Hi I'm new to these motorcycle stuff and i just got me a 2003 cbr 954RR last week and i was wondering what kind of oil shoul I use is 20/50 fully synteric work on my byke the owner before me always use fully synteric oil.
please help !!!

 

Here's a few links on motorcycle oils: BITOG, Shell Rotella, Calsi, VFR World. There are many available options & opinions, but you should educate yourself and make your own.
Also, your manual will provide you with the required/desired weight & type of oil (link). Ambient temperature should be a determining factor in weight. 20W-50 is too thick, imo. I run Rotella Synthetic 5W-40 in mine.

 

You can't ask for much more than Incognito gave ya.
Another part of one of the sites he linked you to has a great article "All about Motor Oil" that will also give you some good general info.
I also run Rotella in everything.