The YFZ450s had a problem with this. The seal on the pump side would wear out but the one on the engine side never had any problems. Some of them would quit leaking after it warmed up, you will just have to try it to see. A grove would wear on the pump shaft of the YFZ also, so if you replace the seal, I would check the pump shaft also.
2008-Holz a-arms, stem, flex bars,Uni,SR4,FMI,Web cam,Fox shox,Rath nerf-bumper,ASV
2011 xmx -Fox Shox, dual exhaust cams,Uni,SR4G2,Rath nerfs,DWT,gripper seat
[B]2012 xmx[B] Full rossier build