If you are burning valve seats, you have another problem. I suggest a weak valve spring, or a faulty compresson release mechanism. I assume it's the exhaust valve?
To do this work yourself, you will need a valve seat cutter, which is not a piece of equipment most DIY mechanics posess.
I pull engines apart all day, but this is one job I leave to the machine shop.
phil_saunders@bigfoot.com
Phil Saunders, August 2008