I recently got back into dirtbike riding after having quads for a few years. I got a 99 yz400 with what Iam told is a 2001 426 motor, All I have to say is WOW. I cannot believe the amount of torque these things have!! This bike is SO much fun to ride. My question is, how can I tell what year the motor actually is. I know its a 426, I just dont know what year it is.