batwing mower bucks violently! need advice

I bought a CTL batwing mower that is about a 12 foot cut. 4 cylinder Kubota I think. It bucks so bad at full throttle that it almost throws me off. At about throttle it does better. I've only had it for one day and wonder if the decks are dragging or an adjust needs to be made? It doesn't seem like a good thing to run it at half throttle. Thank you