I am writing a paper for my 101 eng class:prof: , and we have to compare two objects or things, whatever. I chose to compare the 2008 Yamaha WR450F and the 2008 Yamaha YZ250R. I was going to do a cost of ownership breakdown of the two bikes as part of my paper,so i was thinking about including basic maintenance costs as well as the cost for a basic top end rebuild. However, I have little to no experience with four strokes, so i was wondering if some one could give me a list of parts associated with a basic top end rebuild. Thanks in advance.