I was reading the rmz forum and they said that the yz valves can only be re seated or something like that only once? That make any sence? IDK what that means if anything BUt how often will I have to rebuild a yz if I get it? I am going to get a 450 just having troubles between green or blue. Do they have to get rebuild often? I am not an mx racer i do ride woods and am going to do hares. thanks also what will it cost?