I would never take a kid on the back of a motorcycle. Unless I really really had to. There's just to much risk in it.

But on topic Me 135lbs and wife 140lbs have rode 2-up enough and it does ok. Just taking off from a hill kinda sucks. You gotta give here a lot of gas.

 

My fat @$$ (200#) and my wife at 140 both rode ok around the neighborhood and that is with having the rear adjuster under the seat set at #3. It was fine and have plenty of get up. I would not recommend riding with two consistantly, but even if it is a few pounds over, if it is not over a long commute like two hours or so, I don't see it being a problem. You will loose a little bit on the higway most likley when you hit close to 75 or 80.However, I don't plan on doing over the speed limit with two people on such a small bike.

Bryan

 

ive riden 2up on a 08, about 340lbs between the two of us. rear shock was on the 3rd possition. i didnt have any problems, except the steering was a little light at low speeds. I never went on the freeway 2up though.