2011 yz250f fork oil capacity?

Check your owners manual, it will be there. Race Tech recommends 350cc.

For KYB twin chamber forks the spring seat has very large ports and the oil can flow through fairly unrestricted. The positive of that design is the fork is very sensitive and supple, but the compromise is in bottoming performance. It lacks bottoming control a lot compared to the Showa and WP spring perches.

Because of this the manual probably recommends running a higher oil quantity of 370cc if using stock springs. If you are using one or two spring rates higher then you should drop your oil height approx 10cc.

Riesenber is not incorrect, as 350cc would work just fine. 370cc would just work better for that style fork.