Oil threads come and go every year, I guess because people just can't understand that the cheapest oil out there actually works better than just about anything else on the market at any price.
I like the Rotella synthetic 5W-40 best in two of my bikes (they seem to run quieter with it than the standard Rotella). The standard Rotella 15W-40 is used in the other bikes, or Mobil Delvac 1300, whichever one is on sale (usually one of them can be scored for less than $15 per gallon). All three of them are heavy duty diesel oils with lots of zinc and phosperous, which is what any wet-clutch really wants to be fed.
Advance Auto parts also has a generic version of Rotella 15W-40, which is usually about $1-$2 less than the Rotella, and seems to be the same stuff. When it's on sale, it goes for about $12 per gallon.
If you use one of the oils listed here, you can rest easy knowing that you aren't wasting money, and any engine issues you might have aren't going to be oil-related.
Arggghhhhh !! Fifteen dollars a gallon ? I hate you !!!