Hello, I just recently bought a used 2007 yz450f and it has gone through two owners. The owner I purchased it from said he used it to race through the desert and had to sell it because he dropped it and broke his wrist, therefore not able to work and needed cash. I have absolutely no experience with these new four strokes, as I have only been familiar with quads before. I plan on taking it to the local motorcycle guru but I need your guys' help as to what I should have them check out to ensure that the life of this motorcycle is a long one. Obviously I've been reading and reading and downloaded the manual, but from personal experience I'd like to hear what you have to say. Thanks for any help! List I've come up with: Oil and oil filter Air filter clean/replace (PO said he uses NO Toil) Loose bolt on the left side of the inside of the swingarm but I cant take it out because the sprocket is barely blocking it.. What is it?