I'm making the assumption this is for a Gen1, as you don't state this.
The
Yamaha service manual is available to download from the Downloads section.
Each leg should have 440ml of fork oil, the air gap should be 140mm measured from the top of the inner tube and damper rod, with the tube fully compressed and without the spring. K-Tech advised me that this would be the same with their springs as with the OEM.