I rode from my hometown in Italy to Jordan and back in 2008, and I can tell you that I had to obtain the International Driving Permit (anyway, I was stopped at a checkpoint between Petra and Amman but the two very friendly cops did not even want to see it).
No need to have the motorcycle's documents translated into Arabic.
Duties: I think you have to pay them at every border crossing but to tell you the truth I don't remember well how it was way back two years ago.
I rode there in August, and I can tell you that Syria and Jordan are really hot (but if I'm here writing to you, it means I survived...
). Drink plenty of water, it will be easy to find it, because gas stations are quite well spread over the territory and they sell every kind of fresh beverage you may need.
WARNING: on August 10th the Ramadan period begins, and drinking in public areas from dawn to sunset may not be appreciated by observant muslims...
It's an easy trip, anyway, don't worry. People are fantastic and helpful everywhere.
Nick and his 2010 Yamaha XT1200Z Super Ténéré