My buddy jokes me with this bike. I have had it for three months, put 4.2 hours on it, and checked the valves 4 times. LOL! They are at-intake .110mm all three, exhaust is at .208 across both. That is what it was when I got it and they haven't changed. I know it's not required to check them that often but I wanted to make sure they were not needing replaced. I bought the bike very slightly used but it is an 03. The original owner had service paperwork with oil and air filter service and I could tell the valves had been checked at least once, but the cam bolts did not look like they had been removed, so it is doubtful they have ever been shimmed. This is my first motocross 4 stroke and I actually prefer the two stroke 250, but man those are hard to find. As I ride this 450, I get more and more comfortable on it. It's just the thought of dropping a valve and busting everything up that makes me cringe. I do my own engine and maintenance work and have a shop here that I can do it all in, so that is not the problem. It's just that thought hanging in the back of my head every time I start this thing.