Not new to 4 strokes, just to the 07 YZ450F. Last YZ I rode was the YZ 400, last 4 stroke was the XR 400. I just traded my Kawasaki Brute Force ATV for an 07 YZ 450F because I found out I could not adapt to 4 wheels, and speed on an ATV that weighs 650 lbs can kill you, and almost did. So anyway, when talking with my son, who I converted over to a 4 stroke fan, he said that the YZ would be much different than the XR. He said that there is a great deal more preventative maintenance that needs to be done, such as adjust the cam chain and valves every 10 rides or so. Is that correct, does it really need the cam chain and valves adjusted that often? I will not be racing the bike, just desert and trail riding. I do ride a bike hard and fast though. Please give some advice to a guy that used to ride the bullet proof XR 400 that only required attention to the oil and air filter. The YZ 400 definately did not like trail riding in the woods, the engine torque would constantly try to put you in the trees. Is the 07 YZ 450 a little tamer on the bottom end? How many guys use theirs for trail riding without regearing or fly wheel weights?