Valvoline, or Catrol motorcycle is the best for the money, only $4-5 a quart. Made for wet clutches and has the right amount of zinc and phosphorus. Rotella and diesel oils work great. As well as any standard 10W40. Honda specs designated regular auto oil back in the day. 10W40 is exempt from the lower zinc/phosphorus levels the EPA demanded in new oils because 10W40 is not used in any new cars or trucks, they all use 10W30 or lighter. So you can safely change your oil with anything other than some of the modern energy saving oils, conventional automotive oil does not contain anything that will ruin your clutch. Confusing huh?
I have run Amsoil motorcycle oil and it actually didn't feel to have as smooth of shifts as Valvoline motorcycle oil. For what ever reason Valvoline motorcycle wet clutch oil has slightly more zinc/phosphorus and a higher TBN than their ATV oil, so its better for the same price. Frequent oil changes are more important than really expensive oil.