Some wet-clutch manufacturers sell 0W- and 5W- weight oils as well as 10W-30 oils which meet wet clutch ratings (JASO-MA ratings). The viscosity numbers only refer to viscosity, not the qualities used to determine suitability for wet clutch operation.
Any old oil may work much of the time; the correctly rated oil will get you beyond "much" of the time, closer to "all" of the time.
Someone already mentioned if it has a wet clutch make sure you use an oil with the JASO rating.
Make sure it is not only JASO, but JASO-MA. The Japanese Automotive Standards Organization rates oils in various ways just as other oil rating organizations do.
