My SV650 Y was feeling like a pogo stick to ride and difficult to keep on line. I replaced the rear shock with a YSS shock, which is really good. I wanted to upgrade the fork oil to something thicker. 15w was widely recommended, so I tried that, but found it similar to stock. I noticed that the viscosity of the oil mostly affected the rebound damping, so decided to try 20w – and it’s vastly improved the handling.
Suzuki SV650 Y – fork oil comparison – stock, 15w and 20w