Can the tank from a Honda 900 F 919 be easily connected onto Nighthawk?

No, the tank from a Honda 900 F 919 cannot be easily connected onto a Nighthawk. The 900 F 919 has a different frame and fuel injection system than the Nighthawk, so the tank would not fit properly and would not be able to be connected to the fuel system. Additionally, the 900 F 919 has a different seat and bodywork than the Nighthawk, so the tank would not look right on the bike.