Ooops.. sorry. just read that.. I must have been asleep when I read that.
I'm guessing you take the cap off the side of the adjuster, so that you can access the screw under it.
I'm only guessing, because I don't have a service manual for an RMZ450, but the pictures on bikebandit.com show a large spring inside and a screw holding that presses against the push rod.. Bikebandit calls that screw "9: BOLT,ADJUST"...
I'd imagine that if you loosen that screw, it causes the spring to apply more tension to the pushrod..
Of course I could be totally wrong.
http://www.bikebandit.com/2006-suzuki-motorcycle-rm-z450/o/m9768
click on Cam Chain and you'll see what I'm looking at.
Perhaps someone with more knowledge about the RMZ will enlighten us..