20W40 with no friction modifiers is what is called out for my XJ600s
SAE 10w30 oil or Yamaha 4 Stroke Engine Oil
Some of the Yamaha motorcycles that came out in 1986 are: FJ1200, FZ600, FZ750, XJ600, XJ700, XS400 and YX600. The YX600, also knows as the Radian, was the most affordable at that time.
Yamaha's Yamalube, 2 stroke oil is a good choice.
sw 30
Yamaha's Yamalube, 2 stroke oil should work pretty good
Yamalube motor oil
Yamalube motor oil.
2-Cycle Engine oil.
a good quality 2 stroke oil
Yamalube motor oil
I use 10W30 in my 1989 Yamaha Warrior.
Lance's Haynes manual says: Capacity: 555cc, Type: Yamaha fork oil "01" or equivalent