I am refreshing an 87 XR600R and the top end appears to have been oil starved by the PO. He was riding on a freeway for a couple hours, it started getting louder, he shut it off and trucked it home. I pulled the motor apart and there are some parts to replace. one of the ones that is messed up is the head right at the cam center journal. I have read that you can sand this down with 600 then 1000 grit sandpaper and use them like this. or do I need to get another head, or send this out to be machined out for bearing shells?