well, did your bike come with a manual (if you bought new) ?
if so, on the 1-3rd page it should tell you what oil is needed.
but, in short, any brand of oil is ok, as long as its not coles home brand, or that black and gold noname crap. just make sure it is NON synthetic.
semi and fully synthetic oils contain friction modifiers and after a while, can cause your clutch to slip.
also , make sure the oil is 10W40, it seems to be what these horizontal pit bike engines like.
Another thing,
this being your first oil change and all, i think it would be a good idea to check your valve clearances. horizontal pit bike engines run best with .003" on the inlet, and .004" on the exhaust.
here is the best video explaining how to set valves
[video=youtube;QJciyJRJh8Q]http://www.youtube.com/watch?v=QJciyJRJh8Q[/video]
