use rv trailer hitch to carry 320 lb motorcycle

Even if you had the bumper beefed up enough to carry it, the weight would throw off the balance of the trailer and lighten the front so much that sway would likely be a horrendous problem. TT's just don't like having that much weight imbalance. You can often get away with it on a fiver though.

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I have a small dual sport (225cc Yamaha) that I thought a lot about doing exactly that. I elected not to do it due to the changes in the driving dynamics of our fifth wheel. You would also have to really reinforce your rear bumper. I just didn't want to take the chance.