I just bought a used 2004 WR450F. In the box of parts that came with it was the front sprocket cover. I went to put in on and found out why it was off - when I backed out the screw holding the front chain guide in (which uses the same screws and fits under the sprocket cover) the thread for one of the screws disentigrated. These screws thread into the crankcase and have a built out portion which came apart (sort of a nipple looking thing). So - my question is - what is the crankcase made of? Aluminum? I've done some searching on the site and see some potential fixes, but this is going to take more than just drilling an oversized hole to put a new thread in, I'll need to build up some material on the outside of the crankcase.