I've installed probably 40 of the CRF450 kits from Kibblewhite and it's by far the best fix out there for the valve recession problems. A good valve job and the Kibblwhote kit will give you a nice stable valvetrain that will last. Depending on who you talk the Kibblewhite kit (valves, springs and titanium retainers) a complete valve job, installation and setup of the kit should run in the neighborhood of $500. It should be about $100 or so less if you don't need a valve job, but it's usually a bad idea to put it together without touching up the seats.