Any old shit you can get your hands on will do... within reason. Stick to the required API rating and dump in there what you can get for a reasonable price.
I used mostly mineral (dino) oil and in the deserts of China some Castrol 10w60 full synth because that was what was available at a good price and at 46c with an air-cooed engine it worked aok.

Nothing wrong with mineral oil. Mineral oil NEVER wears out. Only the additives they put in it do. On large ships, they never CHANGE the oil. They sample it and add additives to replace the worn out ones.


John

The problem really starts with the modern practice of using the same oil for both engine and gearbox. They have opposing needs. Gearboxes chew up oils due to the shearing action of the gears.
Because of this the oil "has" to be synthetic, however you lose the longevity of the oil because the engine pollutes it. A modern car on synthetic oil can easily run for 12,000 miles as the gearbox is separate.

My Enfield Electra is supposed to have the dino oil 15/40 changed every 3500 miles. In all probability synthetic would run for double that provided it didn't cause leaks. Contrary to expectations my Royal Oilfield does not leak ?

So I guess you could run for 7K miles if the bike was run lightly loaded without much gear pressure, start reducing this for heavier loads or when you have been using significant amounts of horsepower.