of refilling tells you how much gas was consumed. by doing it this way, you dont have to worry about watching for the reserve fuel reserve light. less variables means less percentage of error.

also. check on the condition of your air filter. and has the chain and sprockets been modified?

furthermore, you should not need to add coolant from time to time. if you do, then that means you have a leak somewhere. If you have a leak, then you should to pull your spark plugs (again) and inspect them for white residue, which would indicate coolant leaking into the combustion chamber.

 

also is your FI light on?