Normally I wouldn't be too concerened. When I first checked mt valves after the breakin period I had to shim the intake valve next to the cam sproket from 180 to a 190,thats right two shims bigger after only a short time riding. Yamaha paid for the shim but I had to do the work. Not a problem. I put less than 20 hours on the bike last season.I just checked my valves again and I had to go another size shim on the same valve (190 to 195) the rest of the valves are the same as the last check that I did. At least it is not going tight. I am thinking that the valvestem might be mushrooming....Maby. I was just wondering if anyone else is having this problem with their 08' 450. Yamah has a good history with valves in these bikes.