On the Drifter 800, there has been reported problems of the bike sputtering and behaving as though it were running low on fuel despite having full tanks.
The situation could be either overfilling the tank resulting in vent blockage and vapor lock. Or a blockage of the gas cap/tank venting system.
You can verify vapor lock by stopping and opening the tank when the bike starts sputtering. If the bike's engine returns to normal, you know you have a blockage.
Ensure you don't overfill the bike. Level should be below the neck spout.
You can also blow out the gas cap vents, using a straw. Sometimes water, fuel or something solid will obstruct the vent.