I am rebuilding my bike, 110 hours on it 2010 yz450, I got the valves out, i am replacing the valve springs, and seals. the valves havent moved since new, so I am going to reuse them, but they have quite a bit of carbon build up, especially the exhaust vavles. do I just leave it? or is there a way to clean them? also, what is the best way for replacing the valve seals? thanks guys, and I did my cylinder with a scotch brite ball on my drill, how do I know when it is honed enough? again, thank you guys.