check the manual here. page 52 of 77, just below #10. Quantity (each front fork leg) 476cm3 (16.09356 US oz). Recommended oil: Yamaha fork and suspension oil 01 or eqivalent.
as to what the weight is, I dunno. but if you click on the pic below, it will take you to Yammies site where the 01 stuff is sold. they also have other wieghts if you click on the second pic. if I were a betting man, which I'm not cuz i get killed at the casino's, i would venture a guess as to it being 10wt since they offer 5, 7.5, 15 and 20 weight oil and thats right in the middle of their offerings.