i recently took a trip to the dunes on my 08 yz450. i purchased the bike back in april and took the time take the bike through its heat cycles, and give the engine plenty of time to break in before i started riding it like a dirtbike... i was told by the service tech and the dealership that it wasnt all that important to bring the bike in for a first service if i was willing and able to change the oil and filter and tighten the chain and lube everyting up. all that is a very simple task, however i am new to the 4stroke revolution and have always owned 2 strokes, so i asked him about the valves and he told me not to even worry about them till i have at least 50 hours on the bike. and i do now. while i was at the dunes i noticed that engine having to work way harder in the sand than on dirt and i slowly noticed the engine developing a tick mid to upper rpms... in my mind, the bike had always has a high speed tick that ive noticed out of all 4strokes, and i am assuming that the sounds is caused my the cam hitting the valve buckets... correct? and the sound that i am getting out of my bike is in tune with that same tick ive always heard, it just steadily got louder.... does this mean that it is time for a valve adjustment? and is the louder tick caused by the extra space between the cam lobe and valve bucket?..... i could have just been thinking about it too hard, but it seemed like the harder and longer i rode the worse it slowly got, and the bike seemed to loose a little bit of ummppff it the mid to top rpms... would out of wack valve rob the engine of some power as well!?... ANY help trying to understand this would be great!