I agree most use 20w50 for engine oil for wide temp use and better cold starting, make sure it made & designed for (4 stroke) motorcycles .
and/or recommended for air cooled motorcycle engines.....
also some oil manufactures like RP recommend 20w50(maxcycle) for engine oil and 10w30(maxcycle) for the primary , but if using other oil from another manufacture go with at least 10w40 or 20w 50 in primary and make sure it for WET CLUTCH USE for in the primary or you could ruin your clutch very QUICK.
definitely reccomend full synthetic oil , like Royal Purple or mobile 1 . USE the best that you can afford , same goes for the filter (oil & air)...
info for oil change in service manuals above.