Just thought i would share with you all a very peculiar problem that i had with my 08 yz450f. Noticed that if the front wheel was off the ground and i span it by hand that the brakes were dragging. The wheel would spin maybe two revolutions then stop. You could see that the brake disc was blue with all the heat that was generated and the bike handled differently. Finally after trying many things i swapped out my friends 09yz caliper, master cylinder and the brakes worked fine. So i knew this was the problem and put my caliper back on the problem reappeared. I tried loosening the bleed screw to see if there was trapped brake pressure and this made no difference. So i changed the caliper seal kit as per the Yamaha Manual and this solved the problem. I've owned roughly 40 bikes and i've never seen this problem and very few people i talked to had heard of it either. A great bike otherwise. the best i've owned yet. Once you replace the muffler..