I bought my first 450 a couple months ago.. It was an '11 yz450.. After 45 hours, I love the thing.. I still have my smoker, but I know realize the true pluses and minus to both bikes. Don't get to crazy about the thing blowing up.. Just change the oil and keep the air filter clean. I had the valves checked at the recommended 30 hours and they were fine. As a long time 2stroke rider, and 4 stroke hater, here's what i've learned.. - Track is WAY easier on the thumper.. - The weight isn't somthing you will notice.. If anything it can add stability in the rough - There's NO comparison on the low end torque between the 2 and 4 stroke. - I truly believe I'm faster in the open areas of the desert and the bike doesn't wear me out nearly as much - If it fits in your budget, having both a 250 smoker and a 450 valver is the ticket.. I love my 2011 YZ450.. But my 2011 250SX is badass also..