Here is proper way to rebuild Kayaba fork and change oil seals. This fork is used on many motocoss and enduro bikes: CRF250, CRF450, YZ125, YZ250, YZ450, WR250F, WR450F, KX450F, KX250F, RMZ250. Procedure is not complex but need spesial tools and time. If do everything right, the fork works for a long time.
Suprotec: https://suprotec.ru
Sorokin tools: http://www.sorokin.ru