I have an 06 YZ 450 and just took it out for the first time this weekend. Well no more than 15 minutes into my ride the mixture screw fell out of my carb and my bike ran like crap. Well i really wanted to go riding so i borrowed the mixture screw out of my friends 05. Turned it 2 turns out as per the manuel says and again like 5 minuties into my ride it fell out again. The screw is under tension with the spring so i cant understand why it keeps falling out. Anyone else have this problem?