Years ago I used to haul my KTM MX bike on a MotoJackRack on the back of my Explorer. For shorter trips it was more expedient than loading up the box trailer. Bike + rack was getting near 300 lb and Explorer was rated at 6400 lb towing 640 tongue, so I was <1/2 the tongue rating. The vehicle's tongue rating is based on where the ball would nominally be, and these moto racks center the weight significantly further back, so being conservative is good.
I also had air assist shocks to level out the Explorer. I could def feel it back there and there was a tendency to oversteer around corners but it wasn't too bad.
For a heavier bikes, I had a friend who towed his Ducati around behind his Jaguar (custom built hitch) using something like this:
Motorcycle Tow Caddy|MagnetaTrailers.com
I think a small rail trailer is all around a better idea.