I used to tow my dirt bike on the back of my '63 Dodge Dart many times. I bolted a piece of channel iron to the bumper. removed the front wheel and slid the axle thru to holes in the channel iron. Tie downs from the handle bars to the ouside of the bumper kept it vertical. It would be best to remove the chain from the rear sprocket and tie it out of the way. If you don't do this the transmission can easily sieze since it isn't getting the normal lubrication. Backing up can get pretty hairy because of the fork angle so being able to see the bike while you back up is absolutely necessary.