[JRTJH]

Travel trailer bumpers and frames are typically NOT structurally strong enough to support that much weight. Most have difficulty with 100-200 pounds. Adding a receiver MAY provide more reliability (as far as strength goes) but opens up another concern. That is hitch weight and maintaining the appropriate 10-15% of total trailer weight on the hitch.

Between the strength problems and weight (balance) problems, I'd be very reluctant to try it. Four hundred pounds of motorcycle PLUS the weight of the receiver and the mounts is going to add up to a total weight of 500 pounds or more.

As an alternative, I'd be more inclined to look at finding a way to either carry it in the truck bed (adapt a rack to carry both the ATV and the cycle) or consider a rack on the front of the tow truck.