I bought Yamaha SZ R in 2nd half of December 2011.Until the first service mileage was just 38-39km/l against the company claimed mileage of 65-70km/l. after the 2nd service done on 04/04/2012 my bike is giving a mileage of just 27-30km/l. It is just 4months since i bought the bike. Please guide me how to get a proper mileage now? is it possible to replace the engine with warantee?