loss of power?

[biggie400ex]

ok...I recently had to replace my vavles. I just got my quad back today and it seems drasticly slower. Maybe its just me since I haven't rode it in 4 months, but it just seems slower. I can't see just replacing valves that would cause it to be slower. Anything the guy could have done that would cause this?

[Stonewall 61]

are they adjusted correct? if there was too much play, the valves wouldnt open are far as needed to make it run proper.......